HP41 Series Rechargeable Batteries?

[hth]

I used the original rechargeable pack back in early eighties. 5-10 years later I switched to rechargeable N cells in the ordinary battery holder and that is what I still use.

The advantage of the original pack was that you could keep it in the HP-41 all the time. I usually charged it every Sunday. These packs are no longer made and you need some work to rebuild one. It has lower capacity compared to N cells in the battery holder and need to be charged more frequently, but it is not bad with a weekly charge (with heavy calculator use).

Using N cells in the battery holder will last longer and is easier to replace. You need to take them out and it is a good idea to have additional batteries (or use alkaline batteries while charging). You also need to find a suitable charger.

I prefer the separate N cells as they last longer and there are no need to rebuild battery packs every five years. In some way it also depends on what batteries you can actually find. Both solutions work.