Speed Optimized Multisine Stimuli for Electrochemical Impedance Spectroscopy with a Switched Mode Excitation

The knowledge of the state of a battery is a prerequisite for the battery management system to be able to increase the reliability, lifetime and safety of the entire energy storage system. Impedance spectroscopy is a well-known measurement technique for electrochemical systems. Once the method is implemented in the battery management system and performed online during operation it could provide a monitoring system for the battery pack. In order to perform the measurement online, the time necessary for it has to be as low as possible, which is best achieved with a multisine excitation signal. The distribution of the stimuli frequencies including their amplitudes and phases for such a broadband signal is presented. A reduction of the measurement time to the period of the lowest measurement frequency and an increase in measurement accuracy is achieved. The presented approach assumes that some kind of switched mode amplification is used to generate the stimuli current necessary to perform an impedance spectroscopy. Special attention has been given to narrowband distortions caused by the modulation process when selecting the stimuli frequencies.