This simple rechargeable battery pack made specially for the Wii Fit balance board will make sure you always have enough power for your workout. Simply plug one end of the supplied USB cable into your Wii and the other end into the battery pack and leave it to charge. One fully charged the powerful 3800mAh battery pack will then give your hours and hours of trouble free workout fun. Don't forget you will also save a huge amount of money from not having to buy disposable batteries, a must have item.