NiCads and NiMH batteries can and will develop mAh capacities based on their discharge/charge amounts. NiCads are the worst about this and NiMH aren't as bad...but they will develop a memory, too.

Typically I use a battery for a day's flying and then when back at the shop I hook it up to an ACE Super Smart Tester that drains the battery pack down to 1.05 volts per cell and also tells you how many mAh's were left in the pack. This way the batteries have been fully discharged and are ready to accept a FULL charge.

When I get a new battery pack I go through 3 slow charge/discharge cycles to "form" the battery pack. The ACE tester is used again so I know how many mAh's are on the battery pack. If three cycles don't bring it up to the pack's capacity rating...do it time or two more and then it should be up to par.

Older battery packs should be cycled to check for their condition at the beginning of the season and if you want to, more often. IMO, if a battery pack can't produce at least 90% of it's listed capacity...toss it!

Like a running engine, electrical power is your friend!