I thought I would try this for the wii as it was inexpensive, really surprised at the quality small compact and looks great, plugs into the back of the wii with the supplied cable, the battery's are built into the new covers which are a excellent fit and have a small hole in them so you can sync your controls if need be, two supplied 2800mAh NiMH.
Remember to give them a good charge first time twelve hours at least, when you charge the lights on the docking station turn red and then blue once fully charged, for the price you can't go wrong, as two packs of decent alkaline battery's would nearly cost you the same.
Haven't had it long enough for a longevity test, but I will follow the usual guideline with rechargeable battery's, give them a good charge to start of with and run them flat, and another good charge and do that periodically.