My First Classic

[Harald]

(08-21-2018 08:32 AM)jebem Wrote:  - Charging the battery inside the calculator using the original HP charger while at the same time you use the calculator.
It is a matter of time until you have the calculator fried when the battery makes a poor contact due to oxidation / dry electrolysis causing the internal circuits to receive unregulated power supply (this only applies to models where the charger plug uses two pins).

I am sure the many experts here will add more details and help on these subjects.

This is very good advice for most calculators, especailly woodstocks and spices. But the classics, with the exeption of the 65, do not have anything other than the charger connected to the battery. When the charger is unpluged, a bridge at the connector connects the battery to the calculator circuit. When the charger is plugged in, that bridge is opened.
So it is fine to charge the batteries in the calculator and even use it without a battery installed.

Cheers,
Harald