Chargers for NI-CD versus NI-MH batteries
There is a small, but non-zero, risk of overcharging NiMH batteries when using a NiCd charger.
The charge profiles of NiCd vs NiMH are very similar but not quite the same, since the 'peak' in the NiMH profile is less pronounced than for NiCd.
It's possible that a NiCd charger will miss it and carry on trying to charge a NiMH which is already full.