Battery system

Provided is a battery system including battery modules each having a plurality of batteries 20 and a battery module control unit 31 for controlling the plurality of batteries 20, and battery pack control units 230 for controlling a plurality of the battery module control units 31, wherein the plurality of the battery module control units 31 are connected in serial by wires between modules, wherein each battery module control unit 31 includes a first input/output terminal for inputting or outputting information to or from a battery module control unit 31 of one adjacent battery module 30 and a second input/output terminal for inputting or outputting information to or from a battery module control unit 31 of another adjacent battery module 30, and wherein an input impedance of the first input/output terminal is smaller than an input impedance of the second input/output terminal.