Motomaster Eliminator Solar panels

[Ken Spenceley]

I have been given 4 of the above solar panels ( approx. 13" x 38" ea.) . I think they may be 15watt or possibly 30watt each. I am not sure which is the correct rating. How do I check the panels to see if they actually work and how can I determine their rating ? I am going to be using the panels for charging a battery bank with a capacity of 240 amp/hrs. Not sure whether to save these old panels or just buy a new solar panel .
thanks,
KAS

[Joe Blake]

My experience is that whilst solar panels tend to be self regulating, it's still possible to over charge a battery bank if it's not under any load, so I'd get hold of a regulator and an amp meter (with a shunt) to keep track of how much current is going in.

https://www.vicoffroad.com.au/sport-outdoor/solar-regulator/intelligent-home-20a-12v-24v-auto-lcd-display-solar-charge-controller.html

How to Wire An Ammeter and Shunt - YouTube

Hope that helps.

[Rob Beckers]

Ken, to see if a solar panel works there's two things to measure (with a multi-meter): The 'open' Voltage, between the positive and the negative when there's no load on the panel, it's not supplying current. That Voltage should reasonably correspond to the "Voc" number on the nameplate.

The other one is the short-circuit current. For a large panel you want to be careful doing this, but for a 30W little one you can just stick a multi-meter in the "Amp" setting between the positive and negative. Hold the panel up to the sun and check what current it is producing. There should be an "Isc" parameter on the nameplate on the back, that is the short-circuit current in full sun. Depending on how much light is hitting the panel you may see something close to that or not.

Four of those little panels aren't going to make much difference to a 240Ah battery bank; At best 4x 30W = 120W / 12V = 10A. If that battery is half empty, it'll take at least 15 hours of full sunlight (and panel output) to fill it up again, with no loads on the batteries...

-RoB-