Which rechargeable battery you prefer for the HP-41?

[Dieter]

(08-22-2018 01:16 AM)mfleming Wrote:  I've used these and they worked well. Foolish me though, I recharged them in a unsuitable charger and continued to do so even after noticing how warm they were when removing them. One eventually leaked slightly but caused no damage.

Use good equipment!

Use suitable equipment!

The point is that N-cells require a much lower charging current than AA cells for which most chargers are designed. It's roughly 1/4 of the comparable AA current. That's why the BC-700 charger was recommended here: it defaults to 200 mA which for a 500 mAh N-cell means 0,4 C. This is a rate that is low enough for most current NiMH batteries and high enough to provide the required voltage drop for end-of-charge detection in a smart charger.

On the other hand, if you put such a 500 mAh cell (with an adapter) into an AA-charger that is set to 1000 mA you'll fry the battery with 2 C. This is a rate that exceeds the limits for most N-cells. You described what can and will happen then.

Dieter