Maybe they should just improve their product to make it more resiliant, rather than blaming customers for thinking that 148 V is below 150 V? Not everybody buying these has a Ph.D. in physics and if it says 148 V on the label and 150 V on the other label then it's your product that has a problem, not the customer.
And no matter what happens, customer support should help the customer, not blame them.
This is 100% on the manufacturer if they intentionally chose to highlight the "best case" 150V, rather than the 120V lower end. Especially without any additional safety mechanisms.
The article presents it oddly, it's not that the converter maximum input gets lower, it's the solar panel output that gets higher from the nominal quoted value (which is not a maximum, and not really intended to be used as such). Derating your converter is equivalent for the purposes of ensuring margins, but it implies the issue is in the wrong place.
The failsafe circuit to protect against this (over voltage condition) is maybe $3 and incredibly routine in anything with power. I would bet everything that it is in there.
What's most likely though is that the fuse is also internal, and externally the unit will appear bricked.
While in general most parts will work beyond their ratings to at least some degree, this isn't really a safety margin. A safety margin is known, rated, and validated, and usually a property of a system as opposed to just one part within it.
Your converter doesn't need to like the voltage, it just can't break from it.
In fact, if it's the type that shorts the panels for curtailing, it should be happy to just run them at the highest voltage it's comfortable with, loosing a few percent generation during exceptionally cold days.
Even that interpretation would be be wrong because it can and it does and the circumstances are very clearly described. Every inverter worth considering for a home installation has this capability. Only really old ones are not able to disconnect from the HV side when things are about to go pear shaped. If I had an inverter without that capability I'd get rid of it immediately because that's an accident waiting to happen.
Open circuit voltage is _very much_ widely considered to be the maximum. If its not spec'd openly as " at temp X" then it's reasonable to expect it to be invariant.
But that's not true - V_OC for PV modules is nearly always spec'd at STC or NOCT, which is clearly stated on module datasheets along with the temperature coefficient of that voltage.
It doesn't matter if it's true. And those spec sheets aren't what you'll find on amazon products. I looked at them, didn't see any mention of temperature. Also, stupid things use XT60 connectors. Not remotely appropriate for 150v DC.
I believe the vendor here produces both the device and the panels being plugged into it, and while they also supply other vendors' panels, they seem concerned primarily with customers who buy all components from them and then experience this failure.
I agree the labeling is an issue here, but the solution must come from the wider industry or regulatory bodies; the alternative is for vendors to switch to their own pseudo-units to internalize the math, which would not be good for customers either - think "ACME Generator2000 accepts up to 4 Power Units of input; each ACME SuperEco Panel supplies 1 Power Unit, or 1.5 Power Units if you're in Canada...".
Saving users from having to do a little thinking to not brick their device is a tried-and-true excuse for vendor lock-in in our industry :).
Why not label the panel with the maximum possible voltage that it can produce? Or even have a little table showing the maximum possible voltage at various ambient temperatures. It's not as if there isn't room on the back of the panel for a big enough label.
This is information is generally stated on the module datasheets, which specify the Open Circuit Voltage (V_OC) at Standard Test Conditions (STC), and then provide a temperature coefficient for how that voltage changes with temperature.
'Maximum voltage' is very arbitrary as this is directly dependant on the lowest expected operating temperature, hence the industry has landed on stating these values at standardized conditions (STC and NOCT) allowing for direct comparison.
The label on the modules themselves tend to also provide these ratings at STC, e.g. this label from Jinko specifies the Open circuit voltage and also summarizes the conditions assumed for STC:
While I agree that the label could also add the temperature coefficient, I'm not sure if it's reasonable to expect that specialist electrical equipment details all of its operating parameters on an attached label without the expectation of consulting a datasheet or manual. For specific products that primarily target non-specialised consumers however, a different labelling approach may be warranted.
That is in fact useful information to someone that needs that info, because it means they should never eat it. I think this is a bad example, because I have no idea what you're talking about.
There's hiding complexity, and then there's creating fake reality for people.
As it is, panels are gonna produce variable power depending on the weather. Putting interoperability with third-party panels aside, to get the simplicity of "max 2 panels in series", they'd have to either cap the max power on the panel/generator link and dump the excess, or set the limit based on the worst case a customer is likely to encounter. I.e. they're either gonna waste power, or gouge their customers for extra hardware. Neither of that makes sense for an ecological product sold to a price-conscious customer base :).
The problem is that you run higher voltages with the same hardware if your in Alaska than if you're in Florida.
Substantially so.
"Wasting" those 5~10% during severe winter conditions isn't worth splurging on the voltage converter.
Though then selling units that suggest to not run a few hundred volt strings before paralleling instead does sound bad, as the string doesn't need separate fuses rated to many volts DC.
Considering the electric code has an 80% rule for loads, anyone assuming they can use 100% of what is on a label probably should not be doing electrical work.
I agree with you, but. The NEC has an 80% rule for continuous loads (over 3 hours) that use a typical circuit breaker as overcurrent protection. If you use fuses or a 100% rated breaker as your over current protection, then you can use all of the available ampacity. Anyways, devices that use a 15A receptacle (for example) will not draw more than 12A continuous if they’re meant to run continuously (3 hours or longer).
No, you just shouldn't assume that that's the case. In the case of a computer and mains, both of those are nominal voltages and there will be a range of voltages which are expected to function, and if you want to check for sure, you should check those ranges.
The point is, voltages are usually a 1:1 match. That includes when you're working with ranges, you want the supply range to be inside the load range.
And even for amps where you see that 80% rule, that's for keeping the load smaller than the supply. Solar panels aren't a load and don't work that way.
This feels a bit like the logic behind "do not put hamster in microwave" warning labels.
I think if you work with electrical or electronic systems in practice, you learn pretty quickly to respect tolerances and that data sheets are a map, not the territory.
Also, electrical installations are usually seen as a field that should be done by trained personnel, not arbitrary laymen home owners. So I think the appropriate reaction would be to remind people that they should hire an electrician to do the installation, if they don't have the necessary specialized knowledge themselves.
Actually if "you work with electrical or electronic systems in practice" you get pissed off at everything for how dumb it all is: 12V DC batteries are more like 14 nominal? AC wall plugs dip voltage when printers turn on, random equipment you arent even sure in the building can trigger UPSes based on unknown settings in the device? International standards and communication protocols mean nothing as "a standard" because each company has their own entire list of bugs/implementation mistakes. All the international enforcement certifications care way too much about inconsequential bullshit and miss all the true showstopping problems in most industries?
This world is amazing anything runs at all. The slightest addition of complexity is causing everything to fail now.
Modern computers are less reliable than ever, some companies have decided to REMOVE the pinhole bios reset (that has been around for 30 years) at the same time as things are buggier now and dont boot again until you physically unplug the bios battery deep inside and hard to get to.
This is what makes software engineering so seductive, everything works exactly as it was designed to (whether intended or not). Imagine trying to program for computers with memory that drifts values progressively more as it wears down.
So on the one hand we have a product which isn't even remotely designed for the use case (hamsters), and during normal use shows obvious behaviour (cooking) that should imply risk to said hamsters. On the other side, we have a product designed to be installed in an electrical system, and shows no signs during normal use that it's installed unsafely, and where the advertised specs are not actually safe for normal usage.
Whether or not the company in this case shares some or most of the blame with novice users - the analogy is not a great one.
I have the impression these are consumer products so I would them to be designed to be installed by people who do not normally work with electrical systems. If they are only sold to tradesmen that would be different.
Yeah, it would be important to understand who the company is intending to sell to or do the installation.
Though the lines are often blurred, because I guess most companies would like to sell directly to end customers, even if their product requires a professional to install.
Even IKEA does this. You can go in and buy an electric stove and oven, grab them from the warehouse and take them home with you right there. But it's a bit of an illusion: You're still supposed to call an electrician to actually connect the things.
> Yeah, it would be important to understand who the company is intending to sell to or do the installation
You can do that by just reading the product page[1]. The delta pro, the equipment in question, looks like a plug-in appliance. It visually communicates that it is portable (by having a wheel and a handle) and by virtue of having a power lead connect to it it communicates that you can just plug it in. They further reinforce this by writing this: "Plug & Play home backup solution". "Easy installation with completely pre-wired Plug & play home backup solution" "The solution provides a convenient home battery system without rewiring or running dangerous extension cables through your home." "Plug directly into an AC wall outlet and make sure that the wall output current is more than 15A."
And on top of that the manual[2] makes no mention of needing an electrician.
In contrast an IKEA electric oven's product page[3] states this: "No plug is included. Installation to be carried out by a qualified installer." and then the manual[4] states "Installation, including water supply (if any) and electrical connections, and repairs must be carried out by a qualified technician."
But of course nobody reads the manual. The big difference is that one comes with a plug while the other doesn't.
I don’t know about the components they’re selling, but with electronic components, it’s on the buyer to properly read the data sheet and understand what the quoted nominal specs mean.
Unless it’s safety critical, you usually don’t want a system with a bunch of active electronics to prevent someone wiring it up wrong, because those components will interfere with whatever you’re hooking it up to, such as the MPPT, the battery, or whatever else.
This is like how AA batteries have a nominal voltage of 1.5V but the actual open circuit voltage is 0.9V~1.65V depending on charge level, temperature, etc. If you connect an AA to something that’ll explode at a voltage of 1.55V, that’s on you.
Similarly if you buy a 470 ohm resistor, you will find in on the data sheet that’s usually at 20°C. To know what it’ll be at any other temperature, you’ll need to use the temperature coefficient to calculate it.
In your AA batteries analogy, this is like saying that you do not need to state that the device exploding at 1.55V would do so, not about battery declarations (panels in this case).
It wasn't meant to be a direct analogy, just a simple example of how you get similar situations in general with electronic components, or really any kind of non-standalone component in most industries. Another example is fuses: a fuse rated at 20A will not immediately protect the downstream once load exceeds 20A, but rather, there will be a curve defined with respect to its nominal rating which defines how long it will take to burn out for any given current and ambient temperature. You may find at 20C, it will not even burn out at a continuous load of 25A, and at 30A it might take 2 hours. So if you're buying a fuse to protect a sensitive downstream circuit, you need to take that into account and use a fuse that's nominally smaller than the load you're running.
Essentially the "nominal" behaviour is not the actual behaviour, it's just a quick way of summarising the characteristics in a way that someone familiar with the class of item will be able to understand what they're buying. Another similar situation is timber sizing, where a 2" by 4" is actually 1.5" x 3.5".
In the case of electronic components, the actual behaviour will be either documented in a datasheet or just common knowledge in the industry. For example if you're buying a standard li-ion battery with no active circuitry, you'll often find the datasheet quite lacking in details because you are expected to just know the characteristics of the li-ion chemistry provided the basic parameters are provided.
This isn’t electronic components, this is sold as a consumer level gadget that anyone can use. No one expects a standard consumer to understand data sheets like that.
You started off by saying you don’t know about the components they’re selling - but that turns out to be absolutely critical to understanding the context here.
Either way, I can’t believe they just let it fry the main board instead of having a sacrificial fuse or equivalent go first in these scenarios, whether it was a product aimed at professionals or not. It’s just dumb.
I don't know how this would be perceived in the US, but in UK/Europe this wouldn't be seen as or regulated as a "consumer level gadget".
It's a main-voltage electrical system. I'm not even sure it would be legal for an electrician without the appropriate qualifications to commercially commission one of these systems. Their website even says installations should be performed by "a licensed electrician or a qualified professional."
In practice, every single solar system I've seen is exactly the same as this one.
A fuse wouldn't help here because they're current protection devices but we're talking about voltages here. Voltages are harder to generically protect against with a sacrificial device, and also over-voltage protection devices themselves have a habit of catching fire even when the voltage is within limits so you probably don't want one right next to your lithium batteries anyway. You'll even find most consumer devices don't have much in the way of continuous overvoltage protection.
It's typical when commissioning solar to just "protect" from panel overvoltage by ensuring your panel outputs are well within the margin of your MPPT (this device appears to be an a combined MPPT, inverter and battery) on a worst case cold day. Really there's just no reason to run your panels right up against the MPPT max voltage.
Given how easy it is to protect against design overvoltage by designing your panel circuits suitably, and how overvoltage protection devices are themselves a point of (potentially catastrophic) failure, I think it's pretty hard to make the case for including one as standard, which is why nobody does.
But leaving this particular issue aside, these devices are totally not suitable for consumer installations unless you like fires.
Maybe it would be a good idea to at least add a pair of MOSFETs (one for each rail, + and -) and a voltage meter? Like, the voltage doesn't rise to maximum instantaneously, there should be ample of time to detect voltage rising to a critical amount.
So say, the input is rated for 150V, spec the components to sustain 180V, and trigger the MOSFETs to disconnect the panels at > 160V.
And maybe also add a big ass buffer capacitor, that can be used to soak up a bit more energy in the case of an inrush spike before the MOSFETs actually disconnect.
MosFET's or IGBTs are likely what failed. And, capacitance is something you do not want on a string of PV.
DC starts getting really nasty to deal with somewhere between 36-52v, with 150v of panels not being something joe-blow should be able to buy on amazon. Designing these systems to be safe is difficult.
> Not everybody buying these has a Ph.D. in physics and if it says 148 V on the label and 150 V on the other label then it's your product that has a problem, not the customer.
Idk. I don't have a PHD, but 220V sounds like 240V to me. I wouldn't do this.
I feel like getting advice about how to wire up electronics should not be so hard.
> Maybe they should just improve their product to make it more resiliant
Adding "resilience" usually adds to the per-unit cost. I think making a web page adds some cost too, but at least that can be amortised.
> And no matter what happens, customer support should help the customer, not blame them.
I think that's happening here: Making a web page to educate future customers seems like a really good idea. I wouldn't have thought that necessary until I saw it, but I'm always excited to learn something new.
The existing customers who did dumb should consider this a relatively cheap education in electronics; cheaper than a PHD at least!
Also, whether the company also gave them rebates or credits we don't know here, but telling "customer support" they "should help the customer" is also telling them they're not helping the customer, and you don't know that.
US appliances using single-phase power work between 208V and 240V so they work on both residential and commercial electrical systems.
Line-to-line voltage on a three-phase 208V system is 208V, line-to-line on 240V single-phase system is 240V.
Most commercial lighting products are rated for 120V-277V so they work on both residential and commercial (480/277V line-to-neutral single phase voltage is 277V)
I have all sorts of electronics that say everything from 208V - 240V that all go in the wall, so I think all those numbers are probably close to each other in whatever a volt is.
I think if I'm worried about a limit of some kind, being within 5% of that limit seems like I might as well be over-limit if the commonly seen distribution I see in my house is greater than 15%
I have a lot of electronics that accept 100-240v doesn’t mean I think they’re close together, just that they have compensating mechanisms to handle such voltages.
The margins are generally lower for higher power devices because the electronics are more expensive. Thankfully these electronics in general are becoming cheaper which is one reason why they’re ending up in the hands of people inexperienced with them.
Also try to tell someone they need an extra 30% in margin and often they'll think they’re being upsold.
> I have a lot of electronics that accept 100-240v doesn’t mean I think they’re close together, just that they have compensating mechanisms to handle such voltages.
I bet you also have a lot of electronics that don't though, and those that do probably say so.
My kitchen mixers, dishwasher, washing machine, driers, rice cooker, refrigerators, sauna, and pool pump aren't that tolerant by a long shot. I've got a few computers with a switch on the back to choose between 220v and 110v.
Plugging something that takes 110v into my house breaks the thing, so I've learned to check.
But I don't have anything that's 208v that can't go into the house. So I think whatever the situation is with volts, within 15% is "basically the same", so coming within 15% of the rated limit, is probably just like exceeding the limit by 15%.
And so this is why I would not expect something at 146V to be under the safety limit of 150V.
> Also try to tell someone they need an extra 30% in margin and often they'll think they’re being upsold.
You’re listing things that are high powered and or old. Modern PSUs don’t have that switch. While it’s in the early stages I expect more white goods to switch to BLDC motors which will likely use voltage transformers that’ll support the 110-240v.
People generally are not lugging white goods internationally, the average persons experience with different voltages is for laptop and phone chargers when they travel.
But for the matter at hand, the margin mentioned is needed on the solar systems, this is where the inverters can get expensive, which is why it can look like an unnecessary upsell to people who’ve never blown a device before.
> You’re listing things that are high powered and or old.
Sure. I have high-powered and old things, and I bet you've seen stuff like that too.
I'm explaining why I, as a non-expert, would not put 146V into something that says it can't take more than 150V.
> People generally are not lugging white goods internationally
Travel doesn't enter into it; My appliances came from Europe, they're just labelled a bunch of different voltages, so I think voltages within that range are roughly equivalent.
Furthermore, British have such a very special relationship with tea, such it would be entirely understandable that a Brit would take their kettle with them and often become quite annoyed that they cannot get an adapter to use it when holidaying amongst the yanks.
At least in parent's case, probably because the vast majority of their comments are black-and-white hot takes that are always downvoted regardless. And they basically never respond when asked for any sources.
They're just being cheap. If you're going to let customers plug panels directly into your box you should have overvoltage protection. It's that simple.
> Making a web page to educate future customers seems like a really good idea
I don't think this is an official website of ecoflow.
Other than that I agree. I don't think asking for a bit of knowledge from the customers is a bad thing. A warning in the manual about safety factors should be enough.
Besides the ratio between the peak and effective value, you must also account for the standard tolerance of the nominal value.
The actual maximum peak voltage for the European mains, is 230 V * 1.15 * sqrt(2), because of a 15% tolerance. That is about 375 V. With a small safety margin, the minimum voltage rating for components connected to 230 V a.k.a. 220 V is of 400 volt.
Makes me wonder if that was how EV DCFC quickly settled with 400VDC. The voltage makes sense if it was somehow known that engineers has intuitions with safe designs for 400Vp-p systems.
So the issue is that 220V is nominal in China, 230V nominal in UE and 240V is UK/part of Australia. So if anyone is preparing product for global market (as most are doing now) more likely then not will support all of this voltages. Thus is kind of normal (but wrong) to assume 220V sounds like 240V.
When the voltage was unified in UE, the nominal value was set to the median of 230 V, but its tolerance was raised from 10% to 15%, so that the new maximum peak value of 230V + 15% will match the old value of 240 V + 10%.
So now for all 220/230/240 V standards you have the same maximum voltage value that is used for electrical designs (about 265 V effective), so they are equivalent, regardless of the name.
True, however there is also old equipment. For example I have heard that light bulbs designed for 220V will last for noticeably shorter period of time ar 230V nominal circuit. That is why it is worth to check supported voltage. But you are right - newer equipment will suport all voltages.
Many charguers are now 100-240V, 50-60Hz, that is close to pluggable anywhere on Earth. (I burned one or two a long time ago, when I forgot to check and used a 120V transformed here with 220V)
Same thing happened to PC PSUs. I don't think there is a recent unit that still has the self-destruct voltage selector switch which pops them if you are in 230V land (and the switch is set to the smaller setting).
Why doesn't this just produce a shutdown? Inverters have to track voltage and current on the input and outputs sides, and can turn themselves off. They shouldn't be that close to the absolute maximum voltage ratings on the components.
Too much current is a heat dissipation problem, and you've got some time to deal with that, at least tens of milliseconds.
Anyone have a teardown on these things? Are they using under-rated MOSFETs? That's all too common in solid state relays from China.
High voltage, low RDSON FETs are (slightly) more expensive, and these products are cheap. A better design would use a higher-voltage rated input switch with poor (slow) switching performance, like an IGBT. Don’t design critical infrastructure around EcoFlow hardware.
Fujitsu, which sells MOSFETs for this application, writes: "Firstly devices should be rated at 600V or 650V, as this will generally provide more than adequate protection against the threat of high voltage transients."[1] That's a nice big safety margin. It should hold until the voltage monitoring shuts the whole thing off.
Not seeing UL certification on this thing.
If we're going to have US protectionism against China, a good first step would be to require UL-type testing, carried out in the US, on all imported electrical devices that run on more than 12VDC or contain a battery chemistry capable of thermal runaway. Electrical safety is a solved problem if you can keep people from cheating.
The voltage ratings of the MOSFETs used for 220/230/240 V applications have been increased over the years.
Decades ago, when bipolar transistors were used, they were rated for 350 V, which is barely enough for 220 V + 10%.
When everybody started to design universal converters usable for 220/230/240 V, the ratings were increased to 400 V. The first power MOSFETs were also rated thus.
Then there were too many converters destroyed by random voltage spikes, so the standard ratings were increased to 500 V. That proved to still be not enough in many places over the world, so the ratings were increased to 600 V or 650 V, already many years ago, in order to make extremely unlikely the destruction of the transistors by voltage spikes much greater than the nominal mains voltage.
600 V or 650 V is used for converter topologies where the transistors see only the peak input voltage. For converter topologies that use fewer transistors, but those see peak-to-peak voltages, the rating of the transistors must be 1200 V.
For 650 V, gallium nitride FETs are the best available devices, while for 1200 V or higher voltages silicon carbide transistors are the best. Silicon transistors are the best only for ratings much lower than 100 V, but they may be preferred also at high voltages for being much cheaper.
My understanding is that mosfets themselves are usually not UL certified/listed. I recently did a UL certification of a power supply and the IGBTs we used were themselves also not UL certified. The UL certification was more about the overall system design.
> They shouldn't be that close to the absolute maximum voltage ratings on the components.
This appears to be a situation where the engineering team determined the absolute maximum input voltage and the marketing/product people put that number straight into the documentation.
Standard practice with electronic parts is to determine the absolute maximum rating, then to specify a recommended maximum that allows for some safety margin and variation.
Instead, this company determined the absolute maximum and then just shipped it.
One way or another, many of us are in agreement the company screwed up and it’s on them to fix it - whether that’s their marketing, their manual, their lack of over voltage protection, whatever it is it’s their fault.
Yet so many people in this thread are so keen to blame the customer, it’s pure ego from them. “I’m too smart for that to happen, so it’s all their fault!” they sneer. Classic bad faith forum behaviour…
That's humanity in general. But yea- general guide says "add up your open circuit voltage and don't exceed that." If something fails because of the panel manages to get more than 1000W of solar flux, and is cold... it's the mfgr's problem.
I need to actually look up why the extra flux increases voltage. Maybe it really doesn't but just moves the MPP to a higher voltage by having more current.
> Plugging in four 400w solar panels in series is similar to filling your gasoline powered car with diesel and wondering why the car manufacturer isn't replacing your new car.
I don’t think this analogy works. The solar input works like Diesel or Gasoline in different temperature. It’s pretty unreasonable to assume the consumer knows when depending on temperature unless the explicitly state in the manual (I’m willing to bet good money majority of the people in US have never read their car manual either)
Around the skiing season, many automotive magazines will remind diesel drivers to buy “winter diesel” or use additives if e.g. driving up to the Alps or similar cold places.
Straight Vegetable Oil (SVO) diesel conversions do. It'll gel at low temperatures, so they blend or switch to a separate tank of regular (or bio) diesel while the engine is cold, wait until it generates enough heat, circulate that heat along the SVO lines and into the tank, then switch over. Then switch back a few minutes before shutdown so the lines are full of regular diesel for the next cold start.
Because they run their engines well within the margins of their design. If you were running at the edge of the envelope you would find that the temperature does matter.
I'm not sure I know what a good analogy looks like. If the two things are identical, then the analogy is uninformative. If they're at all different, you will zero in on the differences rather than the similarities.
Sometimes they can be ok pedagogical tools, but they're easily misused as tools of persuasion.
You’re not supposed to zero in on the ways in which an analogy doesn’t apply. You’re simply supposed to read the analogy in order to see what it’s attempting to _highlight_ about the scenario.
This is a common pet peeve of mine, people not understanding how analogies are supposed to work and getting distracted by the differences. They’re supposed to work like a light filter placed over a lens, something will be highlighted and focus on that, don’t focus on the fact that “but all the colours are different now!”, the only purpose of using the light filter was to highlight a specific part of the image, the fact that it also coloured everything wrong temporarily is supposed to be ignored.
You know, just to use an analogy to explain analogies. Gotta be as meta as possible.
I was going to comment on the manufacturer's safety margins, but then I found a graph [1] on the variability of voltage vs temperature and it seems to be a lot steeper than I thought/expected, to the point that I'm wondering how these do not require either training or a voltage regulator to install and operate properly:
Basically anything that consumes solar power incorporates what's called a "MPPT", or maximum power point tracker.
Basically, it's a smart DC-DC converter that continually tracks the voltage/current output of a solar panel and adjusts the load to extract the maximum available power from the panel.
It's not uncommon to have issues with extremely high panel voltages in snowy climates, when they're first illuminated in the morning. If you are close to the maximum voltage your MPPT charger can handle in normal circumstances, extreme cold can even damage things during the initial morning transient. You then have to do oddball things like use a crowbar system to prevent blowing up your MPPT system.
Another post commented but that’s exactly the point of the MPPT. Not only is it temperature dependent but solar incidence angle matters too (how the sun angle is relative to the surface). MPPT works by changing the internal impedance to match the ideal charging voltage. But there’s a limit to how much it can regulate but I think it’s very fair that a consumer would expect nominal voltage times panels in series is less than the marketed solar input to work.
There's a reason people don't install electric equipment without training.
This is just like not upsizing wire gauge if you have a bunch that are loaded simultaneously buried together in a somewhat insulating wall.
Without the burying under plaster, everything would be fine.
But combine that with simultaneous loading during summer, and you fry/roast the PVC insulation.
> There's a reason people don't install electric equipment without training.
I’m not sure if I follow that logic and if your analogy follows. I would argue this is closer plugging in an appliance rather than running wires. If I run a 15A appliance on a 10A breaker, a normal person without training would expect the breaker to trip. This is like running a 10A appliance and the 15A breaker trips because the appliance is sometimes 16A when it works in the cold.
> If I run a 15A appliance on a 10A breaker, a normal person without training would expect the breaker to trip.
Would the breaker trip in this case? I thought in this case it'd be more likely to start a fire.
Edit: thinking about this more, I think I'm wrong. A fire would start if your wires were too thin for a given amperage. Breakers detect current flowing.
The part that they are warning about burning out is a voltage regulator.
Those things are normally built to handle a nominal 115 V assembly of panels. There's probably something on the manual about this, but when you put a giant label saying your device supports 150V, people are not going to read the manual.
Sounds to me like someone is misrepresenting their products. A solar panel's VoC should be its maximum possible output in ideal conditions (open circuit). If that's under your product's maximum input voltage, it should be no problem. Ever.
Is EcoFlow advertising a higher input voltage than their products can actually take, assuming most people won't actually reach it due to temperature inefficiencies? That'd be false marketing, and it'd make this article manipulative, false blaming of the customer.
STC ("standard testing conditions" for solar panels) is 25C so if it's freezing 0C you have 25 multiplied by 0.33 Volt = 8.25 Volt more than STC in open circuit situation.
Unfortunately inverter manufacturers seldom document how many Volt will destroy the MPPT and up to how many Volt the MPPT will safely turn off by itself before breaking.
Not to mention a fail-safe MPPT would/should just crowbar the input if there's any potential for overvoltage.
Solar panels are current sources that waste their power into a long string of silicon PIN diodes that eventually reach their forward voltage and begin to eat up all that juicy current.
You can just take the current and keep the voltage as low as you want, just make sure to take all the current or it's voltage will rise to let the diodes take the current you aren't using.
> A solar panel's VoC should be its maximum possible output in ideal conditions (open circuit)
I think this is where the confusion arises - what do you mean by ideal conditions? Ideal conditions for solar generation are not necessarily at the same time as the highest voltage operating conditions. VoC tends to be specified at Standard Test Conditions which has light-levels representative of a sunny day (1000 W/m2) and a cell temperature (not ambient) of 25 degrees C, which is already a lot cooler than most panels would typically be at that level of irradiance. So really, the label is already specifying a voltage higher than what you would typically experience during times of max generation.
However, the max voltage could exceed this rating at times when there are cold ambient temperatures with enough light for the module to function, but not enough sun to meaningfully heat the cells. So in this scenario you may have maximum voltage, but you're far from maximum power nor at 'ideal conditions'.
What does “maximum possible voltage” mean for a solar panel? Do you include things like cloud edge effect (which increases incident light beyond direct sunlight?) What about installs with a nearby window reflecting light onto the panel? Do you include ultra-cold environments (which will reduce the resistance and therefore often increase voltage, although admittedly not, I think, Voc)?
VoC is the maximum potential voltage a cell is physically capable of producing. It does not consider real-world conditions. Rather, real-world conditions cause the solar panel's output voltage to be somewhere between 0 and its VoC.
Voc is just the open circuit voltage measured at the terminals (plugs). “Nameplate” Voc is at standard test conditions (STC) of 1000 W/m^2, 25 deg C cell temperature, and a standard are mass/spectrum. The combo of 1000 W/m^2 and 25 C cell temp is not common in the real world in most climates, but still happens. Even relatively hot climates can have times in winter that exceed nameplate Voc if inverters turn off (making the panels go to open circuit).
Obviously you include everything, otherwise it wouldn't be a maximum. You can define a minimum temperature for this, of course, but the customer should know about it.
There's no theoretical maximum voltages for solar panels like there kind of is for batteries. They're just giant array of photodiodes and they just generate whatever voltage potentials proportionate to amount of lights received.
You could produce a "max voltage flying low earth orbit over Gobi with no shadows from Starlinks" value, but that's just the value for circumstantial most absurd situation you happened to have come up with, not a guaranteed theoretical maximum.
The current is what varies proportionally with the amount of light received.
The open-circuit voltage depends mostly on the structure of the solar cells and on the temperature. It has only a very weak (logarithmic) dependence on the amount of light received.
The voltage that you measure at the output depends on the open-circuit voltage, on the amount of light received and on the amount of current that you draw from the panel.
The maximum open circuit voltage for a solar cell is easy to estimate, because it happens at the minimum temperature for which it is designed and the maximum solar illumination. It can be exceeded only using a light concentrator that projects on the panel light collected from a much greater area.
There is a theoretical maximum: the open circuit voltage of a single photovoltaic junction cannot exceed the bandgap of the semiconductor used, no matter how much light you apply. The manufacturer knows the semiconductor used and the number of junctions in series.
They produce current until the diodes start conducting given the forward voltage, as they'll take any current you don't extract off of your hands.
Of course if you want to extract maximum power you have to balance the higher worth of the current you take against the loss of current to the diode forward conduction.
Why does the Delta Pro not have a fuse on the input, with the MPPT limiting the max voltage to 150v (by upping the current until the voltage sags and/or the fuse blows, or even a straight crowbar circuit). This is a premium consumer brand selling a mostly complete product, and protecting the input from overvoltage would be straightforward. The frustration at the warranty weaseling isn't surprising.
You might think that the voltage rise could be too fast for most protective technologies to save the downstream electronics, but the general case is that the temperature slowly drops and the sun slowly rises. So the voltage should slowly approach the limit.
Adding a normally-open relay and a voltmeter and a microcontroller should fix this. Relay won't close on startup unless the voltage is safe. Microcontroller will open the relay if the voltage gradually nears the limit. Should be solvable for <$5 in parts.
Dark start (when the batteries are flat w/o grid power) will be challenging. There will need to be a small battery to power the voltmeter and relay, or a high-voltage tolerant supply to power the microcontroller and relay temporarily. A 9V should likely be sufficient.
Common relays don't handle 150VDC, and I'd spec the voltage even higher even though one would think the voltage rating has more to do with arc interruption rather than creepage while off. Also a microcontroller is complete overkill, draws too much current to be easily powerable by the solar panel side, and adds complexity for something to go wrong. A simple analog comparator suffices.
The standard answer for overvoltage protection is a crowbar circuit + fuse, and I think that's what I'd aim for rather than a relay. The problem with DIYing that is knowing the input capacitance of the Delta and finding out whether it has any other problems with its input being abruptly shorted.
No the DC/DC converter could just turn it's transistors to short out the panels and rely on the fuse you want anyways to handle idiots paralleling more panels than allowed.
Why isn't there code/regulations for tbis. Why do you need blog advice.
It is like using too thin wiring to your oven or something. Because you based it off how you typically use the oven not is max draw plus decent margin.
Which is why you get a qualified electrician who knows or get qualified yourself.
> Why isn't there code/regulations for tbis. Why do you need blog advice.
On pretty much every other device (domestic for sure, I don't actually know abount commercial) there is.
> It is like using too thin wiring to your oven or something. Because you based it off how you typically use the oven not is max draw plus decent margin.
Sure, but with all other electrical labelling the numbers are correct. Imagine if Neff said "you only need an 13A rated socket" for their oven, and then when you want to bake bread it draws more. That's very different to Neff saying "you need 45A", and deciding to install it on a 13A socket yourself because you don't need to make bread. The former is what's happening in this case.
Most household solar systems do require permitting and inspections before you can turn it on. There are some exceptions in a few states for very small systems now. Ecoflow provides equipment for these small legal unpermitted installs.
More importantly, equipment shouldn’t self destruct in a dangerous fashion when pushed over the limit.
A lot of people here are saying things are mislabeled, but every single solar panel comes with a datasheet that shows its Voc and temperature coefficient.
Solar panel manufactures can’t give you a hard maximum on voltage because temperature will make that vary. Anyone who is buying solar panels without understanding the temperature coefficient shouldn’t be buying solar panels. It’s not hard to understand and there are hundreds of guides out there explaining it if you just search for terms on the datasheet.
When I got solar panels for my (former) house 15 years ago, as I recall, the best practice was to have panels in parallel (each with its own microinverter) and not in serial as serial would cause loss of efficiency when there was partial blockage of panels. (I could be misremembering all of this).
That's only relevant if you're so starved for panel area that you can't put them into places that have each sub array sufficiently homogeneous and only partially shaded during sunrise/sunset.
I’ve never heard it called magic smoke before, but a regular saying at one of my old jobs was “ah yeah we let the smoke out” in relation to 100% electric drive vehicles. Smoked many inverters, shorted 96v bus to a 24v bus, etc.
It was almost a rite of passage to “let the smoke out” in that org. That job was actually great because as a software engineer I happily spent a lot of time with a fluke, a wrench, arm buried in the bowels of a vehicle fishing out sockets, etc. Writing the software was not the hardest part of those programs, but being one of the handful of folks that knew the entire electrical, cooling, mechanical, and software systems made us the most valuable folks on the program. We had to know all those things in order to write the software correctly.
What we’re seeing here is the mismatch between component level specs and end user ratings. A device which is rated to 24V input power will probably tolerate up to 32V and it surviving 60V would not be uncommon. A component with a Vmax of 24V probably explodes if it sees 25V.
Calculating temperature correction is in both the NEC and CEC. Here's the CEC version:
64-202 Voltage of solar photovoltaic systems (see Appendix B)
1) The maximum photovoltaic source and output circuit voltage shall be the rated open-circuit voltage of the photovoltaic power source multiplied by 125%.
2) Notwithstanding Subrule 1), the maximum photovoltaic source and output circuit voltage shall be permitted to be calculated using
a) the rated open-circuit voltage of the photovoltaic power source;
b) the difference between 25 °C and the lowest expected daily minimum temperature; and
c) the voltage temperature coefficient as specified by the manufacturer.
This is not a problem in a properly dimensioned system at all.
It is still well within the 'engineering reserve'. Solar panels produce the most power in mid March, when they are cooled very well by the ambient air but the sun is already lining up nicely with the panels at mid-day. But those conditions are pretty rare, and most inverters will handle this gracefully by simply dumping some of the excess power as heat - or in the better ones, by simply chopping the input voltage at a high frequency. This allows for very fine control over the average power and will help to keep the voltage under the isolation break down voltage (which usually is a very large factor over the voltages that you see in practice).
My own system is 50 panels, 1000V maximum on panels that nominally produce up to 100V, so I never have more than 8 of them in series. That leaves 200V to play with and I've never seen it get close to that 1000V. The inverters are easily capable of dealing with this and if the strings were to ever exceed 1000V then the inverters would simply disconnect those strings with their internal disconnect relays.
So, in closing: don't run your system 'on the limit' or rare conditions will push it over the limit. But even if you do: inverters are fairly bullet proof nowadays and if you over-volt the input the vast majority of the ones that you can normally buy are going to just switch off and move to an error state that will require you to power them down before they will be usable again.
Where to start, eh!
So most everything to do with off grid specifications can be listed as "nominal", ish, depending on, etc.Not knowing this means that persistance will provide the circumstance to be educated.
There are a number of ways to get things wrong and melt stuff, or get hurt.
Batteries should always be treated as unpredictable dangerous beasts, happy as a clam if they are treated just right, but capable of producing trouble and disaster, or just del8vering a viscious bite to the unsuspecting and surviving to do it again. A 48volt (nominal) battery bank will happily turn the required 10mm wrench into single demonstration of a wide range of metelurgical and other phenomina.
For fun on a cold morning take the leads from a 3 kw solar array, off, and then strike the wires to produce a realy big fat arc, h3y hey!
The simple fact, that I tell enthused,nice, but clearly unprepared people who express interest in "off grid", is that I do it, but it's not for everybody, as there is a significant technical learning curve, plus the required physical skills to mount panels, run wireing, deal with battery banks,set up the systems, and if costs are to be kept to a minimum then source parts from distributors or import directly.
I can imagine future solar panels sending spec data to the MPPT using Power Line Communication (PLC), allowing the system to shut itself down gracefully rather than dying. Rapid-shutdown systems already send keepalives using PLC today.
But then it goes all Black Mirror, with manufacturers restricting solar-panel operation to approved devices only, and UIDs being used to enhance shareholder value through recurring subscription revenue.
The MPPT could just short them out and it'd be fine; solar panels are a current source with a huge string of non-light-emitting diodes wired in parallel with the output happy to soak up any excess current around their forward voltage.
(Technically the current source in question is _within_ the diode's junction capacitance.)
Today's inverters have a volt limit and an amp limit and you must stay within both.
But physics doesn't require that - you could instead design a solar inverter where you could stay within either!
It would work by detecting when one limit (volts or amps) was about to be exceeded, and pushing the operational point away from there. Remember that for solar there are two zero power - ie safe - points. I=0 is the usual one, but V=0 (ie short circuit) is equally safe for solar panels.
So this hypothetical inverter would operate between one of the safe points and the max power point.
Obviously whilst installing the system and humans unplugging wires, the V=0, huge current safe point is impractical. But that's why you have breakers.
Worth noting that the physics of electricity has an odd symmetry between voltage, power and current which means almost any circuit can be redesigned to effectively switch around all V's and I's and still work.
It is mere convention that we have decided that V should usually be regulated and constant and a property of the supply whilst I is variable and determined by the load.
The cause of this problem is the standards for Solar Panels, that has the outputs measured at 25C so they are comparable with each other. The specification sheets for panels do list their peak voltage in other conditions but all the advertising is based on the standard. Solar installers know about this and size accordingly but your average consumer doesn't and is very quickly going to get into trouble with this.
I think what Delta needs to do here is accept that the standards mean all Solar will be sold this way and appropriately oversize the inverter so that it can cope with -10C sunny days. Yes its annoying for them but the reality is devices sold to people who don't know how all this works need to compensate for lack of expert knowledge in its user base.
I never tried the solar charging on my ecoflow so this fragility surprises me a bit.
I've been able to run laundry in a machine with a 1/2hp motor using the inverter side on multiple occasions. No smoke or funny smells. My 2200w generator would trip out the instant the spin cycle tried to start.
The solar panel with inverter does not have any inertia so it can survive power spikes more easily, can lower the voltage till it's over. The generator on the other hand has physical rotating parts that could be damaged by sudden torque asked by increased load. Of course it could be mitigated with additional "soft start" circuitry on the motor but that's usually not included. Not capacitor alone please, you risk more damage.
Slightly OT, but how big of a capacitor would be needed to smooth out those current spikes? Solar-friendly could be a selling point for some appliances.
I wonder if such a capacitor could even be retrofitted.
A capacitor wouldn't help in this case. They're most useful when you need to overcome transient situations like a locked rotor, not when you have a heavy drum that needs to be spun up from zero. During this phase the machine can consume well over 2kW of power for a few seconds. The circuit is rated for continuous 15A, but it has no problem supplying 20 or 25 for a brief period of time.
It would help at noon, when usually inverters make so much power they push the local grid to saturation which causes them to disconnect from the grid for a while. There are different rules for this for different localities, typically the installer will pick the regime appropriate for the local grid. Where I live (NL) the voltage is allowed to hit 253V for up to a minute, if it takes longer than that my inverters will switch off. That's a requirement to pass inspection, if your inverter can not do this then that's an automatic fail.
There are 'home batteries' that store power for practical reasons up to a day, maybe two. They are useful for sunny/cloudy conditions to maximize the amount of power locally consumed. But battery storage and retrieval isn't free and so far - at least, for my installation - this does not make economic sense. But another factor of two in price drop for my preferred chemistry and it definitely would make sense and then I would probably install about 20KWh worth of capacity. The trick then becomes to balance power sent to the grid and sent to the battery so that you maximize the utility of the grid in order not to wear out the battery prematurely. That means cycling the battery between 70 and 90% state-of-charge for Lithium-Ion. I'd much rather have Lithium Titanate so that is what I'll be holding out for, they are already available, but still too expensive. But they're much safer and have far better charge/discharge curves and life-span.
I actually meant a small li-ion inside the appliance, to smooth out the load. Do any batteries support 20C or 30C? That seems like enough to smooth such a load.
The problem would not even be making it initially, the problem would be to keep it safe in the long run. I am not a huge fan of all these embedded Lithium-Ion batteries, they're flooding the market (and our homes) and they are disproportionally large factor in house fires.
Don't bother; at that point just plug them into 200~300 V DC right to the battery (with just fuse and meter between, no need for any conversion, the washer motor controller that'd be needed to utilize a capacitor for smoothing these spikes would do just fine on a reasonable battery charge/discharge voltage spread.
A few years ago, I plugged a single 100W solar panel into a battery pack that advertised it accepts 18 volts. I left it plugged in, on my deck, for hours. When I came back, there was a foul smell and some parts of the battery pack had turned black, apparently from getting charred. The battery pack no longer worked at all. I was very fortunate that only the control circuit had been destroyed and the battery cells (and my deck) had not been touched.
Lesson learned: don't skimp on Li-ion battery packs!
Also, I have a question about this article. Don't EcoFlow battery packs have a circuit that checks the incoming voltage and automatically shuts off charging if the voltage is too high? I would also expect a loud alert.
Can anyone comment on the "You can exceed the amperage specs" ? I made myself a little case study using 4x1W panels and using them in series and parallel. I got the distinct impression that running panels in parallel is better in not so bright conditions compared to a single panel. Whereas a serial configuration made it worse. Since the sun doesn't shine here that much. Running in parallel seems to be preferable, but it would slightly exceed the amperage spec of a few converter i sampled.
It be worth looking up the I-V curves of solar modules on a datasheet - a key factor is that the maximum power point of a solar module (for a given set of environmental conditions) is really dependent on the voltage that it is running at (whereas the current is more constant based on the light level, up to a certain voltage), so to get the maximum power out the resistance of the load needs to be matched to achieve that maximum power voltage (V_MP).
This is what MPPT controllers do, as this maximum power setpoint will change as environmental conditions change.
The problem is usually shading, not so much the capacity of the wiring, though, if you try hard enough you can exceed the rating of the final stretch of wiring to the inverter (or the little pigtail in the inverter if you connect all of the strings at max voltage/amperage). Shading can really upset the current flow in a set of parallel/series connected panels and can cause local hotspots due to overcurrent. Usually inverters are pretty smart about this and they'll detect that you are pushing it further than is responsible and they will just switch off. I've purposefully triggered such conditions to ensure my installation is safe and I was pretty impressed with how utterly painless fault detection, isolation and recovery are in modern inverters. I also had an older one and there it definitely wasn't all that friendly, to the point that the whole thing had to be hard disconnected from the grid before it would work again.
>Plugging in four 400w solar panels in series is similar to filling your gasoline powered car with diesel and wondering why the car manufacturer isn't replacing your new car.
Ok, that is a very bad answer. Diesel fuel contains more amounts of energy per drop as gasoline, but that doesn't mean engine damage will result. Diesel fuel will not damage an engine if you were stupid enough to get it wrong at the pump. It will simply refuse to cycle until the diesel fuel is pumped out and the correct fuel is pumped in.
Maybe it’s different in the rest of the world (I doubt it), but the fuel nozzles for gasoline and diesel are different. You can’t put a diesel nozzle into the opening on a gasoline car, so it’s rather difficult to fill a gasoline car with diesel fuel.
The other way around is possible. You can fill a diesel tank with gasoline. Whether it destroys the engine or not depends on how much gasoline you put in. A gallon or two that is then diluted by filling the rest of the tank with diesel is not likely to cause any lasting damage. If you fill a tank 3/4 of the way with gasoline and try running it in a diesel you are probably going to need a new engine.
So yeah, the analogy is not good. Slightly exceeding the rated voltage and breaking the whole thing is usually not the same as putting a little gasoline in your diesel tank.
I am surprised that open circuit voltage is specified at 25°C and increases dramatically as the temperature goes down. Seems backwards! I'm looking at the Ecoflow spec sheet right now and fair enough, it's got the open circuit voltage and then the Temperature Coefficient of Open Circuit Voltage (-0.35%/°C) right next to it.
Great, guys, how about you go ahead and multiply those two numbers for me, since you're the ones writing the fucking spec sheet? It's like if car battery manufacturers only specified a cranking amps number, and told you to figure out cold cranking amps yourself.
> how about you go ahead and multiply those two numbers for me
What are you going to fill in for the third number, though? With an open-circuit voltage of 37.10V at 25°C and a coefficient of -0.35%/°C it can theoretically go up to 75V at absolute zero. And that open-circuit voltage is with an irradiance of 1000 W/m2, should we also account for the possibility of someone building a heliostat around it?
There's no one-size-fits-all number they could possibly quote. It'll always depend on the environment, because that's just how the physics work. The best you can do is provide a figure for the standardized testing environment and the relevant coefficients - which is exactly what they are doing.
At merely freezing, that solar panel would hit 40 volts. In the coldest point of the US in a typical winter, it would get up to about 42 volts. At the record minimum temperature, in either montana or alaska since they have similar records, you'd get up to about 48 volts.
42-48 is not a big enough range to give up over. My impulse is to arbitrarily pick -40 and say the normal max voltage is 45.5 degrees. Now it's nice and obvious that you can only hook up 3 to a 150 volt input, and you'll have a 9% margin of error left over. On that "first cold and sunny day" you'll output 120 volts instead of 160.
A solar panel is like a normal silicon diode. The voltage over the cell goes up drastically with lower temperatures. In cold climates crowbars are usually added.
Our installation from 2017 of 40 panels work great here in the middle of Sweden.
Covered in snow over the winter and generate little power November-February but rest of the year we have fine power output, with peaks May-July (obviously).
It’s not that it lowers the maximum voltage that the charge controller/inverter can handle. It’s actually that the panels become MORE efficient in the cold temperatures, resulting in a (potentially unconsidered by end-user) increase in voltage, overwhelming the downstream BoS components.
Solar panel voltage goes up as temperature decreases. The chart is misleading, it's stating something like an equivalent max voltage if you think of the solar cell voltage as staying the same (and presuming your temperature coefficient matches)
I think it works this way but I could be wrong:
1. The forward voltage across a diode depends on the current, and the graph is r-shaped. For a certain diode, 0.01A might make the voltage across it 0.4V, 0.1A might be 0.6V, 1A might be 0.65V.
2. The forward voltage also depends on the temperature of the diode. For a certain diode, per °C decrease there could be a 0.002V increase.
Let's say with certain current there is 0.687V. If two diodes are connected in series i.e. (point a) → diode 1 → diode 2 → (point b), and each has a 0.687V voltage across, that's 0.687 + 0.687 = 1.374 V between point b and point a.
For the solar diodes, the "current" depends on how "strong" the sun is. If at a certain "current", across each diode is 0.687V, you'll need 216 diodes in series (between two points) to get 0.687×216≈148.4 V.
If there is 0.002 V increase per diode per 1°C decrease, with 216 diodes, that's a 0.002×216=0.432V increase per °C decrease, so with a 4°C decrease it exceeds the MPPT's limit.
Another thing about solar that differs from how diodes are "normally" used in circuits is that the "true" voltage depends on the max current achievable with the how bright the sun is right now, instead of the "true" current. When the "true" current is 0 A, the voltage across each diode might be 0.687 V. When the "true" current is 0.5 A, maybe 0.65 V. 1A, maybe 0.6V. 2A, maybe 0.3V. Try to get more "true" current, the "true" voltage drops. Try to get more "true" voltage, the "true" current drops. Power is voltage × current so when full speed charging, the MPPT uses an algorithm to find the (possibly) best minimum (not maximum) input voltage based on the temperature etc and trades voltage for current at the output. If there is no minimum input voltage restriction, solar will follow the battery's terminal voltage + cable drop instead, and instead of something like 111V, there could for example be a ~4x less powerful 25.5V (if the battery is a "24 V") with just 10% more current.
At the MPPTed min input voltage for full speed charging, maybe 111V, all might seem well even with low temperatures, but when the battery is full and there is approximately nothing using electricity from solar, the real input current will be ~0 A, so there will no voltage "sag", so the solar will realize the full voltage corresponding to the temperature and the illumination, potentially >150 V...
Lower temperatures increase PV max voltage output, not lower it. Conversely, when solar panel temperature increases, voltage decreases. So the headline specs/outputs assume to be valid at a particular temperature. As the temperature of the panels change, the realized performance changes.
Last year, I did yet another PV install at a friends house. While plugging the SMA inverter to the solar field (600V), I fucked up and inverted plus & minus.
Nothing happened. I read the manual and realised that SMA inverters are protected against reverse polarity. Yeah, a bit more expensive, but well worth it
I'm more surprised you managed to plug them in reversed; did you have good reason to avoid the polarized semi-pwrmanently-latching connects that most panels ship with?
Because panels are on the roof, the inverter is on the basement, so you have to run your own cables and crimp the mc4 connectors on them. If you swap them around they get mixed up ;-)
This is what happens when something goes mainstream. The background knowledge that "everybody knows" when it's niche, because only turbo-nerds are into it, simply isn't common sense for everybody in the wider population.
Back when Home Power magazine started up, the panels were super expensive, and squeezing out every watt was important. Since high temperatures decrease voltage and output, keeping the panels cool (while baking in the sun!) was top-of-mind for every installation. And right along with learning that critical consideration, everyone also learned the caveat that in the bitter cold, that very same phenomenon means they can produce significantly more. Temperature coefficient was simply something "everyone knew".
Now they're so cheap nobody cares. The magazine shut down because "alternative power" and EVs aren't exactly alternative anymore, you can buy one off the dealer's lot, it's nuts. And the panels are crazy cheap now. If you lose 10% because the panels are hot, it's likely cheaper to just buy 10% more panels, than to redesign your support brackets to allow better airflow. But nobody highlights the phenomenon behind the efficiency loss.
"Everybody knew" that the ratings on the panel are at Standard Test Conditions: 25°C and 1000W/m². That's almost never the conditions in the real world, but it establishes a legal baseline whereby panels can be compared apples-to-apples and advertising kept honest (if anyone cared), but deviate from STC and output will go down, or up. Again, ask today's consumer what the ratings on the label mean, and most of 'em have never heard of STC nor could define how the nameplate wattage is just one point on a curve.
Is this the panel manufacturer's fault? They're labeling things precisely the same as they've labeled them for 40-plus years. (Perhaps there's even more data on the panel label now, as Vmp and Imp are typically specified now, and they weren't always universal.)
Edit to add: The label doesn't typically specify the temperature coefficient, but for every panel I've checked, it is in the datasheet. But who reads datasheets?
Is it the inverter manufacturer's fault? They're labeling things precisely the same as they've labeled them for 40-plus years. The input max is a hard limit where the silicon can take no more, and there's a certain amount of headroom required between that and the panels' max, after compensating for temperature coefficient. Of course you calculate your panel voltage for your local conditions before comparing it to the inverter input, duh!
The input max is for most inverters on the market now a setpoint where they will simply disconnect, stop generating power and go into an error state that you need to hard-reset if you want to use the inverter again. It's pretty typical to have a 1000V hard limit on a nominally 800V or 600V system. If you're going to ride close to the limit then on some days you will see overvoltage and disconnects. So it is something you simply should not do. But people think that if the label says 1000V then 990V total nominal panel voltage should be fine, which it obviously is not. Panels are analog devices, they will produce an open circuit voltage much higher than their nominal use voltage and when you're on a switched mode inverter that means that the average voltage may well be 'in spec' but the voltage from one millisecond to another may well be outside of that if the system was built 'on the edge'. And because inverters have to take the grid side into account as well (they are not allowed to exceed certain voltages) there is always the risk of not being able to load the panels sufficiently to get the voltage to drop. So you should side your system so that the open loop voltage of your panels under ideal conditions is still comfortably lower than the max input voltage of the inverter. 800V nominal is pretty close to that limit, 700 is better and 600 is playing it safe.
I think one of the main reasons why installers tend to overprovision voltage wise is that they count on the inverters switching off the whole string every now and then versus being able to make more power without a lot of additional wiring under normal conditions. The net effect of that is positive.
Low quality inverters (the ones without the ability to disconnect the HV side autonomously) should be avoided like the plague anyway, those are simply unsafe and as far as I am concerned should not be allowed for re-sale at all.
My own system can make 17KW on a very good day in March at 1 pm or so, but normally it is closer to 12KW even in the summer. So those peaks are actually substantially over the normal output. Over a given day the average is about 5 KW or so from sunrise to sundown, and those first and last hours hardly contribute.
The subtitle is, though, and I do find a problem with it. There might be someone out there (possibly not sober) who thinks "Magic smoke? Let's see some!" It also somewhat distorts the original. It should be more like "unless you want the magic smoke to escape." The smoke's magic properties are gone once that happens. At least, nobody has ever proven the escapee smoke has any.
Maybe they should just improve their product to make it more resiliant, rather than blaming customers for thinking that 148 V is below 150 V? Not everybody buying these has a Ph.D. in physics and if it says 148 V on the label and 150 V on the other label then it's your product that has a problem, not the customer.
And no matter what happens, customer support should help the customer, not blame them.
This is 100% on the manufacturer if they intentionally chose to highlight the "best case" 150V, rather than the 120V lower end. Especially without any additional safety mechanisms.
The article presents it oddly, it's not that the converter maximum input gets lower, it's the solar panel output that gets higher from the nominal quoted value (which is not a maximum, and not really intended to be used as such). Derating your converter is equivalent for the purposes of ensuring margins, but it implies the issue is in the wrong place.
The idea of safety margins has died under the more pressing type - profit margins.
The failsafe circuit to protect against this (over voltage condition) is maybe $3 and incredibly routine in anything with power. I would bet everything that it is in there.
What's most likely though is that the fuse is also internal, and externally the unit will appear bricked.
While in general most parts will work beyond their ratings to at least some degree, this isn't really a safety margin. A safety margin is known, rated, and validated, and usually a property of a system as opposed to just one part within it.
That’s what I said?
Usually a system would have a safety margin of at least 1.5x, or 3x or the like.
In this case the design safety margin appears to be…. 1x? Exactly?
Suspiciously so. I'd love to see somebody(or somebodies) with an established reputation reverse the controller software & hardware.
Your safety margin is my profit margin.
- Mr MBA
Your converter doesn't need to like the voltage, it just can't break from it. In fact, if it's the type that shorts the panels for curtailing, it should be happy to just run them at the highest voltage it's comfortable with, loosing a few percent generation during exceptionally cold days.
> it just can't break from it
In fact, they can.
I think they meant “it just can’t” in the sense of “it shouldn’t under any circumstances”
Even that interpretation would be be wrong because it can and it does and the circumstances are very clearly described. Every inverter worth considering for a home installation has this capability. Only really old ones are not able to disconnect from the HV side when things are about to go pear shaped. If I had an inverter without that capability I'd get rid of it immediately because that's an accident waiting to happen.
Open circuit voltage is _very much_ widely considered to be the maximum. If its not spec'd openly as " at temp X" then it's reasonable to expect it to be invariant.
"Voc 37v @ 25*C"
Vs
"Voc 37v"
Edit: Isc is the same- max current.
But that's not true - V_OC for PV modules is nearly always spec'd at STC or NOCT, which is clearly stated on module datasheets along with the temperature coefficient of that voltage.
E.g. choosing a random Jinko datasheet: https://jinkosolarcdn.shwebspace.com/uploads/JKM600-625N-66H...
V_OC is specified at both STC and NOTC, and the datasheet clearly states which environmental conditions accounted for in those test conditions.
It doesn't matter if it's true. And those spec sheets aren't what you'll find on amazon products. I looked at them, didn't see any mention of temperature. Also, stupid things use XT60 connectors. Not remotely appropriate for 150v DC.
I read it as a problem with solar panel voltage going over declared threshold of 37v in certain meteo conditions.
That is the issue is with the wrong labeling of things that are being plugged into this vendor's device, not the vendor's own labeling.
I believe the vendor here produces both the device and the panels being plugged into it, and while they also supply other vendors' panels, they seem concerned primarily with customers who buy all components from them and then experience this failure.
I agree the labeling is an issue here, but the solution must come from the wider industry or regulatory bodies; the alternative is for vendors to switch to their own pseudo-units to internalize the math, which would not be good for customers either - think "ACME Generator2000 accepts up to 4 Power Units of input; each ACME SuperEco Panel supplies 1 Power Unit, or 1.5 Power Units if you're in Canada...".
Saving users from having to do a little thinking to not brick their device is a tried-and-true excuse for vendor lock-in in our industry :).
Why not label the panel with the maximum possible voltage that it can produce? Or even have a little table showing the maximum possible voltage at various ambient temperatures. It's not as if there isn't room on the back of the panel for a big enough label.
This is information is generally stated on the module datasheets, which specify the Open Circuit Voltage (V_OC) at Standard Test Conditions (STC), and then provide a temperature coefficient for how that voltage changes with temperature. 'Maximum voltage' is very arbitrary as this is directly dependant on the lowest expected operating temperature, hence the industry has landed on stating these values at standardized conditions (STC and NOCT) allowing for direct comparison.
The label on the modules themselves tend to also provide these ratings at STC, e.g. this label from Jinko specifies the Open circuit voltage and also summarizes the conditions assumed for STC:
https://image.made-in-china.com/202f0j00LURcYuatWIqH/Jinko-M...
While I agree that the label could also add the temperature coefficient, I'm not sure if it's reasonable to expect that specialist electrical equipment details all of its operating parameters on an attached label without the expectation of consulting a datasheet or manual. For specific products that primarily target non-specialised consumers however, a different labelling approach may be warranted.
The entire industry has standardized in having "typical" and "maximum" values decades ago. That problem there is completely self-imposed.
The flip side of this is also dumb labelling. ‘Product may contain traces of nuts’.
Completely unhelpful to those that need the info.
That is in fact useful information to someone that needs that info, because it means they should never eat it. I think this is a bad example, because I have no idea what you're talking about.
Likely a reference to the recent addition of sesame to the allergen disclosure legislation in the US, and the subsequent rampant over labeling.
Nobody seems to remember a bunch of companies receiving rather large fines for pulling known bull-crap "may contain sesame."
If something can go wrong, it will go wrong. So both parties should note that something can go wrong and point to that something.
In both examples given you can have 2 panels in series.
So given that in almost all use cases, you can have 2 panels in series, they should just say “max 2 panels in series”. Simple.
A good product hides complexity from the user with sane defaults and optional advanced configuration. This feels like the same problem.
Panels are not standardized and are themselves series-parallel constructions with wildly diverse specs.
There's hiding complexity, and then there's creating fake reality for people.
As it is, panels are gonna produce variable power depending on the weather. Putting interoperability with third-party panels aside, to get the simplicity of "max 2 panels in series", they'd have to either cap the max power on the panel/generator link and dump the excess, or set the limit based on the worst case a customer is likely to encounter. I.e. they're either gonna waste power, or gouge their customers for extra hardware. Neither of that makes sense for an ecological product sold to a price-conscious customer base :).
The problem is that you run higher voltages with the same hardware if your in Alaska than if you're in Florida. Substantially so.
"Wasting" those 5~10% during severe winter conditions isn't worth splurging on the voltage converter.
Though then selling units that suggest to not run a few hundred volt strings before paralleling instead does sound bad, as the string doesn't need separate fuses rated to many volts DC.
> make it more resiliant, rather than blaming customers
Yeah, this sounds very much like "you're holding it wrong".
They can add a relay, I guess? Voltage monitoring is cheap. Relays might push price above a bit, but it's a worthy premium to pay in my book.
Considering the electric code has an 80% rule for loads, anyone assuming they can use 100% of what is on a label probably should not be doing electrical work.
Which electrical code? They vary from country to country and even state/province in some countries!
I agree with you, but. The NEC has an 80% rule for continuous loads (over 3 hours) that use a typical circuit breaker as overcurrent protection. If you use fuses or a 100% rated breaker as your over current protection, then you can use all of the available ampacity. Anyways, devices that use a 15A receptacle (for example) will not draw more than 12A continuous if they’re meant to run continuously (3 hours or longer).
https://www.se.com/us/en/faqs/FA104355/
Very true. My computer says 240V on it, so I should only use it up to 192V.
Interestingly, the peak voltage of 240V AC (typical) is 330ish+ volts.
Typical house wiring is required to handle 600v due to voltage transients and wear and tear.
So any component rated to 240V dc will fail immediately on AC, and even 400-500V DC is not a good idea.
I guess there is a reason there is a whole category of engineers for this kind of thing.
No, you just shouldn't assume that that's the case. In the case of a computer and mains, both of those are nominal voltages and there will be a range of voltages which are expected to function, and if you want to check for sure, you should check those ranges.
The point is, voltages are usually a 1:1 match. That includes when you're working with ranges, you want the supply range to be inside the load range.
And even for amps where you see that 80% rule, that's for keeping the load smaller than the supply. Solar panels aren't a load and don't work that way.
This feels a bit like the logic behind "do not put hamster in microwave" warning labels.
I think if you work with electrical or electronic systems in practice, you learn pretty quickly to respect tolerances and that data sheets are a map, not the territory.
Also, electrical installations are usually seen as a field that should be done by trained personnel, not arbitrary laymen home owners. So I think the appropriate reaction would be to remind people that they should hire an electrician to do the installation, if they don't have the necessary specialized knowledge themselves.
Actually if "you work with electrical or electronic systems in practice" you get pissed off at everything for how dumb it all is: 12V DC batteries are more like 14 nominal? AC wall plugs dip voltage when printers turn on, random equipment you arent even sure in the building can trigger UPSes based on unknown settings in the device? International standards and communication protocols mean nothing as "a standard" because each company has their own entire list of bugs/implementation mistakes. All the international enforcement certifications care way too much about inconsequential bullshit and miss all the true showstopping problems in most industries?
This world is amazing anything runs at all. The slightest addition of complexity is causing everything to fail now.
Modern computers are less reliable than ever, some companies have decided to REMOVE the pinhole bios reset (that has been around for 30 years) at the same time as things are buggier now and dont boot again until you physically unplug the bios battery deep inside and hard to get to.
The modern engineer:
It works! OK, stop touching it. We don't want to break it.
This is what makes software engineering so seductive, everything works exactly as it was designed to (whether intended or not). Imagine trying to program for computers with memory that drifts values progressively more as it wears down.
Spoken like a true professional!
So on the one hand we have a product which isn't even remotely designed for the use case (hamsters), and during normal use shows obvious behaviour (cooking) that should imply risk to said hamsters. On the other side, we have a product designed to be installed in an electrical system, and shows no signs during normal use that it's installed unsafely, and where the advertised specs are not actually safe for normal usage.
Whether or not the company in this case shares some or most of the blame with novice users - the analogy is not a great one.
Microwaves were originally specifically invented to microwave frozen hamsters:
https://interestingengineering.com/videos/1950s-reanimating-...
Hyper amusing, thanks for sharing! Doesn't really improve the analogy, but fun quirk of history :-D.
As Doc Brown would say, "Great Scott!"
I have the impression these are consumer products so I would them to be designed to be installed by people who do not normally work with electrical systems. If they are only sold to tradesmen that would be different.
Yeah, it would be important to understand who the company is intending to sell to or do the installation.
Though the lines are often blurred, because I guess most companies would like to sell directly to end customers, even if their product requires a professional to install.
Even IKEA does this. You can go in and buy an electric stove and oven, grab them from the warehouse and take them home with you right there. But it's a bit of an illusion: You're still supposed to call an electrician to actually connect the things.
> Yeah, it would be important to understand who the company is intending to sell to or do the installation
You can do that by just reading the product page[1]. The delta pro, the equipment in question, looks like a plug-in appliance. It visually communicates that it is portable (by having a wheel and a handle) and by virtue of having a power lead connect to it it communicates that you can just plug it in. They further reinforce this by writing this: "Plug & Play home backup solution". "Easy installation with completely pre-wired Plug & play home backup solution" "The solution provides a convenient home battery system without rewiring or running dangerous extension cables through your home." "Plug directly into an AC wall outlet and make sure that the wall output current is more than 15A."
And on top of that the manual[2] makes no mention of needing an electrician.
In contrast an IKEA electric oven's product page[3] states this: "No plug is included. Installation to be carried out by a qualified installer." and then the manual[4] states "Installation, including water supply (if any) and electrical connections, and repairs must be carried out by a qualified technician."
But of course nobody reads the manual. The big difference is that one comes with a plug while the other doesn't.
1: https://us.ecoflow.com/products/delta-pro-portable-power-sta...
2: https://websiteoss.ecoflow.com/cms/upload/2022/10/12/1312845...
3: https://www.ikea.com/gb/en/p/mataelskare-forced-air-oven-ike...
4: https://www.ikea.com/in/en/manuals/matalskare-forced-air-ove...
If you can do a code compliant installation, then you’re the customer. If you can’t, then I’d suggest hiring an electrician.
I don’t know about the components they’re selling, but with electronic components, it’s on the buyer to properly read the data sheet and understand what the quoted nominal specs mean.
Unless it’s safety critical, you usually don’t want a system with a bunch of active electronics to prevent someone wiring it up wrong, because those components will interfere with whatever you’re hooking it up to, such as the MPPT, the battery, or whatever else.
This is like how AA batteries have a nominal voltage of 1.5V but the actual open circuit voltage is 0.9V~1.65V depending on charge level, temperature, etc. If you connect an AA to something that’ll explode at a voltage of 1.55V, that’s on you.
Similarly if you buy a 470 ohm resistor, you will find in on the data sheet that’s usually at 20°C. To know what it’ll be at any other temperature, you’ll need to use the temperature coefficient to calculate it.
In your AA batteries analogy, this is like saying that you do not need to state that the device exploding at 1.55V would do so, not about battery declarations (panels in this case).
It wasn't meant to be a direct analogy, just a simple example of how you get similar situations in general with electronic components, or really any kind of non-standalone component in most industries. Another example is fuses: a fuse rated at 20A will not immediately protect the downstream once load exceeds 20A, but rather, there will be a curve defined with respect to its nominal rating which defines how long it will take to burn out for any given current and ambient temperature. You may find at 20C, it will not even burn out at a continuous load of 25A, and at 30A it might take 2 hours. So if you're buying a fuse to protect a sensitive downstream circuit, you need to take that into account and use a fuse that's nominally smaller than the load you're running.
Essentially the "nominal" behaviour is not the actual behaviour, it's just a quick way of summarising the characteristics in a way that someone familiar with the class of item will be able to understand what they're buying. Another similar situation is timber sizing, where a 2" by 4" is actually 1.5" x 3.5".
In the case of electronic components, the actual behaviour will be either documented in a datasheet or just common knowledge in the industry. For example if you're buying a standard li-ion battery with no active circuitry, you'll often find the datasheet quite lacking in details because you are expected to just know the characteristics of the li-ion chemistry provided the basic parameters are provided.
Got it, thanks for diving deeper!
This isn’t electronic components, this is sold as a consumer level gadget that anyone can use. No one expects a standard consumer to understand data sheets like that.
You started off by saying you don’t know about the components they’re selling - but that turns out to be absolutely critical to understanding the context here.
Either way, I can’t believe they just let it fry the main board instead of having a sacrificial fuse or equivalent go first in these scenarios, whether it was a product aimed at professionals or not. It’s just dumb.
I don't know how this would be perceived in the US, but in UK/Europe this wouldn't be seen as or regulated as a "consumer level gadget".
It's a main-voltage electrical system. I'm not even sure it would be legal for an electrician without the appropriate qualifications to commercially commission one of these systems. Their website even says installations should be performed by "a licensed electrician or a qualified professional."
In practice, every single solar system I've seen is exactly the same as this one.
A fuse wouldn't help here because they're current protection devices but we're talking about voltages here. Voltages are harder to generically protect against with a sacrificial device, and also over-voltage protection devices themselves have a habit of catching fire even when the voltage is within limits so you probably don't want one right next to your lithium batteries anyway. You'll even find most consumer devices don't have much in the way of continuous overvoltage protection.
It's typical when commissioning solar to just "protect" from panel overvoltage by ensuring your panel outputs are well within the margin of your MPPT (this device appears to be an a combined MPPT, inverter and battery) on a worst case cold day. Really there's just no reason to run your panels right up against the MPPT max voltage.
Given how easy it is to protect against design overvoltage by designing your panel circuits suitably, and how overvoltage protection devices are themselves a point of (potentially catastrophic) failure, I think it's pretty hard to make the case for including one as standard, which is why nobody does.
But leaving this particular issue aside, these devices are totally not suitable for consumer installations unless you like fires.
Maybe it would be a good idea to at least add a pair of MOSFETs (one for each rail, + and -) and a voltage meter? Like, the voltage doesn't rise to maximum instantaneously, there should be ample of time to detect voltage rising to a critical amount.
So say, the input is rated for 150V, spec the components to sustain 180V, and trigger the MOSFETs to disconnect the panels at > 160V.
And maybe also add a big ass buffer capacitor, that can be used to soak up a bit more energy in the case of an inrush spike before the MOSFETs actually disconnect.
MosFET's or IGBTs are likely what failed. And, capacitance is something you do not want on a string of PV.
DC starts getting really nasty to deal with somewhere between 36-52v, with 150v of panels not being something joe-blow should be able to buy on amazon. Designing these systems to be safe is difficult.
> Not everybody buying these has a Ph.D. in physics and if it says 148 V on the label and 150 V on the other label then it's your product that has a problem, not the customer.
Idk. I don't have a PHD, but 220V sounds like 240V to me. I wouldn't do this.
I feel like getting advice about how to wire up electronics should not be so hard.
> Maybe they should just improve their product to make it more resiliant
Adding "resilience" usually adds to the per-unit cost. I think making a web page adds some cost too, but at least that can be amortised.
> And no matter what happens, customer support should help the customer, not blame them.
I think that's happening here: Making a web page to educate future customers seems like a really good idea. I wouldn't have thought that necessary until I saw it, but I'm always excited to learn something new.
The existing customers who did dumb should consider this a relatively cheap education in electronics; cheaper than a PHD at least!
Also, whether the company also gave them rebates or credits we don't know here, but telling "customer support" they "should help the customer" is also telling them they're not helping the customer, and you don't know that.
To me, 220 sounds 20 like lower than 240. I have a hunch that this might be a common perception.
US appliances using single-phase power work between 208V and 240V so they work on both residential and commercial electrical systems.
Line-to-line voltage on a three-phase 208V system is 208V, line-to-line on 240V single-phase system is 240V.
Most commercial lighting products are rated for 120V-277V so they work on both residential and commercial (480/277V line-to-neutral single phase voltage is 277V)
Really?
I have all sorts of electronics that say everything from 208V - 240V that all go in the wall, so I think all those numbers are probably close to each other in whatever a volt is.
I think if I'm worried about a limit of some kind, being within 5% of that limit seems like I might as well be over-limit if the commonly seen distribution I see in my house is greater than 15%
I have a lot of electronics that accept 100-240v doesn’t mean I think they’re close together, just that they have compensating mechanisms to handle such voltages.
The margins are generally lower for higher power devices because the electronics are more expensive. Thankfully these electronics in general are becoming cheaper which is one reason why they’re ending up in the hands of people inexperienced with them.
Also try to tell someone they need an extra 30% in margin and often they'll think they’re being upsold.
> I have a lot of electronics that accept 100-240v doesn’t mean I think they’re close together, just that they have compensating mechanisms to handle such voltages.
I bet you also have a lot of electronics that don't though, and those that do probably say so.
My kitchen mixers, dishwasher, washing machine, driers, rice cooker, refrigerators, sauna, and pool pump aren't that tolerant by a long shot. I've got a few computers with a switch on the back to choose between 220v and 110v.
Plugging something that takes 110v into my house breaks the thing, so I've learned to check.
But I don't have anything that's 208v that can't go into the house. So I think whatever the situation is with volts, within 15% is "basically the same", so coming within 15% of the rated limit, is probably just like exceeding the limit by 15%.
And so this is why I would not expect something at 146V to be under the safety limit of 150V.
> Also try to tell someone they need an extra 30% in margin and often they'll think they’re being upsold.
Where do you get 30%?
You’re listing things that are high powered and or old. Modern PSUs don’t have that switch. While it’s in the early stages I expect more white goods to switch to BLDC motors which will likely use voltage transformers that’ll support the 110-240v.
People generally are not lugging white goods internationally, the average persons experience with different voltages is for laptop and phone chargers when they travel.
But for the matter at hand, the margin mentioned is needed on the solar systems, this is where the inverters can get expensive, which is why it can look like an unnecessary upsell to people who’ve never blown a device before.
> You’re listing things that are high powered and or old.
Sure. I have high-powered and old things, and I bet you've seen stuff like that too.
I'm explaining why I, as a non-expert, would not put 146V into something that says it can't take more than 150V.
> People generally are not lugging white goods internationally
Travel doesn't enter into it; My appliances came from Europe, they're just labelled a bunch of different voltages, so I think voltages within that range are roughly equivalent.
Furthermore, British have such a very special relationship with tea, such it would be entirely understandable that a Brit would take their kettle with them and often become quite annoyed that they cannot get an adapter to use it when holidaying amongst the yanks.
Not sure what I expected from someone who thinks 208V and 240V are close together from some labels they saw on some devices.
> Adding "resilience" usually adds to the per-unit cost.
In this case, the cost is much less than a dollar (say, a varistor that blows the existing fuse) and it prevents a catastrophic failure.
But they want you to have to buy another one.
Why does this kind of comment get downvoted that pinpoints the actual motivation? We just pretend that planned obsolescence is history.
Because it’s an extreme claim backed up with no evidence. Hanlon’s razor applies here.
Also see Hitchens' razor and Russel's teapot.
At least in parent's case, probably because the vast majority of their comments are black-and-white hot takes that are always downvoted regardless. And they basically never respond when asked for any sources.
Yeah bad faith commenter then
Voting based on ad hominem is against HN guidelines.
I’m sorry who did you mean to say this to? Not sure this is relevant here
They're just being cheap. If you're going to let customers plug panels directly into your box you should have overvoltage protection. It's that simple.
> Making a web page to educate future customers seems like a really good idea
I don't think this is an official website of ecoflow.
Other than that I agree. I don't think asking for a bit of knowledge from the customers is a bad thing. A warning in the manual about safety factors should be enough.
> Idk. I don't have a PHD, but 220V sounds like 240V to me. I wouldn't do this.
220[Vrms] * 1.414 = 311[Vp-p] btw. HOW!?
Besides the ratio between the peak and effective value, you must also account for the standard tolerance of the nominal value.
The actual maximum peak voltage for the European mains, is 230 V * 1.15 * sqrt(2), because of a 15% tolerance. That is about 375 V. With a small safety margin, the minimum voltage rating for components connected to 230 V a.k.a. 220 V is of 400 volt.
Makes me wonder if that was how EV DCFC quickly settled with 400VDC. The voltage makes sense if it was somehow known that engineers has intuitions with safe designs for 400Vp-p systems.
I would be wary of relating any DC constraints to AC constraints and behaviour.
So the issue is that 220V is nominal in China, 230V nominal in UE and 240V is UK/part of Australia. So if anyone is preparing product for global market (as most are doing now) more likely then not will support all of this voltages. Thus is kind of normal (but wrong) to assume 220V sounds like 240V.
When the voltage was unified in UE, the nominal value was set to the median of 230 V, but its tolerance was raised from 10% to 15%, so that the new maximum peak value of 230V + 15% will match the old value of 240 V + 10%.
So now for all 220/230/240 V standards you have the same maximum voltage value that is used for electrical designs (about 265 V effective), so they are equivalent, regardless of the name.
True, however there is also old equipment. For example I have heard that light bulbs designed for 220V will last for noticeably shorter period of time ar 230V nominal circuit. That is why it is worth to check supported voltage. But you are right - newer equipment will suport all voltages.
Many charguers are now 100-240V, 50-60Hz, that is close to pluggable anywhere on Earth. (I burned one or two a long time ago, when I forgot to check and used a 120V transformed here with 220V)
Same thing happened to PC PSUs. I don't think there is a recent unit that still has the self-destruct voltage selector switch which pops them if you are in 230V land (and the switch is set to the smaller setting).
AC wiggles and wobbles.
Why doesn't this just produce a shutdown? Inverters have to track voltage and current on the input and outputs sides, and can turn themselves off. They shouldn't be that close to the absolute maximum voltage ratings on the components.
Too much current is a heat dissipation problem, and you've got some time to deal with that, at least tens of milliseconds.
Anyone have a teardown on these things? Are they using under-rated MOSFETs? That's all too common in solid state relays from China.
High voltage, low RDSON FETs are (slightly) more expensive, and these products are cheap. A better design would use a higher-voltage rated input switch with poor (slow) switching performance, like an IGBT. Don’t design critical infrastructure around EcoFlow hardware.
Fujitsu, which sells MOSFETs for this application, writes: "Firstly devices should be rated at 600V or 650V, as this will generally provide more than adequate protection against the threat of high voltage transients."[1] That's a nice big safety margin. It should hold until the voltage monitoring shuts the whole thing off.
Not seeing UL certification on this thing.
If we're going to have US protectionism against China, a good first step would be to require UL-type testing, carried out in the US, on all imported electrical devices that run on more than 12VDC or contain a battery chemistry capable of thermal runaway. Electrical safety is a solved problem if you can keep people from cheating.
[1] https://toshiba.semicon-storage.com/eu/semiconductor/design-...
The voltage ratings of the MOSFETs used for 220/230/240 V applications have been increased over the years.
Decades ago, when bipolar transistors were used, they were rated for 350 V, which is barely enough for 220 V + 10%.
When everybody started to design universal converters usable for 220/230/240 V, the ratings were increased to 400 V. The first power MOSFETs were also rated thus.
Then there were too many converters destroyed by random voltage spikes, so the standard ratings were increased to 500 V. That proved to still be not enough in many places over the world, so the ratings were increased to 600 V or 650 V, already many years ago, in order to make extremely unlikely the destruction of the transistors by voltage spikes much greater than the nominal mains voltage.
600 V or 650 V is used for converter topologies where the transistors see only the peak input voltage. For converter topologies that use fewer transistors, but those see peak-to-peak voltages, the rating of the transistors must be 1200 V.
For 650 V, gallium nitride FETs are the best available devices, while for 1200 V or higher voltages silicon carbide transistors are the best. Silicon transistors are the best only for ratings much lower than 100 V, but they may be preferred also at high voltages for being much cheaper.
My understanding is that mosfets themselves are usually not UL certified/listed. I recently did a UL certification of a power supply and the IGBTs we used were themselves also not UL certified. The UL certification was more about the overall system design.
> They shouldn't be that close to the absolute maximum voltage ratings on the components.
This appears to be a situation where the engineering team determined the absolute maximum input voltage and the marketing/product people put that number straight into the documentation.
Standard practice with electronic parts is to determine the absolute maximum rating, then to specify a recommended maximum that allows for some safety margin and variation.
Instead, this company determined the absolute maximum and then just shipped it.
One way or another, many of us are in agreement the company screwed up and it’s on them to fix it - whether that’s their marketing, their manual, their lack of over voltage protection, whatever it is it’s their fault.
Yet so many people in this thread are so keen to blame the customer, it’s pure ego from them. “I’m too smart for that to happen, so it’s all their fault!” they sneer. Classic bad faith forum behaviour…
That's humanity in general. But yea- general guide says "add up your open circuit voltage and don't exceed that." If something fails because of the panel manages to get more than 1000W of solar flux, and is cold... it's the mfgr's problem.
I need to actually look up why the extra flux increases voltage. Maybe it really doesn't but just moves the MPP to a higher voltage by having more current.
> Plugging in four 400w solar panels in series is similar to filling your gasoline powered car with diesel and wondering why the car manufacturer isn't replacing your new car.
I don’t think this analogy works. The solar input works like Diesel or Gasoline in different temperature. It’s pretty unreasonable to assume the consumer knows when depending on temperature unless the explicitly state in the manual (I’m willing to bet good money majority of the people in US have never read their car manual either)
Agreed. No one needs to change which type of gas they use because it happens to be a warm sunny day.
Yeah car analogies suck.
Diesel is blended differently for winter and summer in many countries. See this for instance https://www.crownoil.co.uk/guides/winter-blend-vs-summer-ble...
Around the skiing season, many automotive magazines will remind diesel drivers to buy “winter diesel” or use additives if e.g. driving up to the Alps or similar cold places.
It’s not so black and white :)
Straight Vegetable Oil (SVO) diesel conversions do. It'll gel at low temperatures, so they blend or switch to a separate tank of regular (or bio) diesel while the engine is cold, wait until it generates enough heat, circulate that heat along the SVO lines and into the tank, then switch over. Then switch back a few minutes before shutdown so the lines are full of regular diesel for the next cold start.
True for gas not for diesel. You have to switch to winter- or arctic diesel if the temperature goes below -20c.
Gasoline is also blended differently for summer or winter. It's not as crucial as for diesel, but it does make a significant difference.
In the Corvette community, using a higher octane fuel on hotter days is well known to prevent ping.
I'm surprised the Vette doesn't call for high octane all the time. It's common for high compression engines.
The knock sensor on LT1 and later engines allows one to get away with lower octane fuel for day to day driving.
Because they run their engines well within the margins of their design. If you were running at the edge of the envelope you would find that the temperature does matter.
I love a good analogy. This is not a good analogy.
I'm not sure I know what a good analogy looks like. If the two things are identical, then the analogy is uninformative. If they're at all different, you will zero in on the differences rather than the similarities.
Sometimes they can be ok pedagogical tools, but they're easily misused as tools of persuasion.
You’re not supposed to zero in on the ways in which an analogy doesn’t apply. You’re simply supposed to read the analogy in order to see what it’s attempting to _highlight_ about the scenario.
This is a common pet peeve of mine, people not understanding how analogies are supposed to work and getting distracted by the differences. They’re supposed to work like a light filter placed over a lens, something will be highlighted and focus on that, don’t focus on the fact that “but all the colours are different now!”, the only purpose of using the light filter was to highlight a specific part of the image, the fact that it also coloured everything wrong temporarily is supposed to be ignored.
You know, just to use an analogy to explain analogies. Gotta be as meta as possible.
a better fuel analogy would be to run e85 in a non flex-fuel car.
(certain fuel systems components will be degraded by high ethanol gasoline)
I was going to comment on the manufacturer's safety margins, but then I found a graph [1] on the variability of voltage vs temperature and it seems to be a lot steeper than I thought/expected, to the point that I'm wondering how these do not require either training or a voltage regulator to install and operate properly:
https://www.researchgate.net/figure/Module-voltage-current-v...
They do!
Basically anything that consumes solar power incorporates what's called a "MPPT", or maximum power point tracker.
Basically, it's a smart DC-DC converter that continually tracks the voltage/current output of a solar panel and adjusts the load to extract the maximum available power from the panel.
It's not uncommon to have issues with extremely high panel voltages in snowy climates, when they're first illuminated in the morning. If you are close to the maximum voltage your MPPT charger can handle in normal circumstances, extreme cold can even damage things during the initial morning transient. You then have to do oddball things like use a crowbar system to prevent blowing up your MPPT system.
(see https://en.wikipedia.org/wiki/Maximum_power_point_tracking )
Note it would be sufficient to shut down (short-circuit) a single panel, which is safe, to lower the overall voltage.
Another post commented but that’s exactly the point of the MPPT. Not only is it temperature dependent but solar incidence angle matters too (how the sun angle is relative to the surface). MPPT works by changing the internal impedance to match the ideal charging voltage. But there’s a limit to how much it can regulate but I think it’s very fair that a consumer would expect nominal voltage times panels in series is less than the marketed solar input to work.
There's a reason people don't install electric equipment without training.
This is just like not upsizing wire gauge if you have a bunch that are loaded simultaneously buried together in a somewhat insulating wall. Without the burying under plaster, everything would be fine. But combine that with simultaneous loading during summer, and you fry/roast the PVC insulation.
> There's a reason people don't install electric equipment without training.
I’m not sure if I follow that logic and if your analogy follows. I would argue this is closer plugging in an appliance rather than running wires. If I run a 15A appliance on a 10A breaker, a normal person without training would expect the breaker to trip. This is like running a 10A appliance and the 15A breaker trips because the appliance is sometimes 16A when it works in the cold.
> If I run a 15A appliance on a 10A breaker, a normal person without training would expect the breaker to trip.
Would the breaker trip in this case? I thought in this case it'd be more likely to start a fire.
Edit: thinking about this more, I think I'm wrong. A fire would start if your wires were too thin for a given amperage. Breakers detect current flowing.
Yeah, you were wrong: 15A on thin wires would heat them up too much and could cause a fire after prolonged runtime.
A 10A breaker breaks the circuit much faster than it takes for the wires to heat up, thus stopping the current flow.
The part that they are warning about burning out is a voltage regulator.
Those things are normally built to handle a nominal 115 V assembly of panels. There's probably something on the manual about this, but when you put a giant label saying your device supports 150V, people are not going to read the manual.
Sounds to me like someone is misrepresenting their products. A solar panel's VoC should be its maximum possible output in ideal conditions (open circuit). If that's under your product's maximum input voltage, it should be no problem. Ever.
Is EcoFlow advertising a higher input voltage than their products can actually take, assuming most people won't actually reach it due to temperature inefficiencies? That'd be false marketing, and it'd make this article manipulative, false blaming of the customer.
All solar panel datasheet have temp coefficient, eg for one random ecoflow solar panel:
source https://websiteoss.ecoflow.com/cms/upload/2022/10/15/-139121...STC ("standard testing conditions" for solar panels) is 25C so if it's freezing 0C you have 25 multiplied by 0.33 Volt = 8.25 Volt more than STC in open circuit situation.
Unfortunately inverter manufacturers seldom document how many Volt will destroy the MPPT and up to how many Volt the MPPT will safely turn off by itself before breaking.
Not to mention a fail-safe MPPT would/should just crowbar the input if there's any potential for overvoltage.
Solar panels are current sources that waste their power into a long string of silicon PIN diodes that eventually reach their forward voltage and begin to eat up all that juicy current. You can just take the current and keep the voltage as low as you want, just make sure to take all the current or it's voltage will rise to let the diodes take the current you aren't using.
> A solar panel's VoC should be its maximum possible output in ideal conditions (open circuit)
I think this is where the confusion arises - what do you mean by ideal conditions? Ideal conditions for solar generation are not necessarily at the same time as the highest voltage operating conditions. VoC tends to be specified at Standard Test Conditions which has light-levels representative of a sunny day (1000 W/m2) and a cell temperature (not ambient) of 25 degrees C, which is already a lot cooler than most panels would typically be at that level of irradiance. So really, the label is already specifying a voltage higher than what you would typically experience during times of max generation.
However, the max voltage could exceed this rating at times when there are cold ambient temperatures with enough light for the module to function, but not enough sun to meaningfully heat the cells. So in this scenario you may have maximum voltage, but you're far from maximum power nor at 'ideal conditions'.
What does “maximum possible voltage” mean for a solar panel? Do you include things like cloud edge effect (which increases incident light beyond direct sunlight?) What about installs with a nearby window reflecting light onto the panel? Do you include ultra-cold environments (which will reduce the resistance and therefore often increase voltage, although admittedly not, I think, Voc)?
VoC is the maximum potential voltage a cell is physically capable of producing. It does not consider real-world conditions. Rather, real-world conditions cause the solar panel's output voltage to be somewhere between 0 and its VoC.
Voc is just the open circuit voltage measured at the terminals (plugs). “Nameplate” Voc is at standard test conditions (STC) of 1000 W/m^2, 25 deg C cell temperature, and a standard are mass/spectrum. The combo of 1000 W/m^2 and 25 C cell temp is not common in the real world in most climates, but still happens. Even relatively hot climates can have times in winter that exceed nameplate Voc if inverters turn off (making the panels go to open circuit).
Obviously you include everything, otherwise it wouldn't be a maximum. You can define a minimum temperature for this, of course, but the customer should know about it.
There's no theoretical maximum voltages for solar panels like there kind of is for batteries. They're just giant array of photodiodes and they just generate whatever voltage potentials proportionate to amount of lights received.
You could produce a "max voltage flying low earth orbit over Gobi with no shadows from Starlinks" value, but that's just the value for circumstantial most absurd situation you happened to have come up with, not a guaranteed theoretical maximum.
The current is what varies proportionally with the amount of light received.
The open-circuit voltage depends mostly on the structure of the solar cells and on the temperature. It has only a very weak (logarithmic) dependence on the amount of light received.
The voltage that you measure at the output depends on the open-circuit voltage, on the amount of light received and on the amount of current that you draw from the panel.
The maximum open circuit voltage for a solar cell is easy to estimate, because it happens at the minimum temperature for which it is designed and the maximum solar illumination. It can be exceeded only using a light concentrator that projects on the panel light collected from a much greater area.
So it is doubly important that all equipment downstream has overvoltage protection?
In fact considering there is no theoretical maximum, it would be downright negligent not to have overvoltage protection
Yeah, billowing magic smoke just sounds wrong. No disagreement there.
There is a theoretical maximum: the open circuit voltage of a single photovoltaic junction cannot exceed the bandgap of the semiconductor used, no matter how much light you apply. The manufacturer knows the semiconductor used and the number of junctions in series.
They produce current until the diodes start conducting given the forward voltage, as they'll take any current you don't extract off of your hands.
Of course if you want to extract maximum power you have to balance the higher worth of the current you take against the loss of current to the diode forward conduction.
Why does the Delta Pro not have a fuse on the input, with the MPPT limiting the max voltage to 150v (by upping the current until the voltage sags and/or the fuse blows, or even a straight crowbar circuit). This is a premium consumer brand selling a mostly complete product, and protecting the input from overvoltage would be straightforward. The frustration at the warranty weaseling isn't surprising.
You might think that the voltage rise could be too fast for most protective technologies to save the downstream electronics, but the general case is that the temperature slowly drops and the sun slowly rises. So the voltage should slowly approach the limit.
Adding a normally-open relay and a voltmeter and a microcontroller should fix this. Relay won't close on startup unless the voltage is safe. Microcontroller will open the relay if the voltage gradually nears the limit. Should be solvable for <$5 in parts.
Dark start (when the batteries are flat w/o grid power) will be challenging. There will need to be a small battery to power the voltmeter and relay, or a high-voltage tolerant supply to power the microcontroller and relay temporarily. A 9V should likely be sufficient.
Common relays don't handle 150VDC, and I'd spec the voltage even higher even though one would think the voltage rating has more to do with arc interruption rather than creepage while off. Also a microcontroller is complete overkill, draws too much current to be easily powerable by the solar panel side, and adds complexity for something to go wrong. A simple analog comparator suffices.
The standard answer for overvoltage protection is a crowbar circuit + fuse, and I think that's what I'd aim for rather than a relay. The problem with DIYing that is knowing the input capacitance of the Delta and finding out whether it has any other problems with its input being abruptly shorted.
No the DC/DC converter could just turn it's transistors to short out the panels and rely on the fuse you want anyways to handle idiots paralleling more panels than allowed.
Why isn't there code/regulations for tbis. Why do you need blog advice.
It is like using too thin wiring to your oven or something. Because you based it off how you typically use the oven not is max draw plus decent margin.
Which is why you get a qualified electrician who knows or get qualified yourself.
> Why isn't there code/regulations for tbis. Why do you need blog advice.
On pretty much every other device (domestic for sure, I don't actually know abount commercial) there is.
> It is like using too thin wiring to your oven or something. Because you based it off how you typically use the oven not is max draw plus decent margin.
Sure, but with all other electrical labelling the numbers are correct. Imagine if Neff said "you only need an 13A rated socket" for their oven, and then when you want to bake bread it draws more. That's very different to Neff saying "you need 45A", and deciding to install it on a 13A socket yourself because you don't need to make bread. The former is what's happening in this case.
Okay, but the oven tells you: use at least 8mm^2 wire, and then it goes up in flames because hey sometime you actually need 10mm^2...
[flagged]
Most household solar systems do require permitting and inspections before you can turn it on. There are some exceptions in a few states for very small systems now. Ecoflow provides equipment for these small legal unpermitted installs.
More importantly, equipment shouldn’t self destruct in a dangerous fashion when pushed over the limit.
A lot of people here are saying things are mislabeled, but every single solar panel comes with a datasheet that shows its Voc and temperature coefficient.
Solar panel manufactures can’t give you a hard maximum on voltage because temperature will make that vary. Anyone who is buying solar panels without understanding the temperature coefficient shouldn’t be buying solar panels. It’s not hard to understand and there are hundreds of guides out there explaining it if you just search for terms on the datasheet.
When I got solar panels for my (former) house 15 years ago, as I recall, the best practice was to have panels in parallel (each with its own microinverter) and not in serial as serial would cause loss of efficiency when there was partial blockage of panels. (I could be misremembering all of this).
That's only relevant if you're so starved for panel area that you can't put them into places that have each sub array sufficiently homogeneous and only partially shaded during sunrise/sunset.
you might be misremembering bypass diodes?
No, microinverters are still a thing (Enphase is a popular brand) and they do then get connected in parallel.
There are also power optimizers which are DC-DC and connected in series.
I am sure many are familiar but I found it amusing when someone explained to me why it is called magic smoke.
It is because electronics work through magic so when you let the magic smoke out, they stop working.
I’ve never heard it called magic smoke before, but a regular saying at one of my old jobs was “ah yeah we let the smoke out” in relation to 100% electric drive vehicles. Smoked many inverters, shorted 96v bus to a 24v bus, etc.
It was almost a rite of passage to “let the smoke out” in that org. That job was actually great because as a software engineer I happily spent a lot of time with a fluke, a wrench, arm buried in the bowels of a vehicle fishing out sockets, etc. Writing the software was not the hardest part of those programs, but being one of the handful of folks that knew the entire electrical, cooling, mechanical, and software systems made us the most valuable folks on the program. We had to know all those things in order to write the software correctly.
In the early 80s we used to say electronics ran on magic pixie dust, and when you let the pixie dust out as smoke, the magic went away.
Hackers dictionary: http://www.catb.org/jargon/html/M/magic-smoke.html
Devices run on magic smoke. When something bad happens the smoke escapes and thus the device no longer works.
This is proven by observation - the only thing you see charge is the smoke escaping.
The presentation helps a lot too, the way I was told it was something like:
“Did you know that computers actually run on magic smoke? Once the magic smoke comes out though, it stops working.”
It's the soul leaving the IC.
On the other hand, properly designed solar can do surprisingly well surprisingly far north.
Here's one in Tromsø Norway, well north of the Arctic Circle.
https://cleantechnica.com/2025/09/27/bifacial-rooftop-vertic...
What we’re seeing here is the mismatch between component level specs and end user ratings. A device which is rated to 24V input power will probably tolerate up to 32V and it surviving 60V would not be uncommon. A component with a Vmax of 24V probably explodes if it sees 25V.
Calculating temperature correction is in both the NEC and CEC. Here's the CEC version:
64-202 Voltage of solar photovoltaic systems (see Appendix B)
1) The maximum photovoltaic source and output circuit voltage shall be the rated open-circuit voltage of the photovoltaic power source multiplied by 125%.
2) Notwithstanding Subrule 1), the maximum photovoltaic source and output circuit voltage shall be permitted to be calculated using a) the rated open-circuit voltage of the photovoltaic power source; b) the difference between 25 °C and the lowest expected daily minimum temperature; and c) the voltage temperature coefficient as specified by the manufacturer.
This is not a problem in a properly dimensioned system at all.
It is still well within the 'engineering reserve'. Solar panels produce the most power in mid March, when they are cooled very well by the ambient air but the sun is already lining up nicely with the panels at mid-day. But those conditions are pretty rare, and most inverters will handle this gracefully by simply dumping some of the excess power as heat - or in the better ones, by simply chopping the input voltage at a high frequency. This allows for very fine control over the average power and will help to keep the voltage under the isolation break down voltage (which usually is a very large factor over the voltages that you see in practice).
My own system is 50 panels, 1000V maximum on panels that nominally produce up to 100V, so I never have more than 8 of them in series. That leaves 200V to play with and I've never seen it get close to that 1000V. The inverters are easily capable of dealing with this and if the strings were to ever exceed 1000V then the inverters would simply disconnect those strings with their internal disconnect relays.
So, in closing: don't run your system 'on the limit' or rare conditions will push it over the limit. But even if you do: inverters are fairly bullet proof nowadays and if you over-volt the input the vast majority of the ones that you can normally buy are going to just switch off and move to an error state that will require you to power them down before they will be usable again.
To flip this into a potential solution to a wider problem-- global thermal balance-- combine solar panels with radiative cooling.
https://www.sciencedirect.com/science/article/pii/S258900422...
https://www.pv-magazine.com/2025/01/13/daytime-radiative-coo...
https://web.stanford.edu/group/fan/publication/Li_ACSPhotoni...
Ah yes, a paper from Fan Shanhui's group at Stanford, which kicked off the whole business. Should have linked that instead!
This is 5.7 deg (using metasurfaces to selectively reflect reflect absorb different wavelengths)
compared to a less fancy 4.9 deg from their seminal paper (2014)
https://www.nature.com/articles/nature13883
Maybe comparable cooling can be achieved with even cheaper techniques..?
The interesting implication is that PV has more upside growth potential than nuclear, against the ultimate limit of global thermal pollution.
Where to start, eh! So most everything to do with off grid specifications can be listed as "nominal", ish, depending on, etc.Not knowing this means that persistance will provide the circumstance to be educated. There are a number of ways to get things wrong and melt stuff, or get hurt. Batteries should always be treated as unpredictable dangerous beasts, happy as a clam if they are treated just right, but capable of producing trouble and disaster, or just del8vering a viscious bite to the unsuspecting and surviving to do it again. A 48volt (nominal) battery bank will happily turn the required 10mm wrench into single demonstration of a wide range of metelurgical and other phenomina. For fun on a cold morning take the leads from a 3 kw solar array, off, and then strike the wires to produce a realy big fat arc, h3y hey! The simple fact, that I tell enthused,nice, but clearly unprepared people who express interest in "off grid", is that I do it, but it's not for everybody, as there is a significant technical learning curve, plus the required physical skills to mount panels, run wireing, deal with battery banks,set up the systems, and if costs are to be kept to a minimum then source parts from distributors or import directly.
I can imagine future solar panels sending spec data to the MPPT using Power Line Communication (PLC), allowing the system to shut itself down gracefully rather than dying. Rapid-shutdown systems already send keepalives using PLC today.
But then it goes all Black Mirror, with manufacturers restricting solar-panel operation to approved devices only, and UIDs being used to enhance shareholder value through recurring subscription revenue.
The MPPT could just short them out and it'd be fine; solar panels are a current source with a huge string of non-light-emitting diodes wired in parallel with the output happy to soak up any excess current around their forward voltage.
(Technically the current source in question is _within_ the diode's junction capacitance.)
Solar inverters could be designed smarter.
Today's inverters have a volt limit and an amp limit and you must stay within both.
But physics doesn't require that - you could instead design a solar inverter where you could stay within either!
It would work by detecting when one limit (volts or amps) was about to be exceeded, and pushing the operational point away from there. Remember that for solar there are two zero power - ie safe - points. I=0 is the usual one, but V=0 (ie short circuit) is equally safe for solar panels.
So this hypothetical inverter would operate between one of the safe points and the max power point.
Obviously whilst installing the system and humans unplugging wires, the V=0, huge current safe point is impractical. But that's why you have breakers.
Worth noting that the physics of electricity has an odd symmetry between voltage, power and current which means almost any circuit can be redesigned to effectively switch around all V's and I's and still work.
It is mere convention that we have decided that V should usually be regulated and constant and a property of the supply whilst I is variable and determined by the load.
Chemical batteries naturally supply a fixed voltage. You can have a fixed voltage over an open circuit without losing energy.
The cause of this problem is the standards for Solar Panels, that has the outputs measured at 25C so they are comparable with each other. The specification sheets for panels do list their peak voltage in other conditions but all the advertising is based on the standard. Solar installers know about this and size accordingly but your average consumer doesn't and is very quickly going to get into trouble with this.
I think what Delta needs to do here is accept that the standards mean all Solar will be sold this way and appropriately oversize the inverter so that it can cope with -10C sunny days. Yes its annoying for them but the reality is devices sold to people who don't know how all this works need to compensate for lack of expert knowledge in its user base.
I never tried the solar charging on my ecoflow so this fragility surprises me a bit.
I've been able to run laundry in a machine with a 1/2hp motor using the inverter side on multiple occasions. No smoke or funny smells. My 2200w generator would trip out the instant the spin cycle tried to start.
The solar panel with inverter does not have any inertia so it can survive power spikes more easily, can lower the voltage till it's over. The generator on the other hand has physical rotating parts that could be damaged by sudden torque asked by increased load. Of course it could be mitigated with additional "soft start" circuitry on the motor but that's usually not included. Not capacitor alone please, you risk more damage.
Slightly OT, but how big of a capacitor would be needed to smooth out those current spikes? Solar-friendly could be a selling point for some appliances.
I wonder if such a capacitor could even be retrofitted.
A capacitor wouldn't help in this case. They're most useful when you need to overcome transient situations like a locked rotor, not when you have a heavy drum that needs to be spun up from zero. During this phase the machine can consume well over 2kW of power for a few seconds. The circuit is rated for continuous 15A, but it has no problem supplying 20 or 25 for a brief period of time.
I'm sure that home mains would have no problem, but a solar installation might. Would a small li-ion help smooth over those amperage hills?
It would help at noon, when usually inverters make so much power they push the local grid to saturation which causes them to disconnect from the grid for a while. There are different rules for this for different localities, typically the installer will pick the regime appropriate for the local grid. Where I live (NL) the voltage is allowed to hit 253V for up to a minute, if it takes longer than that my inverters will switch off. That's a requirement to pass inspection, if your inverter can not do this then that's an automatic fail.
There are 'home batteries' that store power for practical reasons up to a day, maybe two. They are useful for sunny/cloudy conditions to maximize the amount of power locally consumed. But battery storage and retrieval isn't free and so far - at least, for my installation - this does not make economic sense. But another factor of two in price drop for my preferred chemistry and it definitely would make sense and then I would probably install about 20KWh worth of capacity. The trick then becomes to balance power sent to the grid and sent to the battery so that you maximize the utility of the grid in order not to wear out the battery prematurely. That means cycling the battery between 70 and 90% state-of-charge for Lithium-Ion. I'd much rather have Lithium Titanate so that is what I'll be holding out for, they are already available, but still too expensive. But they're much safer and have far better charge/discharge curves and life-span.
I actually meant a small li-ion inside the appliance, to smooth out the load. Do any batteries support 20C or 30C? That seems like enough to smooth such a load.
That's a very complex and potentially dangerous device.
I see, thanks.
The problem would not even be making it initially, the problem would be to keep it safe in the long run. I am not a huge fan of all these embedded Lithium-Ion batteries, they're flooding the market (and our homes) and they are disproportionally large factor in house fires.
I did not realize that was so common. A friend of mine actually had a lithium ion fire in his house, from one of those hoverboard devices.
Don't bother; at that point just plug them into 200~300 V DC right to the battery (with just fuse and meter between, no need for any conversion, the washer motor controller that'd be needed to utilize a capacitor for smoothing these spikes would do just fine on a reasonable battery charge/discharge voltage spread.
Do any home battery systems, or home appliances, actually support this?
A few years ago, I plugged a single 100W solar panel into a battery pack that advertised it accepts 18 volts. I left it plugged in, on my deck, for hours. When I came back, there was a foul smell and some parts of the battery pack had turned black, apparently from getting charred. The battery pack no longer worked at all. I was very fortunate that only the control circuit had been destroyed and the battery cells (and my deck) had not been touched.
Lesson learned: don't skimp on Li-ion battery packs!
Also, I have a question about this article. Don't EcoFlow battery packs have a circuit that checks the incoming voltage and automatically shuts off charging if the voltage is too high? I would also expect a loud alert.
Can anyone comment on the "You can exceed the amperage specs" ? I made myself a little case study using 4x1W panels and using them in series and parallel. I got the distinct impression that running panels in parallel is better in not so bright conditions compared to a single panel. Whereas a serial configuration made it worse. Since the sun doesn't shine here that much. Running in parallel seems to be preferable, but it would slightly exceed the amperage spec of a few converter i sampled.
It be worth looking up the I-V curves of solar modules on a datasheet - a key factor is that the maximum power point of a solar module (for a given set of environmental conditions) is really dependent on the voltage that it is running at (whereas the current is more constant based on the light level, up to a certain voltage), so to get the maximum power out the resistance of the load needs to be matched to achieve that maximum power voltage (V_MP).
This is what MPPT controllers do, as this maximum power setpoint will change as environmental conditions change.
The problem is usually shading, not so much the capacity of the wiring, though, if you try hard enough you can exceed the rating of the final stretch of wiring to the inverter (or the little pigtail in the inverter if you connect all of the strings at max voltage/amperage). Shading can really upset the current flow in a set of parallel/series connected panels and can cause local hotspots due to overcurrent. Usually inverters are pretty smart about this and they'll detect that you are pushing it further than is responsible and they will just switch off. I've purposefully triggered such conditions to ensure my installation is safe and I was pretty impressed with how utterly painless fault detection, isolation and recovery are in modern inverters. I also had an older one and there it definitely wasn't all that friendly, to the point that the whole thing had to be hard disconnected from the grid before it would work again.
>Plugging in four 400w solar panels in series is similar to filling your gasoline powered car with diesel and wondering why the car manufacturer isn't replacing your new car.
Ok, that is a very bad answer. Diesel fuel contains more amounts of energy per drop as gasoline, but that doesn't mean engine damage will result. Diesel fuel will not damage an engine if you were stupid enough to get it wrong at the pump. It will simply refuse to cycle until the diesel fuel is pumped out and the correct fuel is pumped in.
Maybe it’s different in the rest of the world (I doubt it), but the fuel nozzles for gasoline and diesel are different. You can’t put a diesel nozzle into the opening on a gasoline car, so it’s rather difficult to fill a gasoline car with diesel fuel.
The other way around is possible. You can fill a diesel tank with gasoline. Whether it destroys the engine or not depends on how much gasoline you put in. A gallon or two that is then diluted by filling the rest of the tank with diesel is not likely to cause any lasting damage. If you fill a tank 3/4 of the way with gasoline and try running it in a diesel you are probably going to need a new engine.
So yeah, the analogy is not good. Slightly exceeding the rated voltage and breaking the whole thing is usually not the same as putting a little gasoline in your diesel tank.
I am surprised that open circuit voltage is specified at 25°C and increases dramatically as the temperature goes down. Seems backwards! I'm looking at the Ecoflow spec sheet right now and fair enough, it's got the open circuit voltage and then the Temperature Coefficient of Open Circuit Voltage (-0.35%/°C) right next to it.
Great, guys, how about you go ahead and multiply those two numbers for me, since you're the ones writing the fucking spec sheet? It's like if car battery manufacturers only specified a cranking amps number, and told you to figure out cold cranking amps yourself.
> how about you go ahead and multiply those two numbers for me
What are you going to fill in for the third number, though? With an open-circuit voltage of 37.10V at 25°C and a coefficient of -0.35%/°C it can theoretically go up to 75V at absolute zero. And that open-circuit voltage is with an irradiance of 1000 W/m2, should we also account for the possibility of someone building a heliostat around it?
There's no one-size-fits-all number they could possibly quote. It'll always depend on the environment, because that's just how the physics work. The best you can do is provide a figure for the standardized testing environment and the relevant coefficients - which is exactly what they are doing.
At merely freezing, that solar panel would hit 40 volts. In the coldest point of the US in a typical winter, it would get up to about 42 volts. At the record minimum temperature, in either montana or alaska since they have similar records, you'd get up to about 48 volts.
42-48 is not a big enough range to give up over. My impulse is to arbitrarily pick -40 and say the normal max voltage is 45.5 degrees. Now it's nice and obvious that you can only hook up 3 to a 150 volt input, and you'll have a 9% margin of error left over. On that "first cold and sunny day" you'll output 120 volts instead of 160.
And no don't worry about a heliostat.
> Great, guys, how about you go ahead and multiply those two numbers for me, since you're the ones writing the fucking spec sheet?
No time. Busy writing blog posts blaming customers.
You think ecoflow is responsible for this website and is pretending not to be?
A solar panel is like a normal silicon diode. The voltage over the cell goes up drastically with lower temperatures. In cold climates crowbars are usually added.
Our installation from 2017 of 40 panels work great here in the middle of Sweden.
Covered in snow over the winter and generate little power November-February but rest of the year we have fine power output, with peaks May-July (obviously).
>> With mixed solar panels, lowest volts in parallel strands prevails
If a panel can hold down the voltage of others, their device should be able to do the same.
Sounds like a corner case their software can't handle. Even so, the hardware should not go up in smoke.
Why would lower temperatures lower the maximum voltage?
Sure, diode forward voltages change a little but seems like something else is going on…
It’s not that it lowers the maximum voltage that the charge controller/inverter can handle. It’s actually that the panels become MORE efficient in the cold temperatures, resulting in a (potentially unconsidered by end-user) increase in voltage, overwhelming the downstream BoS components.
Solar panel voltage goes up as temperature decreases. The chart is misleading, it's stating something like an equivalent max voltage if you think of the solar cell voltage as staying the same (and presuming your temperature coefficient matches)
I think it works this way but I could be wrong: 1. The forward voltage across a diode depends on the current, and the graph is r-shaped. For a certain diode, 0.01A might make the voltage across it 0.4V, 0.1A might be 0.6V, 1A might be 0.65V. 2. The forward voltage also depends on the temperature of the diode. For a certain diode, per °C decrease there could be a 0.002V increase.
Let's say with certain current there is 0.687V. If two diodes are connected in series i.e. (point a) → diode 1 → diode 2 → (point b), and each has a 0.687V voltage across, that's 0.687 + 0.687 = 1.374 V between point b and point a.
For the solar diodes, the "current" depends on how "strong" the sun is. If at a certain "current", across each diode is 0.687V, you'll need 216 diodes in series (between two points) to get 0.687×216≈148.4 V.
If there is 0.002 V increase per diode per 1°C decrease, with 216 diodes, that's a 0.002×216=0.432V increase per °C decrease, so with a 4°C decrease it exceeds the MPPT's limit.
Another thing about solar that differs from how diodes are "normally" used in circuits is that the "true" voltage depends on the max current achievable with the how bright the sun is right now, instead of the "true" current. When the "true" current is 0 A, the voltage across each diode might be 0.687 V. When the "true" current is 0.5 A, maybe 0.65 V. 1A, maybe 0.6V. 2A, maybe 0.3V. Try to get more "true" current, the "true" voltage drops. Try to get more "true" voltage, the "true" current drops. Power is voltage × current so when full speed charging, the MPPT uses an algorithm to find the (possibly) best minimum (not maximum) input voltage based on the temperature etc and trades voltage for current at the output. If there is no minimum input voltage restriction, solar will follow the battery's terminal voltage + cable drop instead, and instead of something like 111V, there could for example be a ~4x less powerful 25.5V (if the battery is a "24 V") with just 10% more current.
At the MPPTed min input voltage for full speed charging, maybe 111V, all might seem well even with low temperatures, but when the battery is full and there is approximately nothing using electricity from solar, the real input current will be ~0 A, so there will no voltage "sag", so the solar will realize the full voltage corresponding to the temperature and the illumination, potentially >150 V...
Lower temperatures increase PV max voltage output, not lower it. Conversely, when solar panel temperature increases, voltage decreases. So the headline specs/outputs assume to be valid at a particular temperature. As the temperature of the panels change, the realized performance changes.
It's not that little given these diodes run between sun baked summer and cold soaked winter dawn.
Last year, I did yet another PV install at a friends house. While plugging the SMA inverter to the solar field (600V), I fucked up and inverted plus & minus.
Nothing happened. I read the manual and realised that SMA inverters are protected against reverse polarity. Yeah, a bit more expensive, but well worth it
I'm more surprised you managed to plug them in reversed; did you have good reason to avoid the polarized semi-pwrmanently-latching connects that most panels ship with?
Because panels are on the roof, the inverter is on the basement, so you have to run your own cables and crimp the mc4 connectors on them. If you swap them around they get mixed up ;-)
Ecoflow fucked up, more news at 11.
This is what happens when something goes mainstream. The background knowledge that "everybody knows" when it's niche, because only turbo-nerds are into it, simply isn't common sense for everybody in the wider population.
Back when Home Power magazine started up, the panels were super expensive, and squeezing out every watt was important. Since high temperatures decrease voltage and output, keeping the panels cool (while baking in the sun!) was top-of-mind for every installation. And right along with learning that critical consideration, everyone also learned the caveat that in the bitter cold, that very same phenomenon means they can produce significantly more. Temperature coefficient was simply something "everyone knew".
Now they're so cheap nobody cares. The magazine shut down because "alternative power" and EVs aren't exactly alternative anymore, you can buy one off the dealer's lot, it's nuts. And the panels are crazy cheap now. If you lose 10% because the panels are hot, it's likely cheaper to just buy 10% more panels, than to redesign your support brackets to allow better airflow. But nobody highlights the phenomenon behind the efficiency loss.
"Everybody knew" that the ratings on the panel are at Standard Test Conditions: 25°C and 1000W/m². That's almost never the conditions in the real world, but it establishes a legal baseline whereby panels can be compared apples-to-apples and advertising kept honest (if anyone cared), but deviate from STC and output will go down, or up. Again, ask today's consumer what the ratings on the label mean, and most of 'em have never heard of STC nor could define how the nameplate wattage is just one point on a curve.
Is this the panel manufacturer's fault? They're labeling things precisely the same as they've labeled them for 40-plus years. (Perhaps there's even more data on the panel label now, as Vmp and Imp are typically specified now, and they weren't always universal.)
Edit to add: The label doesn't typically specify the temperature coefficient, but for every panel I've checked, it is in the datasheet. But who reads datasheets?
Is it the inverter manufacturer's fault? They're labeling things precisely the same as they've labeled them for 40-plus years. The input max is a hard limit where the silicon can take no more, and there's a certain amount of headroom required between that and the panels' max, after compensating for temperature coefficient. Of course you calculate your panel voltage for your local conditions before comparing it to the inverter input, duh!
Everyone knows that! Except now they don't.
The input max is for most inverters on the market now a setpoint where they will simply disconnect, stop generating power and go into an error state that you need to hard-reset if you want to use the inverter again. It's pretty typical to have a 1000V hard limit on a nominally 800V or 600V system. If you're going to ride close to the limit then on some days you will see overvoltage and disconnects. So it is something you simply should not do. But people think that if the label says 1000V then 990V total nominal panel voltage should be fine, which it obviously is not. Panels are analog devices, they will produce an open circuit voltage much higher than their nominal use voltage and when you're on a switched mode inverter that means that the average voltage may well be 'in spec' but the voltage from one millisecond to another may well be outside of that if the system was built 'on the edge'. And because inverters have to take the grid side into account as well (they are not allowed to exceed certain voltages) there is always the risk of not being able to load the panels sufficiently to get the voltage to drop. So you should side your system so that the open loop voltage of your panels under ideal conditions is still comfortably lower than the max input voltage of the inverter. 800V nominal is pretty close to that limit, 700 is better and 600 is playing it safe.
I think one of the main reasons why installers tend to overprovision voltage wise is that they count on the inverters switching off the whole string every now and then versus being able to make more power without a lot of additional wiring under normal conditions. The net effect of that is positive.
Low quality inverters (the ones without the ability to disconnect the HV side autonomously) should be avoided like the plague anyway, those are simply unsafe and as far as I am concerned should not be allowed for re-sale at all.
My own system can make 17KW on a very good day in March at 1 pm or so, but normally it is closer to 12KW even in the summer. So those peaks are actually substantially over the normal output. Over a given day the average is about 5 KW or so from sunrise to sundown, and those first and last hours hardly contribute.
Current title is actually a subtitle. Actual title:
`Solar Panels + Cold = A Potential Problem`
The subtitle is, though, and I do find a problem with it. There might be someone out there (possibly not sober) who thinks "Magic smoke? Let's see some!" It also somewhat distorts the original. It should be more like "unless you want the magic smoke to escape." The smoke's magic properties are gone once that happens. At least, nobody has ever proven the escapee smoke has any.
To be honest I went into it half expecting it to be about papal elections[1].
[1] https://theconversation.com/conclave-the-chemistry-behind-th...
Thanks, we've updated the HN title to the article's main title now.
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Cool article. The real solution to this is have huge arrays in the desert and move the energy north, which is 100% possible.
There are a lot of possible things. The question is which is the easiest to get financing for.
I don't think that addresses the thing that the article is actually about...