HP-25: charging of battery pack

[Geoff Quickfall]

Simple answer is no it is not a problem as long as the calculator is OFF.

The problem arises when the fallibility of the mind turns on the calculator while it is plugged in. The design risk that kills the ACT, ROM or RAM or a combination of one, two or three of those occurs when one of the three faults occurs:

1. Oooops, I forgot I took the battery pack out: infinite resistance.
2. Ooops, the battery pack is in but the batteries are chemically dead: infinite resistance.
3. Faulty battery contacts causing, you guessed it: infinite resistance.
   

All three place the 9 volts (?) of the wall wart through the ACT and further into the circuitry.

Therefore, to remove the possibility of destroying one or more ICs in the calculator, charge the batteries outside the calculator.

Geoff