Solar Panel Spec

[66ChevellePost]

I bought a used Solarex MSX53 50 watt panel off of E-bay. I paid $152.50(panel & shipping). If I got taken tell me, I am still learning. Anyway the specs are as listed

Pmax 50.8W
VOC 19.5V
Isc 3.68A
Vpmax 14.9V
Ipmax 3.41A
T 49 C
Pmax 36.4W
Ipmax 2.74A

So, I went out this morning to test it in the sun. I got a steady 16.95Volts and 3.4Amps. The outside temperature was 84 degree F according to my non-contact thermometer and the panel was about 115 degree F.

I know there is a relationship with the performance of the panel and the temperature. When I first attached my mulitmeter it showed 19+ volts and then began a decline until it reached 16.95volts. I am going to go out tomorrow morning to test in the cool morning sun.

How do you guys think the panel is performing with my initial test and the results of 16.95V at 3.4A?

Thaanks,
Kenny

[Mike90250]

I think you are pretty close to spec. STC power rating is about 20% high, as it's at 70F panel temp, not air temp. Any dark panel in the sun will be quite a bit hotter, as you measured. As panel temp p goes up, voltage goes down, like you measured.

[66ChevellePost]

Thanks Mike90250,

So you don't think I got taken too bad on the price I paid? Also is there a ratio of increase in temperature and the decrease in voltage(for example say for every 5 degree in temp increase I'll see a 2% or .5 volt drop in performance?)


Thanks,
Kenny

[Mike90250]

(for example say for every 5 degree in temp increase I'll see a 2% or .5 volt drop in performance?)

I paid about $400 -+ for a 64W unisolar, new, so, I think you did OK.

I think you are over estimating the voltage drop for heat though.