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Solar panels + cold = A potential problem

linspyre.com

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Re: Solar panels + cold = A potential problem

#21

Post by mindslight »

avidiax wrote: post #10
mindslight wrote: post #3

Why does the Delta Pro not have a fuse on the input, with the MPPT limiting the max voltage to 150v (by upping the current until the voltage sags and/or the fuse blows, or even a straight crowbar circuit). This is a premium consumer brand selling a mostly complete product, and protecting the input from overvoltage would be straightforward. The frustration at the warranty weaseling isn't surprising.

You might think that the voltage rise could be too fast for most protective technologies to save the downstream electronics, but the general case is that the temperature slowly drops and the sun slowly rises. So the voltage should slowly approach the limit. Adding a normally-open relay and a voltmeter and a microcontroller should fix this. Relay won't close on startup unless the voltage is safe. Microcontroller will…

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.

Re: Solar panels + cold = A potential problem

#22

Post by quailfarmer »

Animats wrote: post #11

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-r…

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.

Re: Solar panels + cold = A potential problem

#23

Post by jonathanlydall »

therein wrote: post #4

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.

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.”

Re: Solar panels + cold = A potential problem

#24

Post by sbierwagen »

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.

Re: Solar panels + cold = A potential problem

#25

Post by teiferer »

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.

Re: Solar panels + cold = A potential problem

#26

Post by teiferer »

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…

> 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.

Re: Solar panels + cold = A potential problem

#27

Post by hathawsh »

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.

Re: Solar panels + cold = A potential problem

#28

Post by leoedin »

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.

Re: Solar panels + cold = A potential problem

#29

Post by geocar »

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.

> Not everybody buying these has a Ph.D. in physics and if it says 148 V on the label and 150 V on the other label then it's your product that has a problem, not the customer.

Idk. I don't have a PHD, but 220V sounds like 240V to me. I wouldn't do this.

I feel like getting advice about how to wire up electronics should not be so hard.

> Maybe they should just improve their product to make it more resiliant

Adding "resilience" usually adds to the per-unit cost. I think making a web page adds some cost too, but at least that can be amortised.

> And no matter what happens, customer support should help the customer, not blame them.

I think that's happening here: Making a web page to educate future customers seems like a really good idea. I wouldn't have thought that necessary until I saw it, but I'm always excited to learn something new.

The existing customers who did dumb should consider this a relatively cheap education in electronics; cheaper than a PHD at least!

Also, whether the company also gave them rebates or credits we don't know here, but telling "customer support" they "should help the customer" is also telling them they're not helping the customer, and you don't know that.

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