solar panels

[gonad]

hi all anybody out there can tell me how to know whether a panel is any good? using a digi voltmetre perhaps total tech dunce me the plates are slightly brown what does that mean? second hand bargain or waste of money?either 40 or 50 watts for 100euros ta 4 any advice

 

[VicS]

(i)Put it in the sun and connect a voltmeter to it. You will get a reading well over 12 volts if it is any good.
(ii)connect a load to it say a car head lamp bulb if you think it is 40 or 50 watts. It should light in bright sun but maybe not full brilliance. Check the volts again It wont be over 12 this time. Try a smaller bulb if the head lamp bulb does not light

A 40watt panel is going to be something like 1/3 sq metre in area but check catalogues or websites for actual dimensions.

You will need a regulator if you are going to use it for battery charging.

 

[sarabande]

Gonad

Can you post on only one forum at a time pls ? It makes life confusing if you multi-post, and useful answers may otherwise get lost.

/forums/images/graemlins/grin.gif

 

[William_H]

The best test is to connect an amp meter directly across the output. In bright sunlight facing the sun.This might seem like you are shorting the output and will destroy the panel. not so. You can use an old car headlight bulb if it worries you.
You should of course also measure near 20 volts no load in the sun.
The power rating of the panel will be the 20 volts multiplied by the max current in watts. If you get something like half of what you expect then it is probably OK. olewill