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Solar panels + cold = A potential problem

linspyre.com

71–80 of 228 posts

Re: Solar panels + cold = A potential problem

#71
post #42

> 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…

Agreed. No one needs to change which type of gas they use because it happens to be a warm sunny day.

In the Corvette community, using a higher octane fuel on hotter days is well known to prevent ping.

Re: Solar panels + cold = A potential problem

#72
post #55

Earlier quoted context omitted.

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 hav…

So it is doubly important that all equipment downstream has overvoltage protection? In fact considering there is no theoretical maximum, it would be downright negligent not to have overvoltage protection

Yeah, billowing magic smoke just sounds wrong. No disagreement there.

Re: Solar panels + cold = A potential problem

#73
post #35

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.

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.

Re: Solar panels + cold = A potential problem

#74
post #46

Earlier quoted context omitted.

This feels a bit like the logic behind "do not put hamster in microwave" warning labels. I think if you work with electrical or electronic systems in practice, you learn pretty quickly to respect tolerances and that data sheets are a map, not the territory. Also, electrical installations are usually seen as a field that should be done by trained personnel, not arbitrary laymen home owners. So I think the appropriate…

Actually if "you work with electrical or electronic systems in practice" you get pissed off at everything for how dumb it all is: 12V DC batteries are more like 14 nominal? AC wall plugs dip voltage when printers turn on, random equipment you arent even sure in the building can trigger UPSes based on unknown settings in the device? International standards and communication protocols mean nothing as "a standard" becau…

The modern engineer:

It works! OK, stop touching it. We don't want to break it.

Re: Solar panels + cold = A potential problem

#75

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…

All solar panel datasheet have temp coefficient, eg for one random ecoflow solar panel:

   Temperature Coefficient Specifications
   TKPower -(0.39±0.02)%/k
   TKVoltage -(0.33±0.03)%/k
   TKCurrent +(0.06±0.015)%/k
source https://websiteoss.ecoflow.com/cms/upload/2022/10/15/-139121...

STC ("standard testing conditions" for solar panels) is 25C so if it's freezing 0C you have 25 multiplied by 0.33 Volt = 8.25 Volt more than STC in open circuit situation.

Unfortunately inverter manufacturers seldom document how many Volt will destroy the MPPT and up to how many Volt the MPPT will safely turn off by itself before breaking.

Re: Solar panels + cold = A potential problem

#76
post #58

Earlier quoted context omitted.

> Idk. I don't have a PHD, but 220V sounds like 240V to me. I wouldn't do this. 220[Vrms] * 1.414 = 311[Vp-p] btw. HOW!?

So the issue is that 220V is nominal in China, 230V nominal in UE and 240V is UK/part of Australia. So if anyone is preparing product for global market (as most are doing now) more likely then not will support all of this voltages. Thus is kind of normal (but wrong) to assume 220V sounds like 240V.

Many charguers are now 100-240V, 50-60Hz, that is close to pluggable anywhere on Earth. (I burned one or two a long time ago, when I forgot to check and used a 120V transformed here with 220V)

Re: Solar panels + cold = A potential problem

#77
post #37

Earlier quoted context omitted.

High voltage, low RDSON FETs are (slightly) more expensive, and these products are cheap. A better design would use a higher-voltage rated input switch with poor (slow) switching performance, like an IGBT. Don’t design critical infrastructure around EcoFlow hardware.

Fujitsu, which sells MOSFETs for this application, writes: "Firstly devices should be rated at 600V or 650V, as this will generally provide more than adequate protection against the threat of high voltage transients."[1] That's a nice big safety margin. It should hold until the voltage monitoring shuts the whole thing off. Not seeing UL certification on this thing. If we're going to have US protectionism against Chin…

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.

Re: Solar panels + cold = A potential problem

#78
post #12

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).

There are also power optimizers which are DC-DC and connected in series.

Re: Solar panels + cold = A potential problem

#79
post #60

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.

I read it as a problem with solar panel voltage going over declared threshold of 37v in certain meteo conditions. That is the issue is with the wrong labeling of things that are being plugged into this vendor's device, not the vendor's own labeling.

If something can go wrong, it will go wrong. So both parties should note that something can go wrong and point to that something.

Re: Solar panels + cold = A potential problem

#80
post #60

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.

I read it as a problem with solar panel voltage going over declared threshold of 37v in certain meteo conditions. That is the issue is with the wrong labeling of things that are being plugged into this vendor's device, not the vendor's own labeling.

I believe the vendor here produces both the device and the panels being plugged into it, and while they also supply other vendors' panels, they seem concerned primarily with customers who buy all components from them and then experience this failure.

I agree the labeling is an issue here, but the solution must come from the wider industry or regulatory bodies; the alternative is for vendors to switch to their own pseudo-units to internalize the math, which would not be good for customers either - think "ACME Generator2000 accepts up to 4 Power Units of input; each ACME SuperEco Panel supplies 1 Power Unit, or 1.5 Power Units if you're in Canada...".

Saving users from having to do a little thinking to not brick their device is a tried-and-true excuse for vendor lock-in in our industry :).

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