My HP67 Has Melted!!!

[Maximilian Hohmann]

Hello!

(03-20-2020 12:28 PM)BillBee Wrote:  I've seen Lithium Ion battery packs melt ...

This is due to an effect called "thermal runaway" (https://en.wikipedia.org/wiki/Thermal_runaway#Batteries). Low power density NiCd or NiMh cells as in the HP-67 should not be affected. I am 99% sure that this calculator melt down is not primarily caused by the battery but by the circuitry around it.

Anyway, this example shows that it is always wise not to charge historical electric devices unsupervised.

Regards
Max