How Do You Recognize A Bad Panel Diode?

[SamirD]

I have an enphase system that was installed in 2016 before I bought the home in 2022. It works well except for one panel that seems to be producing less power than adjacent panels in the same conditions. I looked back at the data on the panel all the way to the install date and it used to produce the same as the others. And then about 10 days in, it was intermittently doing the same and then less, and then starting doing less and has ever since.

After reading some threads on the enphase community, it appears this could be a 'bad diode' in that particular panel. And depending on how many diodes are in the panel, the loss would be proportional--33%/66% for a 3-diode, 50% for a 2, etc.
Does this fall in line with what the community here thinks? Or is there a different theory? Happy to hear feedback.

[bcroe]

Experience here with a weak panel has been, one of the 3 sections of cells
strung in series cannot maintain the same current as the others. So the
voltage output of that section will collapse and full curent from the other
sections will be maintained thru the bypass diode. The situation may come
and go depending on sun intensity, and other panels in series with that one.

No bypass diodes have been seen failed here so far. They are under little
stress, until used to bypass a weak section. Bruce Roe

[SamirD]

Thank you for the detailed feedback Bruce! So it could also be that a particular section of that panel is bad, right?

[solarix]

Panel bypass diodes usually fail short causing the panel's voltage to be only about 2/3 of normal. Had a customer's pole mounted array get hit by lightning and many of the diodes were shorted.

[bcroe]

Panel bypass diodes usually fail short causing the panels voltage to be only about 2/3 of normal. Had a customer's pole mounted array get hit by lightning and many of the diodes were shorted.

All bets are off with lightning. Nothing taking a direct hit here so far,
have had electronic damage in the past from a close by strike. Bruce Roe

[SamirD]

Panel bypass diodes usually fail short causing the panels voltage to be only about 2/3 of normal. Had a customer's pole mounted array get hit by lightning and many of the diodes were shorted.

Yep, sounds like that's what I've got going on and it was a 'doa' type of thing since it did it 10 days after install.

[SamirD]

So the question is how does a warranty typically address this? If there even is a warranty anymore for a system installed by Petersen Dean.