Thinking about an HP-41CL

[Dieter]

(07-25-2016 01:28 PM)renif Wrote:  There are no ratings mentioned on the casing and I don't have a documentation either. But a quick measurement showed a stabilized charging voltage of approx. 5.4 V across fairly depleated cells.

If you measure the voltage between the battery contacts, this is the voltage of the cells (typically 1,2...1,45 V) which does not tell anything about the charging current.

(07-25-2016 01:28 PM)renif Wrote:  If i remenber correctly, there's a potentiometer inside the charger by which this voltage can be changed in a rather narrow range of 2 or 3 V.

If there is some kind of variable resistor inside it's more likely an adjustment for the charging current – or maybe the timer, if there is one.

Maybe you can measure the charging current? This could be done by removing one of the batteries, then reconnect it to the charger by the meter probes and an additional cable. Or you insert an isolating thin piece of plastic between a battery and one the charger contacts, with a piece of aluminium foil on either side so that you can connect the two leads of your multimeter. Should be something around 10...15 mA.

Dieter