Check solar panel amp output with a battery tester with a 50 amp load?

[Outbackman1]

I tested the amperage output on some used Kyocera 120 watt panels with a 10 amp test on a multimeter and got varying outputs ranging from 2 to 5 amps. I recently tested them with a brief 50 amp load and they all tested 7 amps and over. This is in direct Arizona Outback 100 degree sun. I tested several new panels the same way and they all tested equal to or above specs. Is this an accurate way to test panels? I fried the amp test function on a couple of cheapish multimeters so thought I would try a different approach with the battery load tester.

[bob-n]

Output current varies with load like in the plot below (note: this is a plot of one cell. Your panel has many cells, depending on the model, but definitely much higher total voltage). If you just use an ammeter and no load, you are measuring short circuit current. I'm not sure what was in your 50 amp load, but it was probably very low resistance, so close to short circuit. To find out what your panel can really do, you need something like a high-power variable resistor and increase the resistance until you get near the maximum power point. Then multiple current x voltage and see how many watts you get.

Solar-panel-output-voltage-current-and-power.jpg

[Outbackman1]

Well my testing wasn't accurate. As soon as I hooked the panels into my system they didn't produce much amperage. You were right in your assumption.