USB Charger for Woodstock

[Bill Duncan]

(04-01-2023 06:14 AM)Docj Wrote:  Hallo,

after reading all of the answers, now i am unsettled.

I have two HP 29C and i just bought new NiCd battery packs (a little bit difficult in the EU) and i have two original chargers but now it seems to me that it is a risk to kill my calculators when i use them?

With kind regards
Juergen

Yes. Do NOT use the calculators with the charger plugged in. There are numerous threads on this. The design uses the battery to regulate the voltage. Even a momentary loss of contact with the battery will fry the electronics.

There are 3d printed battery pack containers available if you need a spare. I've simply disassembled the original by taking out the middle post. You can then replace the nicads. If you replace them with NiMH, just make sure that you charge them outside the calculator. It will also work nicely with alkaline cells.