Abstract: A battery charger for a personal electronic device comprising: a housing, a battery energy storage unit, a battery charging circuit, an electric power converting circuit, at least one power input portion and at least one power output portion. The at least one power input portion includes a plug or socket for connecting to a socket of A.C. source, and a D.C. socket that can be connected to a computer through a USB interface for charging the battery charger. The power output portion has an interface able to connect to a mobile phone or electronic device for charging the latter. The power output portion can also design as a socket, and disposited at the same position on the housing with the D.C. socket of power input portion. The battery charger can be connected to a personal miniature electronic device, such as a mobile phone, a digital camera or an MP3 player, for charging the device by using the battery energy storage unit as an energy source.