Rechargable batts for a HP25C, but how?


Hello fellow enthusiasts.

I am aquiring an usable (he said) HP25C with a broken rechargable battery. How is that fixed?
Matti Sweden


Replacing the cells is quite easy. Just make a cut in the end of the plastic strip that runs between the cells and remove the old cells. You can replace the cells with any NiCad, Alkaline, Li-ion, NiMH cell you want (AA size). There are occasional size variations that can make some cells work better than others, but all can be made to work. Make sure you get the polarity right- easy to check by noting polarity of cells removed, or info is available on this site. Of course alkaline batteries can not be recharged. It is not a good idea to recharge your batteries in these calculators due to potential damage to circuitry. Of course the original charger circuit was not designed for Li-ion or NiMH, but this is not an issue if you do not recharge them in the calc, and I am not sure if it is an issue in any case. Again - please do not recharge in the unit as poor contact with the battery can destroy the calc circuits....


Very easily.
- with the blade of a cutter, desolidarize the battery holder
- remove the old batteries and clean up the compartment
- buy 2 AA rechargeable batteries, the most common type you can find
- put them into the holder, respecting the polarity + and - are written on the compartment
- glue the part you deloidarized.

Put it into your calc and charge it.

Enjoy your calculator for the next 20 years, then repeat the operation


If you'd like to retain the stock look, instead of cutting the thin plastic strip in the battery pack, it is possible to *carefully* pry the two halves apart with a strong, sharp knife. I've done this with several, and installed NiCad AA cells (see the "Replacement Nicads for HP Battery Packs" article elsewhere on the site). Make sure you have the polarity correct and the spring in place, and stick the halves back together with a few small drops of glue.


OK folks,

Very much thank You all!!

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