Converting HP-25 to NiMH batteries, possible?

[BobVA]

(07-20-2022 07:48 PM)cubytus Wrote:  ...Well, since this HP-25 is not the "continuous memory" version, swapping the batteries would result in any program being erased.

... I used a battery contact spring to close the circuit in the battery box, but was surprised to see the calculator contacts weren't spring-based back then.

...So I understand that no-one attempted to convert the on-board charging circuit to NiMH?

1. All memory is erased in an HP-25 when the power switch is turned off, so taking out the batteries doesn't cause any (more) problems. :-)

2. Was there a battery pack in the calculator when you got it? It's a small plastic box that holds the two AA cells and has a spring-loaded interconnect on the end opposite the battery contacts in the calculator. The spring isn't mechanically connected to anything so, even if you get the pack, they are frequently missing the spring if the cells have been removed. The spring provides both the series connection between the cells and the spring tension to push the other end of the cells against the circuit board contacts.

3. Not that I know of.

4. Welcome to the forum!!!

Bob