No Spec sticker: Is there a simple way to calculate a panel's wattage?

WYsolar

List,

This seems like a simple question, but I don't know how to answer it.

I was given two solar panels for free. The problem is there are no spec stickers on the back. I am assuming they are 12v, but I don't know. Likewise I don't know how many watt output each panel might be.

Question: How do I figure out the wattage and voltage of these panels??

They do work, so I would like to make use of them if I can...

Attachment not found.

BB.

Re: No Spec sticker: Is there a simple way to calculate a panel's wattage?

I would measure Voc (voltage open circuit) on a cool day, just after you take them out of a garage and put them in the sun (as they get hot, Voc will fall). Not that Voc is not really very dependent on the sun light--Even in weak sun, they should read full Voc.

And measure Isc (DC meter set to 10 amps full scale, leads across panel output). Note that Imp is not very temperature dependent (can be ignored). However, it is exactly related to the output of the sun. Measure Isc on a clear/bright day around noon with panel pointed square to sun.

Then I would just get a the Voc/Vmp/Isc/Imp from a another solar panel and scale the Voc/Isc measurements to Vmp/Imp.

If you have another good solar panel of known good quality--You can adjust your Isc measured for the unknown panel with the ratio of Isc-measured/Isc-rated for the known panel and adjust for solar irradiation.

Voc-unkn * Vmp-rated/Voc-rated = Vmp estimated for unknown panel

Isc-unkn * Imp-rated/Isc-rated = Imp estimated for unknown panel

Imp-estimated * Isc-measured known panel / Isc-rated known panel = Imp-unknown corrected for solar radiation to 1,000 Watts per square meter.

-Bill

WYsolar

Re: No Spec sticker: Is there a simple way to calculate a panel's wattage?

Thanks for the help, Bill.

I was hoping I could use my little digital volt/amp meter to get an idea regarding these panels. I will try measuring V and A across the leads and see what I come up with.