hp 35 batteries

[bill ledeen]

does anyone know if it is possible to get a replacement ni-cd battery pack for a hewlett packard model 35 scientific calculator? I already have an AC charger but my battery pack has failed and the calculator seems to require the battery for operation.

[Ellis Easley]

Actually, you can safely operate your 35 without the battery because the charger has separate outputs to charge the battery and to operate the calculator while the battery is charging. The gold plated metal fingers in the calculator's charger socket connect the battery to the calculator circuitry when the charger is unplugged. If you are having trouble using the calculator with the charger, maybe the charger is defective. The cord is subject to opening due to flexing, also I have read here several times that a transistor in the voltage regulator circuit inside the charger enclosure goes bad. Here's a thought - have you checked to make sure the "110/220" voltage switch on the charger is set correctly?

You can rebuild your battery pack, or get someone to rebuild it. The Museum has a page of information about this:

http://www.hpmuseum.org/repair.htm

Never throw away an HP battery pack because the parts can be used to rebuild the pack. There is a fellow who sells replacement battery packs of his own design to fit the 35 and other models, he offers them on Ebay. I don't see any of his auctions right now. However, I just noticed that his is the third name listed near the bottom of the Museum page I referenced above.

Also, you can sometimes find chargers for sale on Ebay.