HP 21 Rechargeable Battery Needed

[Sarah Mulder]

I have been looking for a set of two rechargeable batteries for my HP21 Calculator. I have discovered that it needs two 4 volt rechargeable batteries but I am unable to find where to purchase these. If anyone knows where I can find two rechargeable batteries for my HP21 Calculator, it would be greatly appreciated.

Thanks,

Sarah (for Vic)

[Thibaut.be]

Hello,

So you have the original battery pack ?

If so, it it quite easy with a cutter to open the old one and replace the original dead batteries with 2 AA rechargeable batteries.

Fiding a woodstock battery pac is not only difficult, but if successful very expensive.

Don't forget that woodstock calcs might fry if connected on the power supply without batteries !

[Jose Goncalves]

Two 4 V batteries ? I don´t think this is the correct value ! pls check that.

[Thibaut.be]

Of course you're right, AA rechargeable batteries supply 1,25 V, and that's just what a woodstock need, ie 2,5 V.

[Tony Duell]

Why do you believe it needs 2 * 4V batteries? Every Woodstock (HP2x) series machine I've repaired runs off a 2.5V (or so) battery pack consisting of 2 AA-size NiCd sells in series.
If you have the oriignal battery pack, you can carefully cut it open, extract the original cells and put new ones in. If you don't have the original pack, you'need to find one, etiher working, or to be rebuilt. As a general comment, _never_ throw out old HP calculator battery packs -- the plastic housing, and some of the metal contact strips are needed to rebuild the pack.