The research group at HAW Hamburg investigates the monitoring of battery cells utilizing the electrochemical impedance spectroscopy (EIS), which is an important method for analyzing battery condition and ageing. Although EIS is widely used in the lab, it is not yet implemented as online measurement technique in vehicles. Within this context, the focus in the research group is on the transfer of the EIS from the lab to vehicle batteries using in-house developed single cell sensors.
To enable online-EIS, a highly synchronous and precise measurement of current and voltage is crucial. For the current measurement, tunnel magnetoresistive (TMR) sensors offer a promising solution, as they are highly sensitive, low-interference and detect currents without contact. The presented differential connection of two TMR sensors further increases the measurement accuracy by reducing interference and detecting small signal changes more precisely. This behavior can be further enhanced with a proper designed current conductor.