Method for initializing and operating a battery management system, comprising the steps of: starting the battery management system; reading battery variables which are stored in a nonvolatile memory of the battery and comprise the last state of charge (SOC old) of the battery; measuring the open-circuit voltage of the battery; determining an instantaneous state of charge value (SOC inst) on the basis of the measured open-circuit voltage; determining an estimated value of the state of charge (SOC est) of the battery as a function of both the stored last state of charge (SOC old) of the battery and the instantaneous state of charge value (SOC inst); initializing the state of charge in the battery management system using the determined estimated value of the state of charge (SOC est); and operating the battery management system with the initialized values, characterized in that a plausibility check of the state detection by the battery management system is also carried out, comprising the steps of: comparing the instantaneous state of charge (SOC inst) and the state of charge stored last (SOC old); switching off the battery if the difference between the instantaneous state of charge (SOC inst) and the state of charge stored last (SOC old) is above a predetermined threshold value; or initializing the battery management system with the determined estimated value of the state of charge (SOC est) if the difference between the instantaneous state of charge (SOC inst) and the state of charge stored last (SOC old) is below the predetermined threshold value, wherein, before the battery management system is switched off or before initialization, a further plausibility check of the values is also carried out by comparing the calculated state of charge (SOC inst) dependent on the open-circuit voltage with a current integral. starting the battery management system; reading battery variables which are stored in a nonvolatile memory of the battery and comprise the last state of charge (SOC old) of the battery; measuring the open-circuit voltage of the battery; determining an instantaneous state of charge value (SOC inst) on the basis of the measured open-circuit voltage; determining an estimated value of the state of charge (SOC est) of the battery as a function of both the stored last state of charge (SOC old) of the battery and the instantaneous state of charge value (SOC inst); initializing the state of charge in the battery management system using the determined estimated value of the state of charge (SOC est); and operating the battery management system with the initialized values, comparing the instantaneous state of charge (SOC inst) and the state of charge stored last (SOC old); switching off the battery if the difference between the instantaneous state of charge (SOC inst) and the state of charge stored last (SOC old) is above a predetermined threshold value; or initializing the battery management system with the determined estimated value of the state of charge (SOC est) if the difference between the instantaneous state of charge (SOC inst) and the state of charge stored last (SOC old) is below the predetermined threshold value, wherein, before the battery management system is switched off or before initialization, a further plausibility check of the values is also carried out by comparing the calculated state of charge (SOC inst) dependent on the open-circuit voltage with a current integral.