On Feb 16, 10:38*am, Winston wrote:
Jim Wilkins wrote:
On Feb 16, 3:18 am, "PrecisionmachinisT"
*wrote:
*wrote in message
...

Right, but this isn't a 'pure' DC circuit.

By mentioning 'impedance' instead of just ESR, I hoped to remind us
that the current waveform into the battery is dependent on
it's Equivalent Series Resistance *as well as* how it 'looks'
to the pulses of D.C. from the rectifier, in the frequency domain.

See for example, Table 1 of:http://www.telepower.com.au/INT95b.PDF

Interesting.

The test I've seen and done for battery impedance is to measure the
voltage at a steady low-level current, then pulse on a higher load and
capture the voltage and current waveforms on a digital storage scope.
The impedance is the slope of the line between the low and high
current V and I, at a place on the waveform chosen by the battery
engineer. The higher frequency effects which are relevant to PWM motor
drivers are easily removed with capacitors. The low frequency
impedance (mostly resistance) is a good measure of the condition of
the battery.

jsw