A Tale of Rechargeable Batteries

I have been using rechargeable batteries for a number of years, starting with nickel-cadmium and converting to nickel-metal hydride.  Although definitely better than disposable batteries, I have never been able to get even close to the number of recharge cycles advertised before the batteries no longer would hold a useful charge.. 

I recently purchased a Maha PowerEx C9000 WizardOne charger, which can handle any combination of four NiMH or NiCD, in AA and AAA sizes.  Each slot can be independently programmed to do a charge, refresh/analyze, break-in, discharge or cycle operation.  The refresh/analyze operation does a charge/discharge/charge cycle to determine the actual battery capacity, an indicator of battery health.  The break-in cycle 'forms' new batteries using an extended charging cycle and can also reactivate batteries that have not been used for a long period.

To speed up the refresh/analyze process, I tried topping up my batteries using my normal quick charger.  In a few cases, I found that the PowerEX charger would be able to charge the supposedly charged battery considerably further, sometimes up to an additional 50% of rated capacity.  This suggests that my quick charger was prematurely terminating the charge.  I have also seen cases where repeated refresh/analyze cycles significantly improved the measured battery capacity, from 1700 mAh to 2500 mAh in one case, and from 300 mAh (effectively dead) to 1400 mAh in another. 

At a minimum, the PowerEx charger will allow me to track battery capacity and ensure that all batteries in a set are matched (if one battery in a set has lower capacity, it becomes the 'weakest link').  Initial results suggest the charger will also significantly increase the lifespan of the batteries.  The one downside is the size: at 11 x 17 x 4 cm (4.5" x 6.5" x 1.5") it is a bit larger for travelling.