The Dual DOCK is the most convenient way to stay in the game. Charge 2 Wii Remotes at the same time using the 2 included rechargeable battery packs. Simply replace the batteries and the cover of your Wii Remote with the included rechargeable battery pack, and place in the dock to begin charging. The LED indicator will let you know when the batteries are fully charged. The rechargeable battery packs can be charged with or without it the Wii Remote. Now there is no need to search for another spare battery for your Wii Remote.