Solar Panel showing wrong output

[fabieville]

I have a solar panel rated for 100 Watt @ 5.1 amps and max shorted amps @ 5.5 amps.
However until recently I realize that my output has drop by about 50%. Even when the panel is facing directly at the sun and the sun is at its peak I am still not receiving the amount of amps from it when I do a current test by shorting the output leads. The most I get now is between 2.5 - 3amps.

I am guessing that a cell probably gone bad as it is a used panel and I saw like the person was trying to drill a hole in the frame but accidentally went right through and the bit went right through one of the cells and it create just a tiny little hole in the cell and looking from the backside of the panel you could see the glass which is at the front through that tiny little hole, but I dont think that small amount of gap in the cell could cause such a dramatic decrease in output. Would this have an effect on the panel like allowing moisture to develop? Or is this cell definately at fault as looking at the other cells they look quite perfect.

Another thing I was wondering if it's one or both of the diodes in the junction box gone bad?

I notice the problem just after a 2 week peroid of rain but mostly overcast was over and I did a amps test and found out the bad news.

So what do you guys think? Can it be repaired and how? I am guessing after repairing I could just use sylgard to seal it up back.

I am urgently awaiting on your reply.

[dnix71]

One ruined cell could do that much damage. Can you post a pic? If you can get at the cell to cell connecting strips and bridge past the bad cell it might restore some lost power.

[SparWeb]

Fabieville,
I'm digging up this old thread of yours because I was experimenting with repairing PV panels on the weekend.
A friend of mine has a number of bad panels, but believed that something was wrong inside the junction box.  We cut a bunch of them open together (the boxes are potted with silicone inside, making it hard to break in).
Once inside, we found that each of the under-performing panels had either disconnected wire tabs or blown diodes.
The diodes are installed between parallel strings of cells, to allow one string to keep producing even when an adjacent string is shaded, so these are called "bypass" diodes.  Not the same function as "blocking" diodes.

We replaced the diodes, re-soldered the tabs, and restored 4 panels to 100% power!

I'm writing up a diary entry, and I'll post it up soon, but I was also researching if other Fieldlines members have done the same and your question came up.
Hope it helps - only 8 years later! 

[guruji]

Sir I bought a secondhand panel too. It is giving me 34v but 1amp. It should give abiut 7amp. Opened junction box diodes on one side all blocking but checked + to - 0000 on my MM. Is this right? Cause diodes always gives a little reading. Any help please? Thks.

[SparWeb]

Hi
Here is a more detailed page that may help.

http://sparweb.ca/oldSparweb/Diary/2019_May_11.html

Yes it can be the diodes like you suspect.  It can also be the strip wires disconnected from the tabs.  They can also separate, and should be checked at the same time if you open the junction box.