Electronics: How to measure power output by a battery charger.

A typical battery charger designed for lead-acid batteries uses either half-wave or full-wave rectification (but NO filtering). Because of this, the applied waveform is not sinusoidal. In order to calculate the Voltage and Current, the values must be converted to RMS. However, connecting the battery does a very good job of doing this. Values measured with the battery connected, will reflect the actual voltage on a DC meter. The formula is E(rms) * I(rms).