HP 41C series battery issues

[GreyUser]

The reversed battery trick works best with fullnuts and can most times allow recovery without the loss of memory. If that fails, a hard reset will always recover a locked up unit.

Locked up halfnuts are usually only recoverable with a hard reset and many times reversed batteries are the reason for the lockup. Of course YMMV.

Hard reset: Hold down the backspace key while turning on. See the MEMORY LOST message and it’s running. Without any previous programs