A simple guide of charging NiMH batteries
The charging efficiency of nickel base is close to 100%, up to 70%. The pack stays cool, but it starts to heat up, its efficiency decreases and it is fully charged.
NiMH batteries must be cooled during charging. If it is warm, the charge current is too high.
Consumer chargers may not always terminate charging correctly. Remove the battery when it is hot to the touch. Stop using the charger for the "cooking" battery.
Charge at room temperature. Do not charge in high temperature or freezing temperature.
NiMH batteries are best fast charged; continuous slow charging leads to "memory".
NiMH and Lithium batteries require different charging algorithms. NiCd charger will overcharge NiMH.
Leave the NiMH battery in the charger for more than a few days. If possible, remove the packaging and charge it briefly before use.