Wii users may never have to take the batteries out of their wireless controllers again. Today Sanyo announced [JP] it has teamed up with Nintendo to develop a Wii battery and charger set that is based on the Eneloop concept. These low self-discharge NiMH batteries feature longer shelf life.

The Eneloop battery pack is placed on the back of the Wii controller. All you have to do after playing is to pop it into the charger stand and wait 220 minutes. The Wiimotes can then be used for up to 6.5 hours.

Up to 4 controllers can be charged by one AC adapter. Users don’t need to take off the silicone jacket from their Wiimotes as Eneloop cells are charged by magnetic induction (contactless recharging).

This is a great idea but it’s yet unclear whether Sanyo and Nintendo will offer the Eneloop set outside Japan as well (it hits Japan August 25th). Wii owners in this country will have to pay $23 each for the battery pack and the charger stand. The AC adapter will retail for another $9.