It's probably longer than you're thinking...

Nintendo's controversial 3DS slider pad expansion has made its debut in Japan with advanced Monster Hunter Tri G copies, and eager gamers have already been forensically examining the ins and outs of the device.

One consumer has confirmed (via Andriasang) that the manual of the Circle Pad Pro states that the device runs for 480 hours on one AAA battery. Which is probably a good thing, seeing as the battery compartment requires a screwdriver to access.

The device works by clipping around the 3DS and feeding data to the system via the small infra-red port next to the stylus holster.

The Circle Pad Pro lands in Europe alongside Resident Evil: Revelations on January 27th.