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Solar panels + cold = A potential problem

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Re: Solar panels + cold = A potential problem

#161

Post by jacquesm »

dotancohen wrote: post #158
bob1029 wrote: post #153

Earlier quoted context omitted.

A capacitor wouldn't help in this case. They're most useful when you need to overcome transient situations like a locked rotor, not when you have a heavy drum that needs to be spun up from zero. During this phase the machine can consume well over 2kW of power for a few seconds. The circuit is rated for continuous 15A, but it has no problem supplying 20 or 25 for a brief period of time.

I'm sure that home mains would have no problem, but a solar installation might. Would a small li-ion help smooth over those amperage hills?

It would help at noon, when usually inverters make so much power they push the local grid to saturation which causes them to disconnect from the grid for a while. There are different rules for this for different localities, typically the installer will pick the regime appropriate for the local grid. Where I live (NL) the voltage is allowed to hit 253V for up to a minute, if it takes longer than that my inverters will switch off. That's a requirement to pass inspection, if your inverter can not do this then that's an automatic fail.

There are 'home batteries' that store power for practical reasons up to a day, maybe two. They are useful for sunny/cloudy conditions to maximize the amount of power locally consumed. But battery storage and retrieval isn't free and so far - at least, for my installation - this does not make economic sense. But another factor of two in price drop for my preferred chemistry and it definitely would make sense and then I would probably install about 20KWh worth of capacity. The trick then becomes to balance power sent to the grid and sent to the battery so that you maximize the utility of the grid in order not to wear out the battery prematurely. That means cycling the battery between 70 and 90% state-of-charge for Lithium-Ion. I'd much rather have Lithium Titanate so that is what I'll be holding out for, they are already available, but still too expensive. But they're much safer and have far better charge/discharge curves and life-span.

Re: Solar panels + cold = A potential problem

#162

Post by jacquesm »

mulle_nat wrote: post #160

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…

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.

Re: Solar panels + cold = A potential problem

#163

Post by jama211 »

cameronh90 wrote: post #148
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.

I don’t know about the components they’re selling, but with electronic components, it’s on the buyer to properly read the data sheet and understand what the quoted nominal specs mean. Unless it’s safety critical, you usually don’t want a system with a bunch of active electronics to prevent someone wiring it up wrong, because those components will interfere with whatever you’re hooking it up to, such as the MPPT, the…

This isn’t electronic components, this is sold as a consumer level gadget that anyone can use. No one expects a standard consumer to understand data sheets like that.

You started off by saying you don’t know about the components they’re selling - but that turns out to be absolutely critical to understanding the context here.

Either way, I can’t believe they just let it fry the main board instead of having a sacrificial fuse or equivalent go first in these scenarios, whether it was a product aimed at professionals or not. It’s just dumb.

Re: Solar panels + cold = A potential problem

#164

Post by Workaccount2 »

lazide wrote: post #119
rcxdude wrote: post #98

Earlier quoted context omitted.

The article presents it oddly, it's not that the converter maximum input gets lower, it's the solar panel output that gets higher from the nominal quoted value (which is not a maximum, and not really intended to be used as such). Derating your converter is equivalent for the purposes of ensuring margins, but it implies the issue is in the wrong place.

The idea of safety margins has died under the more pressing type - profit margins.

The failsafe circuit to protect against this (over voltage condition) is maybe $3 and incredibly routine in anything with power. I would bet everything that it is in there.

What's most likely though is that the fuse is also internal, and externally the unit will appear bricked.

Re: Solar panels + cold = A potential problem

#165

Post by jama211 »

hyperhello wrote: post #125
immibis wrote: post #97

Earlier quoted context omitted.

But they want you to have to buy another one.

Why does this kind of comment get downvoted that pinpoints the actual motivation? We just pretend that planned obsolescence is history.

Because it’s an extreme claim backed up with no evidence. Hanlon’s razor applies here.

Re: Solar panels + cold = A potential problem

#166

Post by jama211 »

Aurornis wrote: post #122
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…

> They shouldn't be that close to the absolute maximum voltage ratings on the components. This appears to be a situation where the engineering team determined the absolute maximum input voltage and the marketing/product people put that number straight into the documentation. Standard practice with electronic parts is to determine the absolute maximum rating, then to specify a recommended maximum that allows for some…

One way or another, many of us are in agreement the company screwed up and it’s on them to fix it - whether that’s their marketing, their manual, their lack of over voltage protection, whatever it is it’s their fault.

Yet so many people in this thread are so keen to blame the customer, it’s pure ego from them. “I’m too smart for that to happen, so it’s all their fault!” they sneer. Classic bad faith forum behaviour…

Re: Solar panels + cold = A potential problem

#167

Post by mschuster91 »

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.

Maybe it would be a good idea to at least add a pair of MOSFETs (one for each rail, + and -) and a voltage meter? Like, the voltage doesn't rise to maximum instantaneously, there should be ample of time to detect voltage rising to a critical amount.

So say, the input is rated for 150V, spec the components to sustain 180V, and trigger the MOSFETs to disconnect the panels at > 160V.

And maybe also add a big ass buffer capacitor, that can be used to soak up a bit more energy in the case of an inrush spike before the MOSFETs actually disconnect.

Re: Solar panels + cold = A potential problem

#168

Post by jama211 »

jfengel wrote: post #105
Jgrubb wrote: post #102

Earlier quoted context omitted.

I love a good analogy. This is not a good analogy.

I'm not sure I know what a good analogy looks like. If the two things are identical, then the analogy is uninformative. If they're at all different, you will zero in on the differences rather than the similarities. Sometimes they can be ok pedagogical tools, but they're easily misused as tools of persuasion.

You’re not supposed to zero in on the ways in which an analogy doesn’t apply. You’re simply supposed to read the analogy in order to see what it’s attempting to _highlight_ about the scenario.

This is a common pet peeve of mine, people not understanding how analogies are supposed to work and getting distracted by the differences. They’re supposed to work like a light filter placed over a lens, something will be highlighted and focus on that, don’t focus on the fact that “but all the colours are different now!”, the only purpose of using the light filter was to highlight a specific part of the image, the fact that it also coloured everything wrong temporarily is supposed to be ignored.

You know, just to use an analogy to explain analogies. Gotta be as meta as possible.

Re: Solar panels + cold = A potential problem

#170

Post by Workaccount2 »

beefnugs wrote: post #51
xg15 wrote: 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…

This is what makes software engineering so seductive, everything works exactly as it was designed to (whether intended or not). Imagine trying to program for computers with memory that drifts values progressively more as it wears down.
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