Charging and batteries for HP 34C

[Maximilian Hohmann]

Hello!

(10-20-2016 04:50 PM)Hsilop Wrote:  I am looking for an old HP 34C ...

Good luck with that, the 34C is one of the most difficult to find. And the prices asked are simply ridiculous. This whole "30 series" is not one of the best product lines from HP. It is almost impossible to find one of these without cracks in the (very brittle) plastic case or some degree of corrosion in and around the battery compartment.

(10-20-2016 04:50 PM)Hsilop Wrote:  I am guessing that rechargeable batteries in those days were quite different from those today, and would require careful maintenance in order to perform their best.

This calculators use the same 500mAh NiCd AA cells as most earlier ones. Nothing special there. Apart from the "memory effect" (https://en.wikipedia.org/wiki/Memory_effect) these batteries do not much differ from present day NiMH cells, apart from their much lower capacity. The only problem is that charging them with the original charger will take much longer because the charging current matches the lower capacity original cells.

Personally I replace the original NiCd cells (be careful when disposing them, Cadmium is very poisonous, best thing is to take them to a dedicated recycling station) with NiMH cells and charge those out of the calculator in a dedicated charger. Thereby the batteries will be charged they way they should be and there is no risk of damaging the calculator either.

Regards
Max