The concept is simple, and follows the logic that allows a USB port to operate small electrical appliances. Here it is used to store energy to recharge batteries.
A battery charger, this is not new, but thanks to a USB port on your laptop, then it becomes a much more interesting. Rechargeable batteries can be of size AA and AAA Ni-Cd and Ni-MH. The device enables support for up to two batteries simultaneously. As with any device of this type, an LED lets you know the condition of battery.
Data Sheet