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Newbe here building a cargo trailer and found some free panels on CL. Guy didn't know any specs on them all he said was they were 10 yrs old. That tag on the back left alot to wonder. I was trying to figure out the watts but tag had zero info I found useful. I hooked up a volt meter as it was in the sun and the meter was reading around 50v. I have a feeling this will not work for my 12 or 24v applications. Pic below of tag these panels are about 3 feet wide and 4.5 to 5 feet tall is a 48v panel a thing?
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The Ideal MPPT operating voltage of most panels is near 80% of the
open circuit voltage, or 40V here. You could short the output and
measure the current flowing under best sun to get an idea of capacity.
Again the MPPT current is in the area of 80% of the short circuit
current. So a 10A short circuit current under best sun would indicate
around 8A MPPT current, in that case power would be 8A X 40V =
320W.
An MPPT controller will match these voltages just fine to a 24V
battery system, actual numbers will vary from these first estimates.
If a panel has a bad section which gets internally bypassed, the
output numbers will be considerably reduced. good luck, Bruce Roe
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