HP-41 Batteries

[Dieter]

(03-01-2015 10:27 PM)TASP Wrote:  Label on the transformer says HP92266A. Pretty funny, it looks like a 3rd party aftermarket gizmo, but what do I know?

Ah, yes, this seems to be the official "external" HP41 battery charger for four N-size NiCd batteries.

(03-01-2015 10:27 PM)TASP Wrote:  Specs are
117v AC 60 Hz 3W
5.8 VDC 15 mA

This seems to be a very simple charger without any charge control that applies a more or less constant charging current of 15 mA. This was fine for the NiCds of the day, but current NiMHs have much higher capacities and thus require very long charging times. Take the battery capacity in mAh and divide it by 12 (=15/1,25). The result is the charging time in hours for an empty (!) battery. In the Eighties, regular N-size NiCds offered about 120–150 mA which means a 10–12 hour charge. But a current N-size NiMH has about 500 mAh, so this would require 40+ hours... #-)

I would strongly recommend a better charger with decent automatic charge control. There are several suggestions in earlier posts in this thread.

Dieter