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Solar panels + cold = A potential problem

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Re: Solar panels + cold = A potential problem

#81

Post by bayindirh »

amelius wrote: post #59
teiferer wrote: post #25

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.

> make it more resiliant, rather than blaming customers Yeah, this sounds very much like "you're holding it wrong".

They can add a relay, I guess? Voltage monitoring is cheap. Relays might push price above a bit, but it's a worthy premium to pay in my book.

Re: Solar panels + cold = A potential problem

#82

Post by syntaxing »

franciscop wrote: post #7

I was going to comment on the manufacturer's safety margins, but then I found a graph [1] on the variability of voltage vs temperature and it seems to be a lot steeper than I thought/expected, to the point that I'm wondering how these do not require either training or a voltage regulator to install and operate properly: https://www.researchgate.net/figure/Module-voltage-current-v...

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.

Re: Solar panels + cold = A potential problem

#83

Post by TeMPOraL »

leoedin wrote: post #28
teiferer wrote: post #25

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.

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.

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 :).

Re: Solar panels + cold = A potential problem

#84

Post by rzzzt »

gus_massa wrote: post #76
mazurnification wrote: post #66

Earlier quoted context omitted.

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)

Same thing happened to PC PSUs. I don't think there is a recent unit that still has the self-destruct voltage selector switch which pops them if you are in 230V land (and the switch is set to the smaller setting).

Re: Solar panels + cold = A potential problem

#85

Post by Faaak »

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

Re: Solar panels + cold = A potential problem

#86

Post by myself248 »

saghm wrote: post #42
syntaxing wrote: post #13

> 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.

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.

Re: Solar panels + cold = A potential problem

#87

Post by mrob »

numpad0 wrote: post #55
_9ptr wrote: post #53

Earlier quoted context omitted.

Obviously you include everything, otherwise it wouldn't be a maximum. You can define a minimum temperature for this, of course, but the customer should know about it.

There's no theoretical maximum voltages for solar panels like there kind of is for batteries. They're just giant array of photodiodes and they just generate whatever voltage potentials proportionate to amount of lights received. You could produce a "max voltage flying low earth orbit over Gobi with no shadows from Starlinks" value, but that's just the value for circumstantial most absurd situation you happened to hav…

There is a theoretical maximum: the open circuit voltage of a single photovoltaic junction cannot exceed the bandgap of the semiconductor used, no matter how much light you apply. The manufacturer knows the semiconductor used and the number of junctions in series.

Re: Solar panels + cold = A potential problem

#88

Post by phkahler »

>> 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.

Re: Solar panels + cold = A potential problem

#89

Post by crote »

sbierwagen wrote: post #24

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 on…

> 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.

Re: Solar panels + cold = A potential problem

#90

Post by geocar »

saghm wrote: post #41
geocar wrote: post #29

Earlier quoted context omitted.

> Not everybody buying these has a Ph.D. in physics and if it says 148 V on the label and 150 V on the other label then it's your product that has a problem, not the customer. Idk. I don't have a PHD, but 220V sounds like 240V to me. I wouldn't do this. I feel like getting advice about how to wire up electronics should not be so hard. > Maybe they should just improve their product to make it more resiliant Adding "re…

To me, 220 sounds 20 like lower than 240. I have a hunch that this might be a common perception.

Really?

I have all sorts of electronics that say everything from 208V - 240V that all go in the wall, so I think all those numbers are probably close to each other in whatever a volt is.

I think if I'm worried about a limit of some kind, being within 5% of that limit seems like I might as well be over-limit if the commonly seen distribution I see in my house is greater than 15%

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