I done a bad thing: need advice diagnosing shorted PV panel (output = half voltage)

MetroMPG · 04-11-09, 03:30 PM

Play with fire and you get burned...

Play with a nice commercial PV panel & batteries without taking the time to put a fuse inline first ... and you'll eventually screw up by reversing polarity to the batteries and frying your panel.

The panel is a new Sharp NE80EAEJ - 80w module, 21.6 open circuit voltage. Got it relatively inexpensively on eBay because the frame was damaged after manufacturing, but the cells & glass were still OK.

So enough back story. Here's how I SNAFU'd it:

This afternoon I mistakenly hooked it up BACKWARDS (reverse polarity) to a nearly fully charged 12v battery and the instant I connected the lead I knew I done a bad thing from the size of the arc.

Now the panel is putting out exactly half its rated voltage. Fine. So I guess I blew out a connection somewhere between the two strings of cells, right?

I identified which string seemed to be isolated, and dug the potting material out of the junction box (see photo) and found what looked like a "blown" connection. After cleaning the material out and soldering it back together I now have ZERO volts output.

So I disconnected the join and I'm back to half panel voltage. And... now I'm a little confused.

I should add: the blown out connection seemed like it may have had some crumbly material in it between the copper traces - maybe silicon wafer? Was it maybe a diode?

Any ideas for me?

(I'll be away this evening - will reply tomorrow or later tonight if anyone has any suggestions or questions....)

04-11-09, 03:30 PM	#1
MetroMPG Infrequent noob Join Date: Aug 2008 Location: 1000 Islands region, Ontario, Canada Posts: 402 Thanks: 37 Thanked 20 Times in 19 Posts	I done a bad thing: need advice diagnosing shorted PV panel (output = half voltage) Play with fire and you get burned... Play with a nice commercial PV panel & batteries without taking the time to put a fuse inline first ... and you'll eventually screw up by reversing polarity to the batteries and frying your panel. The panel is a new Sharp NE80EAEJ - 80w module, 21.6 open circuit voltage. Got it relatively inexpensively on eBay because the frame was damaged after manufacturing, but the cells & glass were still OK. So enough back story. Here's how I SNAFU'd it: This afternoon I mistakenly hooked it up BACKWARDS (reverse polarity) to a nearly fully charged 12v battery and the instant I connected the lead I knew I done a bad thing from the size of the arc. Now the panel is putting out exactly half its rated voltage. Fine. So I guess I blew out a connection somewhere between the two strings of cells, right? I identified which string seemed to be isolated, and dug the potting material out of the junction box (see photo) and found what looked like a "blown" connection. After cleaning the material out and soldering it back together I now have ZERO volts output. So I disconnected the join and I'm back to half panel voltage. And... now I'm a little confused. I should add: the blown out connection seemed like it may have had some crumbly material in it between the copper traces - maybe silicon wafer? Was it maybe a diode? Any ideas for me? (I'll be away this evening - will reply tomorrow or later tonight if anyone has any suggestions or questions....) Attached Thumbnails __________________ . To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.