Some large PVs for rooftops were at a street market for €35 each. I’m not deeply knowledgable about them.. I just know that there are two varieties of solar panels and that the kind that are used from small appliances (e.g. calculators, speakers, lawn lights, etc) are junk. And that junk variety is sometimes used in large rooftop panels. What I was looking at resembled the kind I see on a bluetooth speaker with a slight blue tint so I was skeptical. The info on the backside of the panel indicated “1000 V”. The other thing is, all solar panels degrade over time and reach end of life after like 15 years (though this is improving). They may have been a good deal but I passed on them because I didn’t want to buy them on a blind risk.
How would I know how much life a used PV has left? Would a volt meter give that info, assuming it’s sunny when I encounter them again?
Just informing you: You can see the power output of PV panels by looking at the Watt number. It says something like 400 Wp (Watt peak - i.e. Watt under direct sunlight). Voltage is more or less irrelevant.