Electronics > Power/Renewable Energy/EV's

New Solar Panel Test -

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Dunk_c:
Hi

I just received a "60w" panel and tested at ambient temperature before the glass got hot, in full sun, no clouds, 11:35 am, Qld.

The product label states 21.6v VOC and 3.77A ISC, Vmp 17.7, Imp 3.39, 60w.

When I tested the panel the VOC is 23.2V and the ISC is only 2.1A.

When the panel is attached to a 10ohm 200w power resistor the panel only delivers 1.8A at 18v, or 32 watts, when cool at midday. I should have measured the solar irradiance but forgot.

These panels are made from 125x125 Sunpower Maxeon cells cut into 1/3 (125x41); 36 joined together in a 36 cell string.

The spec for the Sunpower Maxeon 125x125 cell is 6.28A Isc. Dividing this by 3 = 2.1A. This is the max SC current produced by the new panel.

According to some specs I found online, the full 125x125 cells theoretically produce 0.687v Voc. Multiply that by 36 cell in the panel and you get 24.7V, similar to what I measured 23.2V, plus some drop across the diode.

The label on the panel and the rated output cannot be correct. Seems like half the amps are missing!

Comments wanted before I question the seller.

Thanks

HackedFridgeMagnet:
As long as its not cloudy you don't need to worry about irradiance. It will be close enough.

Vmp 17.7 / Imp 3.39 = 5.22 ohms. This load will give closest to maximum power.

Your ISC should match the specced ISC.  Maybe half the panel isn't connected?

Maybe you had a shadow on the panel or maybe your panel wasn't perpendicular to the sun or maybe your panel just not as good as it says.


I can't think of another reason.

Ian.M:
Do an A/B test with a known good panel side by side with the suspect one, and video your test procedure, so (assuming the good panel meets specs,) the seller cant claim "It must have been hazy when you tested it".  :-BROKE

HackedFridgeMagnet:

--- Quote ---These panels are made from 125x125 Sunpower Maxeon cells cut into 1/3 (125x41); 36 joined together in a 36 cell string.

The spec for the Sunpower Maxeon 125x125 cell is 6.28A Isc. Dividing this by 3 = 2.1A. This is the max SC current produced by the new panel.
--- End quote ---

Yes this sounds significant. I missed it before. Your calculation seems right and their spec is wrong.

Dunk_c:
Definitely no clouds, clear blue skies, but will check again in case it was a little hazy.  Recorded max values as the panel was moved about.

Don't have a 5ohm resistor.

Clearly the Isc is only a little more that half the quoted value.

The panel voltage would suggest that alll 36 are connected.

Don't have a an identical second panel for confirming.

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