hp67 82004A reserve power pack

[Katie Wasserman]

The charging rate/time on nicad cells is not critical, as they can tolerate overcharging pretty well. Newer nicads can charge at much higher rates (faster times) than old ones without damage. The best way to tell if a nicad battery pack is fully charged is to remove it from the charger and measure it's voltage. Fully charged, it should measure 1.45 volts x number-of-cells.

NiMH cells are not as tolerant of overcharging and hence the HP calculator charging systems aren't the best for them but they still work and you should measure about 1.6 volts fully charged, but you really should never fully charge them to maximize their lifespan.