Battery pack and battery system including the same

A battery system comprising:

• a plurality of battery packs connected in parallel, each of the battery packs comprising:
• at least one battery cell;
• a first switch;
• a resistor circuit comprising a first resistor, and a second resistor connected to the first resistor in parallel and having a larger resistance value than that of the first resistor;
• a second switch connected to the first switch in parallel and configured to be turned on to be electrically connected to at least one of the first resistor and the second resistor;
• a communicator configured to obtain information corresponding to voltage values of other ones of the battery packs;
• and
• a controller configured to control charge or discharge of the battery cell in a plurality of charge and discharge modes according to a voltage value of a corresponding one of the battery packs and the voltage values of the other ones of the battery packs obtained by the communicator, the plurality of charge and discharge modes comprising a first charge and discharge mode in which the first switch is turned on, a second charge and discharge mode in which the second switch is turned on to be electrically connected to the first resistor, and a third charge and discharge mode in which the second switch is turned on to be electrically connected to the second resistor.