Lithium (coin cell) backup battery

[Jonathan Busby]

I know of no HP calculator* ( unless you consider the HP 100LX/200LX calculators ) that uses a backup battery. As has already been mentioned a capacitor is used to supply voltage to the SRAM when the batteries are being changed.

On another note, if you use lithium based non-rechargeable batteries ( eg. Energizer Ultimate Lithium AAAs ) be aware that when the batteries are almost fully discharged and you get a low battery warning you need to replace the batteries ASAP because unlike regular alkaline batteries lithium-based batteries tend to drop to almost 0 volts when a load is applied when they're almost dead. Take it from me : I've been bitten by this behavior several times and have consequently lost my calc's memory.

Regards,

Jonathan

* At least Saturn based...