I have 2 20 watt Solar panel. I have it hooked up to solar controller and batteries to inverter. Am trying to figure out how much watts am getting. I found the voltage but how do I find the amp reading on a mutimeter?
While you can measure voltage on a like without a load, the measure of amperage is more closely related to the amount of power that is being drawn. The amperage is measured with the meter in series (not parallel like voltage) with the load. What it ends up measuring is the load that is being drawn from the solar panel and not the potential of the panel.
It is possible your meter does not have the capacity to safely measure more than 300 milliamps which is too small to measure current output from solar panels. Assuming no losses in the system or components, if your meter does not have the capacity to measure 0 Amps, you will need to get one that does. Analogs are better than digitial for this. Most often the 0 Amp circuit of the meter has a discrete positive plug location for the positive test lead. Most have a common ground connection with the rest of the meter functions. If you are measuring current at the battery in the charge mode- Negative lead of meter goes to positive terminal of battery and positive lead of meter goes to the cable that was connected to the positive terminal of the battery. Since the Wattage is a nominal measurement, if you measure between the panel and controller, take measurement on one leg of the panel, as you want to measure the current with the loaded active circuit. Meter is oriented the same way as the measurement at the battery would be made above only this time the meter is between the panel and controller. At peak solar conditions, expect current to be measured at 2.5 to3 Amps or more per panel. Under optimal conditions your panel will have higher output than their ratings indicate. Open circuit can be close to 20 volts. Never short circuit the output of the solar panels. It is volts multiplied by amps that gives you Watts.
