Originally Posted by A-Ko

If you use the NiMH every week;
After every race or use discharge them to .9v a cell or 5.4v (.9v X 6 cells = 5.4v) for the pack.

If you don't use them 3 weeks or longer;
Fully charge them for longer periods of time.
If you use them again charge and discharge at 20 amps to 5.4v two or three times and you should be good to go. With NiMH make sure they rest for 1/2 hour or more between charges or cycles. If you use a fan only cool them when you are discharging.