The disclosure relates to a method for determining a Coulombic efficiency of battery modules of a rechargeable battery with a circuit arrangement connected to the battery modules. The circuit arrangement has multiple current paths, each of which has a series circuit of switch modules and at least one power semiconductor element which can be operated in a linear mode in order to regulate the current flowing through the respective current path, and one of the battery modules is connected to each of the switch modules. Each of the switch modules is configured as a switch module for selectively connecting the connected battery module into the respective current path or to alternatively remove the connected battery module from the respective current path. In each of the current paths at least one of the battery modules is selected with the switch module.