Solar Panels - Determine Rating, Power

First, can you show us a picture? Maybe we can identify the manufacturer.

Second, put the panel output across a known resistance and measure amperage. Do the math for approximate wattage.

Third, 40 volts seems a little unusual to me. Make sure you're testing under best sunlight conditions. Let us know.

Dear RDGNR,

Thanks alot for your response. Fortunately, we found the panel specification on another batch. The panel is a 24volt,Umpp 34.8v, Impp 3.14, Uoc 43.2v, Isc 3.38A, MAX SYSTEM VOLT 750V.

Obviously i have to connect these panels in parellel since the inverter is 24v 2200W and the battery bank will have an output of 24v.

What will be the rating of charge controller that will charge these four 12v 200Ah batteries.

4 panels X 3.38 amps= 13.5 amps (324 watts)

Oversize your charge controller a bit and get one with MPPT (maximum power point tracking) and it will increase your annual PV output by 20% or so... more when it's colder less when it's warmer.

Of course your 40 vdc reading was with the panels open circuit.

Hi, thanks for your assistance thus far. My little project is almost over. One more thing, can these four solar panels rated at 110 Watts, each at 24volts be able to charge four 200Ah batteries. I've already connected the panels in parallel giving me an output of 24volts. The four batteries have been connected in series/paralle giving an output of 24volts. By the way, the 2200watts inverter to which the batteries are connected will be used to power a 1hp pump to pump water from a deep well onto surface tanks.

Thanks alot for your assistance.

Depending on your inverters surge capacity you should not have any problem running your pump (746 watts) but you'll need 2 hours of insolation for every hour you run the pump. I think you'll need another charging source or more panels to keep your batteries up. And you'll need a Genset or grid connection to equalize your batteries. If you are only running the pump in short spurts and infrequently you may be able to eek by with what you have, depending on other load demands.

Never use INVERTERS with solar panels. They will cost you a lot in lost energy. A DC motor will pump the same amount of liquid with less than 50% of the energy. A new DC pump will cost LESS than an Inverter. If you get a really good DC solar pump then you can replace your 750 watt AC motor with a 150 watt DC motor and pump the same amount of water. Also you can save the cost of buying the Inverter. Note: If you use Thin Film PV panels you will get an average of 30% more Annual yield than Mono Crystalline panels, so pump even more water. Use a pump with a Solar Controller to maximise output.

First, take a minute and browse this, then jump over here for your math. Follow the links to tech resources and how to calculate battery run time. Amperage formulas are there; select your 24V charge controller accordingly.