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I have a 29c since 1983, but cannot find a replacement battery pack.

Can I use other re-chargeable batteries instead if I opened the old chassis? What type and specs?

Please can any one help?




Standard AA pacs will run perfectly and far better than the original pacs !


You can replace the cells in the pack with AA Nicad or NiMH cells. The NiMH cells have a much larger capacity, are more enviromentally friendly, and don't have the "memory effect" problems of NiCad cells. They take more time to charge than the older Nicads (directly proportional to their greater capacity). The old Nicads were around 600 maH. NiMH cells can be found from 1200-1800 maH.

One thing to consider is that the HP29C is the most fragile calculator HP ever built in terms of what can happen if it is connected to the AC charger with a bad battery pack (or no battery pack) installed. If at all possible, charge the batteries in an external charger or a different Woodstock series machine.

I use standard AA's in mine. You can modify the original battery pack's plastic housing by cutting away the plastic piece which runs in between the batteries.

Modifying the original battery pack by cutting away the center bar so you can easily use standard AAs is a hell of a suggestion! I tried it immediately and powered up my 21, 25, 25C, 27, and 29C for the first time in years! Thanks!

I don't like doing the packs that way since they are no longer original looking (I have a few that were already done, and it is handy). I prefer to slice through the seam between the top and bottom halves of the pack and rebuild it with fresh rechargeables.