Nintendo Wii Fit 2800mAh Rechargeable Li-ion Battery Pack

NiCd must be fully drained before recharging (will shorten duration if you don't.) However, they take longer to wear out (and are cheaper than) NiMh.
NiMh can be recharged at any time, although the battery duration will get shorter through the life of the battery. Generally the best choice for rechargeble batteries in digital cameras, since the camera does not actually drain the battery completely.
Li-Ion are designed for devices that can be continually plugged in, charging when needed, and have the longest life (and one can purchase batteries of differing durations, if you want more). These are the most expensive and are the type normally included with portable electronics, like cellphone, laptop computers, iPods, etc. Needless to say, it's the best quality (and most expensive of the three.)

This is Li-ion battery pack,with large capacity rechargeable battery, can charge more than five hundred, it can also be charged through USB cable, moreover, it can be charging and using at the same time. I hope it can help you.

No, It just uses for Wii balance board power supply, It has a smart design, can be regularly serviced by fastening the balance board battery slot,  Nintendo Wii other product have their own battery pack.