Solar Panel Voltage Drops to Zero

[Sergy]

Hi Everyone
I was on the boat this weekend and I noticed one bank of 2 45Watt solar panel was producing “0” volts on sunny day then it would come back on at 15.6 volts and when it would reach 16 volts every thing went to zero. My first thought was a poor connection or faulty wire but then I remembered there was some sort of regulator on bottom of panels with diode. I wonder if this is a voltage limiter and drops voltage to 0 when above 16 volts any ideas would be appreciated. The second bank next to it was supplying 16 plus and still kept on trucking

[cdennyb]

the diode(s) is probably a "blocking diode". I have them on my panels and they prevent a backflow of voltage from your batteries to the PVpanel when the light drops below the threshold to make charging power. It sounds like a thermal break in the crystalline plates or something similiar. I have seen them develop disconnects due to the heat. I might be wrong about yours but I'm not there to check them mysef. Hope this helps.

[Sergy]

Thanks for the reply this could be the problem. I don't expect this is somthing you repair??

[cdennyb]

Unfortunately... you are correct. they aren't really repairable but... if you recently purchased these, like in the last year or so... the mfg may take a look at it and replace it for you. It never hurts to ask. After all... they can't really afford the "bad publicity" among cruisers which account for a significant portion of their marine business. I'd check with a local dealer first... ask some good questions, then take the offending unit in for a checkup. They could be your best friend when dealing with the factory.
If that fails, there's always the internet and you can find the customer service person to help you. Maybe at the very least you'll get a pro-rated discount on the purchase of the replacment unit.
Sorry the damn thing quit you. Better at the dock than 300 miles out.

Hey: Here's a test you can do. Get that thing in direct sunlight like it is when it fails and throw some water on the panel to chill it to keep it cool and see ifit still does that. If it quits, then you're on to the logical reason for it's failure... thermally related expansion and probably trace breakage.

db

[Sergy]

Hi Dan
Thanks for your advice
I have considered your deduction and have come up with a possible wire problem instead see if this makes sense. (These unit are old by the way.).
I have 4 units in all 2 banks of 2 (45 watt each) Each bank has 2 units connected in parallel.
When the voltage drops to 0 on the troubled bank if your deduction were correct and one of the 2 panels was defective because of heat then the 2ed unit should still be putting out 16 volts unless the first was causing a short which the blocking diode should stop or 2 panels suffering from the same problem. (could have been running on only one panel for some time)
By the way when this happened I sprayed with Windex to clean the top no difference but would of cooled then I tightened the wires with intermittent results and when I left all was working the next day when it was cloudy.