Impedance-based battery monitoring

This thesis deals with the application of impedance measurements for battery monitoring systems. A robust and efficient measurement procedure has been developed that facilitates impedance measurements in an automotive environment. The measurement is purely passive and uses current fluctuations in the vehicle power grid as a signal source. By that means, the momentary state of the storage system can be measured during normal operation. This method is complemented by selfadapting characteristic maps, allowing the description of the battery characteristic in the complete operating range even in the presence of ageing effects. The application of the passive impedance measurement technique for battery monitoring is discussed in detail for two examples: the monitoring of ageing effects of double layer capacitors and the cranking capability prognosis of lead-acid batteries. Based on the modelling of the storage systems by impedance models, the key parameters are identified and their dependency on ageing processes is analysed. The monitoring and prognosis procedures derived from this analysis have been implemented both in a simulation environment and on a microcontroller-based measurement system and were tested experimentally.