Charging method, corresponding charging device and various corresponding uninterruptible power systems

A charging method, a corresponding charging device and various corresponding uninterruptible power systems are provided. The method comprises: controlling a charging circuit to charge a battery string and measuring a voltage of each battery; determining whether a start condition for performing a voltage balancing operation is met based on the voltage values of the batteries, and determining whether the voltage value of any battery is greater than or equal to a first threshold value; whenever the start condition is met, controlling a battery balancing circuit to start performing the voltage balancing operation until the voltage values of the batteries meet an end condition of the voltage balancing operation; and whenever the voltage value of any battery is greater than or equal to the first threshold value, reducing the output energy of the charging circuit until the voltage value of any battery is less than the first threshold value.