Tuesday, Apr 16, 2013 at 22:27
The answers above are mostly too detailed and confusing.
To measure the output from a solar panel do this:
Disconnect both leads of the panel from any controller, battery or any other van wiring.
Take your multimeter, set at a suitable voltage range and measure what's coming out at the two wires, making sure your panel receives sunlight of course.
With a digital multi meter it does not matter which meter lead goes to which wire, the meter just displays a negative reading if its reverse connected.
There should be between 18 & 21 volts for a 12V nominal panel, depending on how many cells the panel has.
Next, and this might worry some people, it is quite OK to short circuit a single solar panel by itself (its not connected to anything else). The max current (Amps) that can flow is what's shown on the label under short circuit current.
Just set the multimeter to the 10A DC range, assuming the panel has less than 10A sc rating. Connect the meter probes to each wire of the panel, this is the same as short circuiting the panel BTW, and measure the short circuit current.
It should be close to the spec on the label but is dependent on the amount of sunlight. If it shows a healthy Amp reading the panel is fine and you can eliminate it from the cause of your problem.
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