Solar mystery

[sneuman]

Helping a friend in trying to diagnose a problem with his approximately 250watt solar array on an Ericson 38.

Suddenly, he's getting good voltage but almost no amperage out of the panels on a sunny day (about .5amps when he used to get 4-5amps). Suspected the charge controller, but that seems to functioning OK (checked with an multimeter). The panels are perhaps 10 years old (they came with the boat when he bought it 5 years ago), but it would, in any case, seem odd that all three panels would simultaneous pass their due date.

Coincidentally (or maybe not), the apparent failure of the solar grid closely follows an inexplicable overcharging of the batteries, which I initially thought might be the result of a bad charge controller.

Any thoughts before we call a professional?

[Cotemar]

1) Disconnect each panel
2) Check each panels output with voltmeter
3) Is each panel putting out the spec. output
4) If yes to 3) then check all other wiring and fuses to the controller.
5) Break down every thing into small steps
6) Panels for step one,
7) Wiring and fuses for step two
8) Controller for step three
9) Your multimeter will be your best friend, Use both Voltage & continuity tests.

[senormechanico]

Sounds like a high resistance connection somewhere.
Are the panels in series or parallel?
If parallel connected, disconnect the panel array from the controller and with an ammeter capable of measuring up to 20 amps, connect it directly across the + and - terminals of the panel array.
Alternatively, if you don't have a meter with that capacity, you can check each panel individually in the same manner.
If they all put out approximately the same amount, move on to temporarily bypassing the controller to see if you get decent current.

Hee hee! same response at the same time!

[hellosailor]

If these are '12" volt panels with a 12 volt battery system? Id disconnect the charge controller and separate the panels. Then check battery voltage, make sure they are not at 100% charge, discharge them if need be. Guessing to the 60-80% charge depth.

Now take each panel, one at a time. Connect directly to the battery with an ammeter in line, and see what the panel is putting out. Check again to see what voltage is it putting out, under load to the battery. (Faster if you have two meters.)

If each panel tests OK by itself, as I suspect they will, then the charge controller is the problem. If the batteries overcharged and that controller is their only charging source--that's a finger pointing to the controller as well.

I suppose it is possible, depending on what was connected and how, that a diode failed, the panels took too much reverse current, and some cells burned out ruining all of them. But that kinda seems way less likely.

Divide and conquer, get the charge controller physically OUT of the picture and see how the other kids play without it.

[GeoPowers]

Agree with check the obvious in connections and output with multimeter. Then depending on the Voc of the array (or of each panel), I'd bypass the charge controller and hook directly to the house bank and see what it is putting out.

I see hellosailor and I were typing at the same time!

[hellosailor]

Depending on the type of controller (dare I suspect MPPT?) you never know what games it is playing with the solar panels. And not knowing what it might be doing, that's why I suggest pulling it and just starting with testing the panel output to a hungry battery. KISS.

[sneuman]

Thanks all. We took advice here and bypassed the controller this weekend and discovered we were getting 10amps directly from the panels. So, that solves it - it's indeed the controller!