Just had a problem with 3 newish sets of AA NiMH batteries not holding power and showing up as faulty on my camera.This was despite regular conditioning.
After looking around on the net for info on battery charging I purchased the "Ansmann energy 4" charger , cost £29 plus pp,including 4 2400mAh AA batteries. click here It has microprocessor control of each cell, automatically detects faulty cells plus lots of other features.click here=
It seems to have done the trick as all my batteries are now functioning properly .
You should periodically run a re-chargeable battery completely flat, and then recharge.
If you do not do this, then they suffer from 'memory loss'. This reduces their capacity.
This is quite a technical subject, but I will not bore you about it unless someone asks. But basically the batteries have to be periodically recycled in order to maintain their efficiency, otherwise they can appear flat, when they are not!