A method is disclosed for connecting a plurality of battery strings to a direct-current (DC) bus. The method may include sorting the plurality of battery strings in an order based on respective output voltage values of the battery strings. The sorted plurality of battery strings may include, in the order, at least a first battery string and a second battery string. The method may also include connecting the first battery string to a pre-charge circuit. The method may further include pre-charging the DC bus using the first battery string and the pre-charge circuit. The method may further include connecting the first battery string to the DC bus. The method may further include connecting the second battery string to the DC bus.