A battery system includes: a first battery module including a plurality of first battery cells; a second battery module including a plurality of second battery cells; a battery disconnection unit connected between the first battery module and the second battery module, the battery disconnection unit including: a first main switch connected in series between the plurality of first battery cells and the plurality of second battery cells; and a precharge switch and a precharge resistor connected in series with each other and connected in parallel with the first main switch.