I have had a cordless drill (AEG 9.6v) for about 15 years
Over this time have replaced the nicads in the battery packs.
Nicads these days are Na-Poo and I bought NiMh cells instead, but still found life in the old cells.
How close is the match of the standard voltage of single cells between NiCad and NiMh?
Are they both rated as 1.2volts?
The fast charger supplied, seems sophisticated enough to respond to the voltage and signal when fully charged. The battery packs have a heat sensor and will presumably cut off if the pack heats up too much.
I realise capacity and Charge/Discharge rates may differ.