Verifying panel performance before installation

Re: Verifying panel performance before installation

Three basic tests to see if panels are, roughly, OK...

1. Voc--open circuit voltage test. Just throw the panel in full sun and measure voltage
2. Isc--short circuit current test. Set your DVM to 10 amp full scale and short across the panel output (it is OK to short the panels). Put panel in full sun and measure current (which will pretty much be porportional to the strength of the sun light). You can compare with another panel--if you have one.
3. Properly connect your panel to a 12 volt car battery and measure current output in full sun.

#1 and #2 will pretty much weed out ~90% of the good panels.

#3 will find the few bad panels that have failed in certain ways that 1&2 may not.

If you are looking for panels that are outside the spec. range (10-20% out)--that is much more difficult without a pyrometer and specialized lighting.

If you do tests #2 and/or #3 with a known good panel and immediately flip over to the DUT (device under test--or use a second DVM)--you should be able to scale for variable solar output and find a "weak" panel. Remember, Vmp and Voc are temperature dependent--so you need to have both panels at the same temperature for accurate measurements (with better than 5-10% accuracy).

Also--if you have some need to test a lot of panels--I would be tempted to use a pair of small MPPT controllers to compare Ref/DUT panels into a known load (battery with load or something similar). Those would do a very good job of giving you accurate Vmp/Imp for yoru panels--but probably way overkill for the average person.

-Bill