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Comment by rcxdude | Hacker News Reader

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.

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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.

While in general most parts will work beyond their ratings to at least some degree, this isn't really a safety margin. A safety margin is known, rated, and validated, and usually a property of a system as opposed to just one part within it.

That’s what I said?

Usually a system would have a safety margin of at least 1.5x, or 3x or the like.

In this case the design safety margin appears to be…. 1x? Exactly?

Suspiciously so. I'd love to see somebody(or somebodies) with an established reputation reverse the controller software & hardware.

Your safety margin is my profit margin.

- Mr MBA

Your converter doesn't need to like the voltage, it just can't break from it. In fact, if it's the type that shorts the panels for curtailing, it should be happy to just run them at the highest voltage it's comfortable with, loosing a few percent generation during exceptionally cold days.

> it just can't break from it

In fact, they can.

I think they meant “it just can’t” in the sense of “it shouldn’t under any circumstances”

Even that interpretation would be be wrong because it can and it does and the circumstances are very clearly described. Every inverter worth considering for a home installation has this capability. Only really old ones are not able to disconnect from the HV side when things are about to go pear shaped. If I had an inverter without that capability I'd get rid of it immediately because that's an accident waiting to happen.

Open circuit voltage is _very much_ widely considered to be the maximum. If its not spec'd openly as " at temp X" then it's reasonable to expect it to be invariant.

"Voc 37v @ 25*C"

"Voc 37v"

Edit: Isc is the same- max current.

But that's not true - V_OC for PV modules is nearly always spec'd at STC or NOCT, which is clearly stated on module datasheets along with the temperature coefficient of that voltage.

E.g. choosing a random Jinko datasheet: https://jinkosolarcdn.shwebspace.com/uploads/JKM600-625N-66H...

V_OC is specified at both STC and NOTC, and the datasheet clearly states which environmental conditions accounted for in those test conditions.

It doesn't matter if it's true. And those spec sheets aren't what you'll find on amazon products. I looked at them, didn't see any mention of temperature. Also, stupid things use XT60 connectors. Not remotely appropriate for 150v DC.

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