A method of charging a battery of a device using a battery of a computer powered by the battery, in which the procedure is implemented by a circuit independent of the computer's processors. The method includes supplying a power supply voltage, insufficient to charge a battery, to a computer port, as long as a device is detected as connected to the port, controlling the supply of a charging voltage to the port, while supplying charging voltage to the port, detecting an end of charging condition of a battery of the device, and controlling the cutting off of the charging voltage to the port if the end of charging condition is detected, where this condition is determined according to the intensity of a charging current and according to a quantity of electrical charge supplied to the port and/or of a charging period.