A battery system includes: a plurality of battery banks connected in parallel with each other; and a distribution controller coupled to the battery banks and configured to: receive a command comprising a target charging/discharging amount; determine a priority order between the battery banks based on a state of charge (SOC) and a state of health (SOH) of each of the battery banks; select at least some of the battery banks to be charged or discharged according to the target charging/discharging amount based on the priority order; and perform a charging or discharging on the at least some of the battery banks according to the target charging/discharging amount so that others of the battery banks are paused.