Bad Solar Panel

[veggie]

So, I just installed 4 x 220 watt solar panels on a rack mount system.
Somebody at the factory plugged the male and female MC-4 cables together on one of the panels.
When I took the panels out of their cardboard box on my lawn, it was a bright sunny day. Before I noticed that the one panel
was shorted out, it was too late.
3 panels put out 35 volts, 1 panel puts out ZERO.

Question.
Is this panel ruined? or is it possible that it could be repaired by opening the j-box and replacing diodes ?
At this point I have not done anything due to time constraints.

veggie

[mike90045]

A solar panel should be able to run indefinitely into a short.  That's one of the factory tests.  No diodes should be ruined.

Connecting a panel backwards can fry things, or maybe the vendor sold you a dud.

[Fred8]

I have been working in the solar game for some years now. The above poster is entirely correct.  Shorting a panels is insignificant to them.  The way they work, a dead short actually means they are generating less power through being off their Curve than under full load on it.

Wether the short caused the panel to become faulty or not, either way you were sold a dud and should return it for warranty.  Don't touch it, don't give them any opportunity to BS you by telling them it was connected when you got it, just tell them you took it out the box and it was DOA.  The only come back they could have is if the thing was shattered and as I presume it's not, they have no option but to replace it.

[BruceM]

+1
On-off type charge controllers normally use panel shorting by an N-channel Mosfet as a means of charge regulation.  IT is harmless to the panels.

You got a dud, since you're getting 0V, likely an open connection to the cells.
As Fred8 notes, report the DOA, 0V in full sun.

[veggie]

Thanks everyone for the fast replies. 

veggie

[Apply]

The issue could potentially be fixed by replacing the bypass diodes in the junction box, assuming that's where the fault lies. These components are designed to protect the panel in situations like this, so it's worth checking out. Before attempting any repairs, consult the installation manual or reach out to a professional for advice. For more detailed guides and troubleshooting tips, solargenerators.to can be a helpful resource since they have many informative articles, or you can even contact them and ask for their opinion. Just remember, working with electrical components always carries a risk, so take the necessary precautions or seek professional help if you're unsure.

[BruceM]

The bypass diodes are to provide a current path when a group of cells are shaded or have otherwise failed.  They allow the current to bypass the bad group.  A failure of a diode will not cause 0V in full sun, and in fact will have no effect unless it failed as a short, in which case voltage will be reduced, not zero.

0v is likely caused by a broken (open circuit) connection in the solar cells series connections.