A battery management system which can output a battery state enabling optimum charge and discharge control to be performed even when a temperature variation occurs among individual single cells. The phases of the winding arrangement are connected to a vehicle network with the aid of power converters and the winding arrangements are interconnected in a first method of connection for motor operation and interconnected in a second method of connection for generator operation. The synchronization object is transmitted by a local user computer at any time to a routing agent, which in turn transmits the synchronization object at any time to remote user computers within the sharing community. In an embodiment, oxide is removed from the bumps by a plasma treatment.