Abstract: A battery module including a connection terminal, a first battery, a second battery and a current limiting circuit is provided. The connection terminal serves as a power input terminal of the battery module during the charging of the battery module, and serves as a power output terminal of the battery module during the discharging of the battery module. The first battery is coupled to the connection terminal, and serves as a primary power source of a mobile device. The second battery serves as an auxiliary power source of the mobile device. The current limiting circuit is coupled between the second battery and the connection terminal, and restricts the magnitudes of the currents flowing into and out of the second battery according to a charging current threshold and a discharging current threshold.

Abstract: A mobile electronic system including a mobile electronic device and a charging accessory is provided. The mobile electronic device includes a first connector and a battery. The charging accessory includes a second connector. The first connector and the second connector are configured to couple the mobile electronic device and the charging accessory. When the charging accessory is coupled to an alternating-current voltage and the mobile electronic device, the charging accessory converts the alternating-current voltage into a direct-current voltage, detects an instantaneous voltage of the battery, determines the value of the direct-current voltage according to the instantaneous voltage, and outputs the direct-current voltage to charge the battery.

Abstract: A mobile electronic system including a mobile electronic device and a charging accessory is provided. The mobile electronic device includes a first connector and a battery. The charging accessory includes a second connector. The first connector and the second connector are configured to couple the mobile electronic device and the charging accessory. When the charging accessory is coupled to an alternating-current voltage and the mobile electronic device, the charging accessory converts the alternating-current voltage into a direct-current voltage, detects an instantaneous voltage of the battery, determines the value of the direct-current voltage according to the instantaneous voltage, and outputs the direct-current voltage to charge the battery.

Abstract: A battery module including a connection terminal, a first battery, a second battery and a current limiting circuit is provided. The connection terminal serves as a power input terminal of the battery module during the charging of the battery module, and serves as a power output terminal of the battery module during the discharging of the battery module. The first battery is coupled to the connection terminal, and serves as a primary power source of a mobile device. The second battery serves as an auxiliary power source of the mobile device. The current limiting circuit is coupled between the second battery and the connection terminal, and restricts the magnitudes of the currents flowing into and out of the second battery according to a charging current threshold and a discharging current threshold.