Fast charging vs slow charging

Charging Ni-MH batteries at the lowest possible current is not always the most beneficial for their lifespan.

In the case of modern automatic chargers, the assessment of the moment of full battery charge largely depends on the charging current value.
The best charging result is obtained with a current value of no less than 1/5 of the battery capacity (e.g., 400 mA for an Eneloop AA battery min. 1900 mAh).
Remember that faster charging using higher charging currents is not harmful to batteries, as long as it does not lead to a sudden increase in cell temperature above 50°C, which should not occur even with a charging current equal to 1/2 of the battery capacity.