Author Topic: Problem with used solar panel:  (Read 2198 times)

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billthedog

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Problem with used solar panel:
« on: March 18, 2016, 04:20:16 PM »
69 year old retired senior, live in Cali next to Yosemite National Park.  I am a electronics hobbyist and Mariposa search and rescue volunteer.
have a old 4WD truck with a bunch of old Arco (slightly browned) on the roof for camping or when I spend up to a week trying to find a lost or injured tourist in the forest.

Problem with used solar panel:

I bought a panel about 5' by 3' with 72 cells, no glass damage.

At the junction box on the back are 4 terminals, (relative to the negative
terminal) I can read 12 volts, 24 volts, and 36 volts.

But when I use a amp meter, (with or without a load in series) the meter reads zero. Tried a different meter, same thing.

Measuring across the 3 diodes in the junction box, same thing.

Good looking panel, no visable damage front or back, measurements taken
with panel in full California sun.

I am a electronics hobbyist but the has me stumped.   :-\

Bruce S

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Re: Problem with used solar panel:
« Reply #1 on: March 18, 2016, 05:01:37 PM »
When you trying to measure amps with a load how low is the battery ?

You could do a +pos to -neg short amperage test, but I don't usually do that. I use a mostly dead battery, that gives me a better amount of time to read current.

Hope this helps
Bruce S
PS>>> daughter was with Americorp out your way a short while ago. Helping out with fire rebuilds on the trials. Some of the pics she brought back were awesome!!
A kind word often goes unsaid BUT never goes unheard

OperaHouse

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Re: Problem with used solar panel:
« Reply #2 on: March 18, 2016, 05:46:54 PM »
Reading short circuit current current across each of bypass diodes is a good test. These should be for each 6 volts.  I have a couple of Photowatt panels that have died over the years.  For a while I had a good 6V section in each to give me 12V in series.  Now I get nothing from either of them.  They look to be in perfect shape, no chicken scratches or burn holes in cells.  I could easily pawn them off to someone unsuspecting based on looks.  Sometimes dead is dead.  I'll probably sell them this year to someone who needs a low iron glass and frame.

Your last chance test is to measure ohms on the diodes in the totally unlikely event something shorted them all out.

billthedog

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Re: Problem with used solar panel:
« Reply #3 on: March 19, 2016, 01:25:58 AM »
When you trying to measure amps with a load how low is the battery ?

You could do a +pos to -neg short amperage test, but I don't usually do that. I use a mostly dead battery, that gives me a better amount of time to read current.

Hope this helps
Bruce S
PS>>> daughter was with Americorp out your way a short while ago. Helping out with fire rebuilds on the trials. Some of the pics she brought back were awesome!!
I used a small car battery (almost mostly dead) this battery was at about 10.5 volts meter showed the panel was putting nothing into the battery.

dnix71

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Re: Problem with used solar panel:
« Reply #4 on: March 19, 2016, 11:03:58 AM »
Sometimes a dead battery won't take a charge. The sulfation is so bad no current will flow, at least for a few minutes. The longer you leave the panel connected the more current should begin to flow.