Using non-rechargeable batteries on old HP calculators

[Dieter]

(12-03-2014 11:16 PM)Katie Wasserman Wrote:  I use Energizer lithium cells in and they're up to 1.7 volts per call, so quite a lot higher than nicad's. I've never had a problem doing this with any HP calculator: classics, woodstocks, spicse, stings, etc.

Thank you very much, and sorry for my late reply. Finally I would like to add two remarks:

According to the graphs in the Energizer L91 datasheet the voltage almost instantly drops to 1.5 Volts or below if the load is 10 mA or higher. All LED calculators should exceed this load, so I wonder if the actual voltage applied to such a calculator really is not much higher than these 1.5 Volts, even if a fresh set of batteries is used.

Finally I would like to ask if someone has looked at the schematics of a Classic, Woodstock or Sting series calculator, especially at the voltage supply, and may dare an educated guess from there regarding the maximum "safe" battery voltage. I understand that even Lithium cells obviously do no harm, but maybe this observation can be confirmed by a closer look at the schematics. ;-)

Dieter