Battery module

A battery module, comprising:

• a connection terminal, wherein the connection terminal serves as a power input terminal of the battery module during charging of the battery module, and serves as a power output terminal of the battery module during discharging of the battery module;
• a first battery, coupled to the connection terminal, and serving as a primary power source of a mobile device;
• a second battery, serving as an auxiliary power source of the mobile device, wherein an energy density of the first battery is greater than an energy density of the second battery;
• a current limiting circuit, coupled between the second battery and the connection terminal, and designed according to a format of the second battery for restricting magnitudes of currents flowing into and out of the second battery according to a charging current threshold and a discharging current threshold;
• and
• a current limiting controller, coupled to the first battery, the second battery and the current limiting circuit, and controlling whether the current limiting circuit restricts the magnitudes of the currents flowing into and out of the second battery according to a voltage of the first battery, a voltage of the second battery, a maximum charging current that the second battery is capable of receiving and a maximum discharging current that the second battery is capable of providing, wherein
• the current limiting circuit comprises restricting the magnitude of the current flowing into the second battery not to exceed the charging current threshold when the first battery and the second battery are simultaneously charged through the connection terminal;
• and
• the current limiting circuit comprises restricting the magnitude of the current flowing out of the second battery not to exceed the discharging current threshold when the first battery and the second battery are simultaneously discharged through the connection terminal.