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Determining the output of PV panels


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How does one go about determining by measurement what is the power output of PV panels if one does not have the specifications of panels?

Following on from that how is the amph rating of a deep cycle battery determined if you have no information on the system?

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With a solar panel you need a meter.

With the panel facing the sun, measure the voltage on the terminals. This should give you the open circuit valtage of the panel.

Now put the meter onto AMP's and measure again. This should give you a good indictaion of the max amps the panel can deliver.

Now you just multiply the 2 readings, 80% of that will be about the max watt the panel can deliver.

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Hi there,


regarding the capacity of a battery, perhaps check out



Charge the battery until it is full (13.8V ?), disconnect from charger, connect a constant load using 12V (maybe a set of lights?), should need a decent power value (250W?) otherwise the test will take forever. According to the website, you wait until the battery is down to 10.5V. I don't know whether is defined as empty or 20% full or whatever. Let's asumme it means empty.


Then full to empty at e.g. 250W takes e.g. 4h.... the capacity of the 12V battery would then by 4*250/12 = 83 Ah (any losses neglected)


I have never done it, so rather check with others.... Don't measure the current between the battery poles with a handhold meter, i blew my meters fuses.


Hope that helps a bit



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