Method for Monitoring a Battery System

A method for monitoring a battery system having a battery module that has a plurality of battery cells. A battery management system is not active in a sleep mode of the battery system. The method includes monitoring a measured value in the sleep mode by a sensor arrangement and comparing the measured value with default values by the sensor arrangement. A wake-up signal is triggered when the measured value deviates from the default values which ends the sleep mode, activates the battery management system, and starts an emergency mode. The method also includes alternatively triggering the wake-up signal when a predefined wake-up time is passed and determining and predefining a new wake-up time and new default values before the battery management system switches into the sleep mode again.