Solar panels + cold = A potential problem

linspyre.com

170 points by behnamoh 4 days ago


teiferer - 4 days ago

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.

Animats - 4 days ago

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.

syntaxing - 4 days ago

> 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)

franciscop - 4 days ago

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...

uyzstvqs - 4 days ago

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.

mindslight - 4 days ago

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.

nenenejej - 4 days ago

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.

cornstalks - 4 days ago

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.

dhosek - 4 days ago

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).

therein - 4 days ago

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.

bryanlarsen - 4 days ago

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...

taneq - 4 days ago

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.

nerdralph - 4 days ago

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.

jacquesm - 4 days ago

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.

gsf_emergency_2 - 4 days ago

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...

metalman - 4 days ago

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.

sowbug - 4 days ago

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.

londons_explore - 3 days ago

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.

PaulKeeble - 4 days ago

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.

bob1029 - 4 days ago

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.

hathawsh - 4 days ago

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.

mulle_nat - 4 days ago

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.

1970-01-01 - 4 days ago

>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.

sbierwagen - 4 days ago

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.

- 4 days ago
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jlundberg - 3 days ago

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).

phkahler - 4 days ago

>> 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.

BobbyTables2 - 4 days ago

Why would lower temperatures lower the maximum voltage?

Sure, diode forward voltages change a little but seems like something else is going on…

- 4 days ago
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Faaak - 4 days ago

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

jama211 - 4 days ago

Ecoflow fucked up, more news at 11.

myself248 - 4 days ago

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.

righthand - 4 days ago

Current title is actually a subtitle. Actual title:

`Solar Panels + Cold = A Potential Problem`

PortlandICEOps - 4 days ago

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Stephenbahati - 2 days ago

[flagged]

EcommerceFlow - 4 days ago

Cool article. The real solution to this is have huge arrays in the desert and move the energy north, which is 100% possible.