The MH-C204W battery charger has a 5th generation PowerEx microprocessor that features a unique four stage charging process:

-Ramp-up
-Rapid Charging
-Top-off charging
-Maintenance Charging

The Ramp-up jolts the rechargeable batteries if needed to revive old batteries.  This jolting feature is a series of carefully timed high current pulses that can activate both new and inactive batteries.

The MH-C204W is designed with an intermediate, medium current, top-off charge so that the rechargeable battery will retain most of its charge.

The Maintenance Charging feature is an extremely low current pulse charging that gives the rechargeable batteries a brief pulse charge periodically to ensure the batteries are charged but not overcharged. This feature actually allows you to leave your batteries in the MH-C204W charger while plugged in - without any fear of over-charging your nimh rechargeable batteries.