BATTERY SYSTEM AND CONTROL METHOD

A battery system includes: a charging apparatus; a plurality of battery modules to connectable in parallel with the charging apparatus; and a controller, in which each of the plurality of battery modules has a battery, and the controller obtains, when a charging command is received, a voltage value of the battery of each of the plurality of battery modules, identifies a first battery having a lowest voltage value and a second battery having a second lowest voltage value, starts charging of the first battery, and after starting the charging of the first battery, starts charging of the second battery when a difference value between a voltage value of a first battery module and the voltage value of the second battery becomes equal to or less than a first threshold value.