A charging method is provided for charging a plurality of batteries of a battery module. The charging method includes: obtaining a maximum voltage value and a minimum voltage value of a plurality of battery voltage values of the batteries according to a relative state of charge of the battery module during a charging process; obtaining a difference value between the maximum voltage value and the minimum voltage value; and adjusting a charging voltage value for charging the batteries and a taper voltage value for determining whether the batteries reach a charging saturation state according to the difference value.