Measuring Voltage of a Charging Battery?

[Ether]

Patrick,

You might want to read this manual, it gives a lot of useful information about battery testing, and may answer your question:

http://www.crosstheroadelectronics.c...Manual_1_0.pdf

[DonRotolo]

The short answer is that the influence of the charger - it is supplying a voltage in excess of the battery voltage - complicates getting meaningful data from such a measurement.
Battery chargers generally use current, which eventually drops to near zero, as their monitored parameter to determine state of charge. More specifically, the change of the charging rate is monitored (the derivative (dx/dt) of current) and when it 'flattens' to a specific value the battery has reached a certain charge state.

[Jared Russell]

What we have done in the past is to have a momentary switch that cuts power to the chargers so that we can get an accurate reading (each battery is connected to a voltmeter and LCD display to give us voltage, but while the chargers are on you aren't just reading the battery).

Of course, this year between the new charger on sale from AndyMark and the Cross The Road Electronics Battery Beak, we will probably just use one or both of those.