Using non-rechargeable batteries on old HP calculators

[Dave Britten]

I "built" a new battery pack for my TI-58C a few months ago using a 3xAAA receptacle from Radio Shack soldered directly to the battery contacts on the board. Modern NiMH AAAs probably have comparable capacity to the NiCd AA-size cells that were used when the calculators were originally produced, and the smaller AAA receptacle was easy to fit inside the battery bay without any elaborate plastic fabrication. It's also easy to pop out the cells and stick them in a standard charger, which I prefer to do, as I don't know how the calculator would handle directly charging NiMH chemistry.

For cosmetics, I modified the original battery pack into a plain battery door to hide everything away. A Dremel works well for that step.