The invention relates to a method for operating a battery system (2), which comprises a plurality of battery cells (8) and a battery management system for monitoring and controlling the battery cells (8), wherein the battery management system has a main control device (4) and a plurality of cell control units (10), wherein each cell control unit (10) is associated with one battery cell (8) and is designed to capture measurement data of the associated battery cell (8) and to connect and disconnect the associated battery cell (8) to and from an electronic circuit of the battery cells (8). According to the invention, each cell control unit (10) detects whether the battery system (2) is currently being charged or discharged and, in dependence thereon, connects or disconnects the associated battery cell (8) to or from the electronic circuit of the battery cells (8). The invention further relates to such a battery system (2) and to a motor vehicle.