Panel damage

[sdold]

Does this look like lightning damage? The front side is brown and discolored, but the glass is intact. Burning is evident on the back side. It's a Siemons SM-110 "12V" panel, part of a four-panel series string that paralleled with seven similar strings. It's a high mountain site so lightning is common here.

[emartin00]

I would guess some type of internal short.
Lightning would likely have destroyed the whole panel, not just fried one cell.

I suppose it could be an indirect strike which would induce a high voltage in the system.

[Mike90250]

Looks like limited failure of just couple spots, Lightning/EMP should have zippered the whole panel like that, not just 1 cell.

What is the string voltage ?

[sdold]

I thought so too, but haven't seen lightning damage to panels It's one in a series string of four, for a 48 volt system. I'm guessing around 75V when the on/off charging relays are off. I have air terminals all over the array and don't see any blackening of frames or anything else. I guess I'll have to go up and look closer all over the array to see if I see any gaps jumped or anything like that. I've just never seen anything like this.

[solar pete]

It's looks like a hot spot to me caused by many years of the panel being shaded from fixed objects on the roof, I see it all the time.

[sdold]

Thanks Pete, it's not shaded. Also I was mistaken about the configuration, this panel is in a 12V system (the site has 12 and 48). It's paralleled with six others, and then that group is repeated four times for a total of 28 panels in parallel in the 12V section. Could it be that the other panels shoved some current through a defect in this panel? The panel is on the bottom row, fifth from the far right. The drawing shows the interconnect, one of a group of four. There are no fuses in the paralleled panels as you can see.