Battery charging circuit

The invention provides a battery charging circuit comprising a power supply input unit, a plurality of charging units and a control module. Each charging unit comprises a charging port for connecting a battery, a coil and a switch combination connected between the charging port and the coil, the coils of the plurality of charging units are rolled on a same iron core, and the switch combination has an off-state, a discharging state and an auxiliary charging state. The control module is provided with a plurality of connection pins and a plurality of control pins, wherein the connection pins arerespectively connected with a charging port and used for detecting voltages at two ends of the charging port, and the control pins are connected with the switch combination to control the working state of each switch combination. The control module detects and compares the voltages of charging ports of different charging units, and controls each switch combination to be in a corresponding workingstate according to the com