12 ms·

Solar panels + cold = A potential problem

172 points by behnamoh 1y ago

BobbyTables2 1y ago
Why would lower temperatures lower the maximum voltage? Sure, diode forward voltages change a little but seems like something else is going on…
- AgentK20 1y ago
  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.
- mindslight 1y ago
  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)
- bobjordan 1y ago
  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.
- objectcode 1y ago
  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...
- namibj 1y ago
  It's not that little given these diodes run between sun baked summer and cold soaked winter dawn.
mindslight 1y 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.
- avidiax 1y ago
  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.
  - mindslight 1y ago
    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.
  - namibj 1y ago
    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.
therein 1y 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.
- setterle 1y ago
  It's the soul leaving the IC.
- dgfitz 1y ago
  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.
  - ggm 1y ago
    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.
  - ramses0 1y ago
    Hackers dictionary: http://www.catb.org/jargon/html/M/magic-smoke.html http://www.catb.org/jargon/html/M/magic-smoke.html
- jonathanlydall 1y ago
  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.”
franciscop 1y 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-vs-temperature_fig7_282755961 https://www.researchgate.net/figure/Module-voltage-current-v...
- fake-name 1y ago
  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 https://en.wikipedia.org/wiki/Maximum_power_point_tracking )
  - childintime 1y ago
    Note it would be sufficient to shut down (short-circuit) a single panel, which is safe, to lower the overall voltage.
- syntaxing 1y ago
  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.
Animats 1y 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.
- quailfarmer 1y ago
  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.
  - Animats 1y ago
    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-development/innovationcentre/articles/tcm0208_mosfet.html https://toshiba.semicon-storage.com/eu/semiconductor/design-...
    - adrian_b 1y ago
      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.
dhosek 1y 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).
- NooneAtAll3 1y ago
  you might be misremembering bypass diodes?
  - ianlevesque 1y ago
    No, microinverters are still a thing (Enphase is a popular brand) and they do then get connected in parallel.
- baq 1y ago
  There are also power optimizers which are DC-DC and connected in series.
- namibj 1y ago
  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.
syntaxing 1y 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)
- saghm 1y ago
  Agreed. No one needs to change which type of gas they use because it happens to be a warm sunny day.
  - dotancohen 1y ago
    In the Corvette community, using a higher octane fuel on hotter days is well known to prevent ping.
    - jfengel 1y ago
      I'm surprised the Vette doesn't call for high octane all the time. It's common for high compression engines.
      - dotancohen 1y ago
        The knock sensor on LT1 and later engines allows one to get away with lower octane fuel for day to day driving.
  - myself248 1y ago
    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.
deleted 1y ago
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nenenejej 1y 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.
- unglaublich 1y ago
  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...
  - necovek 1y ago
    [flagged]
  - necovek 1y ago
    Quote from the internet in reference to 10mm2 wire gauge: "This metric wire size is common in industrial settings for high-power devices and main circuits where thicker conductors are needed for safety and efficiency." That would be quite some oven.
- maccard 1y ago
  > 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.
- Aurornis 1y ago
  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.
sbierwagen 1y 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.
- teiferer 1y ago
  > 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.
  - Dylan16807 1y ago
    You think ecoflow is responsible for this website and is pretending not to be?
- BertoldVdb 1y ago
  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.
- crote 1y ago
  > 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.
teiferer 1y 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.
- leoedin 1y ago
  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.
  - cornholio 1y ago
    Panels are not standardized and are themselves series-parallel constructions with wildly diverse specs.
  - TeMPOraL 1y ago
    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 :).
    - namibj 1y ago
      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.
hathawsh 1y 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.
righthand 1y ago
Current title is actually a subtitle. Actual title: `Solar Panels + Cold = A Potential Problem`
- marginalia_nu 1y ago
  To be honest I went into it half expecting it to be about papal elections[1]. [1] https://theconversation.com/conclave-the-chemistry-behind-the-black-and-white-smoke-255980 https://theconversation.com/conclave-the-chemistry-behind-th...
- tgv 1y ago
  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.
- tomhow 1y ago
  Thanks, we've updated the HN title to the article's main title now.
bob1029 1y 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.
- dotancohen 1y ago
  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.
  - deleted 1y ago
    [deleted]
  - namibj 1y ago
    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.
    - dotancohen 1y ago
      Do any home battery systems, or home appliances, actually support this?
      - namibj 1y ago
        Most electronic power supplies for computers and similar devices (like e.g. modern TV) have zero complaints about being fed such DC. Sadly only those that try to sell to Alirack applications (i.e., Chinese server PSU's like for example Lenovo Servers) bother testing in QA and doing enough design review to officially claim that support on their data plate. You can tear down a sacrifice from a series of identical consumer PSUs though, and reverse engineer the front end schematic to check that the AC side of the active power factor correction design that you'd find in e.g. a decent gaming PSU doesn't do anything that would react badly to a lack of AC.
uyzstvqs 1y 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.
- taneq 1y ago
  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)?
  - _9ptr 1y ago
    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.
    - numpad0 1y ago
      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.
      - jimnotgym 1y ago
        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
taneq 1y 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.
deleted 1y ago
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gsf_emergency_2 1y 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/S2589004224000270 https://www.sciencedirect.com/science/article/pii/S258900422... https://www.pv-magazine.com/2025/01/13/daytime-radiative-cooling-tech-for-solar-panels/ https://www.pv-magazine.com/2025/01/13/daytime-radiative-coo...
- pfdietz 1y ago
  https://web.stanford.edu/group/fan/publication/Li_ACSPhotonics_4_774_2017.pdf https://web.stanford.edu/group/fan/publication/Li_ACSPhotoni...
  - gsf_emergency_2 1y ago
    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 https://www.nature.com/articles/nature13883 Maybe comparable cooling can be achieved with even cheaper techniques..?
    - pfdietz 1y ago
      The interesting implication is that PV has more upside growth potential than nuclear, against the ultimate limit of global thermal pollution.
Faaak 1y 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
- namibj 1y ago
  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?
  - Faaak 1y ago
    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 ;-)
phkahler 1y 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.
myself248 1y 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.
- jacquesm 1y ago
  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.
metalman 1y 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.
bryanlarsen 1y 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-vertical-solar-panels-shine-in-norway/ https://cleantechnica.com/2025/09/27/bifacial-rooftop-vertic...
sowbug 1y 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.
- namibj 1y ago
  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.)
EcommerceFlow 1y ago
Cool article. The real solution to this is have huge arrays in the desert and move the energy north, which is 100% possible.
- adrianN 1y ago
  There are a lot of possible things. The question is which is the easiest to get financing for.
- phyzome 1y ago
  I don't think that addresses the thing that the article is actually about...
cornstalks 1y 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.
1970-01-01 1y 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.
- stockresearcher 1y ago
  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.
nerdralph 1y 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.
PaulKeeble 1y 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.
PortlandICEOps 1y ago
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jacquesm 1y 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.
mulle_nat 1y 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.
- jacquesm 1y ago
  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.
- Chilko 1y ago
  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.
jama211 1y ago
Ecoflow fucked up, more news at 11.
jlundberg 1y 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).
londons_explore 1y 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.
- londons_explore 1y ago
  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.
  - hyghjiyhu 1y ago
    Chemical batteries naturally supply a fixed voltage. You can have a fixed voltage over an open circuit without losing energy.
Stephenbahati 1y ago
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Kate5477 1y ago
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172 points by behnamoh 1y ago

Why would lower temperatures lower the maximum voltage? Sure, diode forward voltages change a little but seems like something else is going on…

AgentK20 1y ago
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.
mindslight 1y ago
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)
bobjordan 1y ago
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.
objectcode 1y ago
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...
namibj 1y ago
It's not that little given these diodes run between sun baked summer and cold soaked winter dawn.

mindslight 1y 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.

avidiax 1y ago
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.
- mindslight 1y ago
  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.
- namibj 1y ago
  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.

therein 1y 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.

setterle 1y ago
It's the soul leaving the IC.
dgfitz 1y ago
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.
- ggm 1y ago
  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.
- ramses0 1y ago
  Hackers dictionary: http://www.catb.org/jargon/html/M/magic-smoke.html http://www.catb.org/jargon/html/M/magic-smoke.html
jonathanlydall 1y ago
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.”

franciscop 1y 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-vs-temperature_fig7_282755961 https://www.researchgate.net/figure/Module-voltage-current-v...

fake-name 1y ago
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 https://en.wikipedia.org/wiki/Maximum_power_point_tracking )
- childintime 1y ago
  Note it would be sufficient to shut down (short-circuit) a single panel, which is safe, to lower the overall voltage.
syntaxing 1y ago
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.

Animats 1y 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.

quailfarmer 1y ago
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.
- Animats 1y ago
  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-development/innovationcentre/articles/tcm0208_mosfet.html https://toshiba.semicon-storage.com/eu/semiconductor/design-...
  - adrian_b 1y ago
    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.

dhosek 1y 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).

NooneAtAll3 1y ago
you might be misremembering bypass diodes?
- ianlevesque 1y ago
  No, microinverters are still a thing (Enphase is a popular brand) and they do then get connected in parallel.
baq 1y ago
There are also power optimizers which are DC-DC and connected in series.
namibj 1y ago
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.

syntaxing 1y 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)

saghm 1y ago
Agreed. No one needs to change which type of gas they use because it happens to be a warm sunny day.
- dotancohen 1y ago
  In the Corvette community, using a higher octane fuel on hotter days is well known to prevent ping.
  - jfengel 1y ago
    I'm surprised the Vette doesn't call for high octane all the time. It's common for high compression engines.
    - dotancohen 1y ago
      The knock sensor on LT1 and later engines allows one to get away with lower octane fuel for day to day driving.
- myself248 1y ago
  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.

deleted 1y ago

[deleted]

nenenejej 1y 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.

unglaublich 1y ago
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...
- necovek 1y ago
  [flagged]
- necovek 1y ago
  Quote from the internet in reference to 10mm2 wire gauge: "This metric wire size is common in industrial settings for high-power devices and main circuits where thicker conductors are needed for safety and efficiency." That would be quite some oven.
maccard 1y ago
> 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.
Aurornis 1y ago
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.

sbierwagen 1y 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.

teiferer 1y ago
> 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.
- Dylan16807 1y ago
  You think ecoflow is responsible for this website and is pretending not to be?
BertoldVdb 1y ago
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.
crote 1y ago
> 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.

teiferer 1y 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.

leoedin 1y ago
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.
- cornholio 1y ago
  Panels are not standardized and are themselves series-parallel constructions with wildly diverse specs.
- TeMPOraL 1y ago
  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 :).
  - namibj 1y ago
    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.

hathawsh 1y 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.

righthand 1y ago

Current title is actually a subtitle. Actual title: `Solar Panels + Cold = A Potential Problem`

marginalia_nu 1y ago
To be honest I went into it half expecting it to be about papal elections[1]. [1] https://theconversation.com/conclave-the-chemistry-behind-the-black-and-white-smoke-255980 https://theconversation.com/conclave-the-chemistry-behind-th...
tgv 1y ago
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.
tomhow 1y ago
Thanks, we've updated the HN title to the article's main title now.

bob1029 1y 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.

dotancohen 1y ago
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.
- deleted 1y ago
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- namibj 1y ago
  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.
  - dotancohen 1y ago
    Do any home battery systems, or home appliances, actually support this?
    - namibj 1y ago
      Most electronic power supplies for computers and similar devices (like e.g. modern TV) have zero complaints about being fed such DC. Sadly only those that try to sell to Alirack applications (i.e., Chinese server PSU's like for example Lenovo Servers) bother testing in QA and doing enough design review to officially claim that support on their data plate. You can tear down a sacrifice from a series of identical consumer PSUs though, and reverse engineer the front end schematic to check that the AC side of the active power factor correction design that you'd find in e.g. a decent gaming PSU doesn't do anything that would react badly to a lack of AC.

uyzstvqs 1y 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.

taneq 1y ago
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)?
- _9ptr 1y ago
  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.
  - numpad0 1y ago
    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.
    - jimnotgym 1y ago
      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

taneq 1y 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.

deleted 1y ago

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gsf_emergency_2 1y 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/S2589004224000270 https://www.sciencedirect.com/science/article/pii/S258900422... https://www.pv-magazine.com/2025/01/13/daytime-radiative-cooling-tech-for-solar-panels/ https://www.pv-magazine.com/2025/01/13/daytime-radiative-coo...

pfdietz 1y ago
https://web.stanford.edu/group/fan/publication/Li_ACSPhotonics_4_774_2017.pdf https://web.stanford.edu/group/fan/publication/Li_ACSPhotoni...
- gsf_emergency_2 1y ago
  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 https://www.nature.com/articles/nature13883 Maybe comparable cooling can be achieved with even cheaper techniques..?
  - pfdietz 1y ago
    The interesting implication is that PV has more upside growth potential than nuclear, against the ultimate limit of global thermal pollution.

Faaak 1y 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

namibj 1y ago
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?
- Faaak 1y ago
  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 ;-)

phkahler 1y 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.

myself248 1y 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.

jacquesm 1y ago
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.

metalman 1y 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.

bryanlarsen 1y 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-vertical-solar-panels-shine-in-norway/ https://cleantechnica.com/2025/09/27/bifacial-rooftop-vertic...

sowbug 1y 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.

namibj 1y ago
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.)

EcommerceFlow 1y ago

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

adrianN 1y ago
There are a lot of possible things. The question is which is the easiest to get financing for.
phyzome 1y ago
I don't think that addresses the thing that the article is actually about...

cornstalks 1y 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.

1970-01-01 1y 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.

stockresearcher 1y ago
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.

nerdralph 1y 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.

PaulKeeble 1y 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.

PortlandICEOps 1y ago

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jacquesm 1y 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.

mulle_nat 1y 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.

jacquesm 1y ago
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.
Chilko 1y ago
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.

jama211 1y ago

Ecoflow fucked up, more news at 11.

jlundberg 1y 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).

londons_explore 1y 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.

londons_explore 1y ago
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.
- hyghjiyhu 1y ago
  Chemical batteries naturally supply a fixed voltage. You can have a fixed voltage over an open circuit without losing energy.

Stephenbahati 1y ago

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Kate5477 1y ago

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