Hi,
Ni-Mi batteries like to be charged SLOWLY, around 10% to 20% of their RATED mAH capacity. Do Not crank up the current and get the battery pack hot, it will take the charge, but the batteries will be damaged and not last nearly as long as packs that were not over-heated while charging. Your charge rate for Ni-Mi should be 10%-15% of the rated battery capacity. A 1000 mAh battery pack can be charged at at 100-150mAh for 10 hours. A 2000 mAh pack can be charged for 10 hours if your charger puts out approximately 200 mAh. Again, DON't Let your Ni-Mi pack get HOT.

Ni-Cd batteries can take lots of abuse, over-charge, getting hot, and over drained. But, they do need to be cycled and checked for capacity. Any Used Ni-Cd or Ni-Mi packs should be thrown away if they will not check out to within 80%-85% of it's original rated capacity.

Battery manufacturers rate the capacity of their batteries with a normal discharge of 50 mAh.

A normal 4 channel .40 size airplane with 4 standard Servos will pull approximately 250 mAh
per hour of constant use. For many Years, Radio manufacturers use standard 600 mAh batteries in the Transmitter and Flight pack. This gave a TOTAL of about 2 Hours of Flying Time before the batteries required a re-charge. 600 mAh / 250 mAh = 2.4 Hours of battery life.

Larger capacity batteries may give you a warm and fuzzy feeling, but don't forget to re-charge every time and re-cycle once each month to verify those batteries.

Batteries are cheaper than airplanes.

Ken AMA 1528