Enhancing the Cell Impedance Estimation of a Lithium-Ion Battery System with Embedded Power Path Switches

Estimating the impedance of lithium-ion cells is of increasing interest, especially on-board electric vehicles to enlarge their diagnostic capabilities. Therefore, an innovative approach for cell impedance measurements is presented in the context of intelligent battery management systems. Hereby, the load current excitation injected by the electric powertrain is switched by power MOSFETs. This quasi-active impedance spectroscopy can be performed with a reconfigurable battery system to shape the excitation signal without further hardware. A broadband data processing algorithm that handles both pulsing and non-pulsing data in the frequency domain is introduced. It generates impedance data of high quality while reducing the computational efforts compared to previous implementations. To evaluate the proposed methods under real world driving conditions, an experimental setup that emulates the application within a traction battery system is constructed. The obtained measurement results are in great accordance with those of reference laboratory equipment.