Solar Panel Test.

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Hader

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Just wondering if this (photo) is how a Solar Panel is tested to determine its current Wattage. I'm testing 23 years old panels to see how much they are worth to sell or keep. The original rating was 90 Watts.
Screenshot_20220812-150214.png
 

wwhitney

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If the panel is pointed directly at the sun, and you use a volt meter across the leads, you'll get the open circuit voltage Voc. If you use an ammeter and short the leads, you'll get something close to the short circuit current, Isc (differing only by the resistance of the ammeter, not so clear on ammeters). But the power rating of the panel will be less than Voc * Isc, because the panel can't produce the full Isc while also producing Voc. If you look at a P-V graph of a PV panel, you'll see what I mean.

I don't really know any practical details about how to test old PV panels, but that's the basic theory.

Cheers, Wayne
 

Hader

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Thank you for the reply wwhitney. I saw some videos on how to do it, but still not sure if I'm using the correct settings (arrow in photo. 200m).
vm.jpg
 

wwhitney

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Your meter is correctly configured to read current up to 200 mA and is showing 49.3 mA. You can also try changing the dial to the 10A setting, I think it should then show 0.049 A.

If you know the currents you'll be measuring will always be 200 mA or less, you can leave the red lead in the middle location, and it will be a bit safer. But if you're wrong and the current exceeds 200 mA, then you may blow the internal fuse and have to open up the meter to replace it.

Cheers, Wayne
 
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sajesak

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If the panel is pointed directly at the sun, and you use a volt meter across the leads, you'll get the open circuit voltage Voc. If you use an ammeter and short the leads, you'll get something close to the short circuit current, Isc (differing only by the resistance of the ammeter, not so clear on ammeters). But the power rating of the panel will be less than Voc * Isc, because the panel can't produce the full Isc while also producing Voc. If you look at a P-V graph of a flexible solar panels, you'll see what I mean.

I don't really know any practical details about how to test old PV panels, but that's the basic theory.

Cheers, Wayne
I got new solar panels in last week. How (should) I test each one before installing them?
 

Fitter30

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If testing panels with a clamp on amp meter take a piece of wire loop it ten times amp meter clamps on to the loops, wire in series then divide by 10.
 

Linkraft

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Testing your 23-year-old solar panels to determine their current wattage is a great idea, especially if you're considering selling them or keeping them for personal use.
 
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