Enhancing Automotive Batteries: Onboard EIS with a Dedicated Converter Solution

Abstract:
Battery degradation is limiting electric vehicle (EV) market growth, since high costs and uncertain lifespan impact consumer confidence. Electrochemical Impedance Spectroscopy (EIS) offers a valuable contribution to improve the battery health estimation, as it can provide insights into the electrochemical response of battery cells. Typically, EIS is performed after disassembling the battery and under laboratory conditions. However, onboard EIS remains a challenge. This paper analyses the EV architecture and defines voltage and current sensing constraints to present an onboard centralized galvanostatic EIS system with a dedicated converter. The system is designed to operate across a wide frequency bandwidth by using a proportional-resonant controller. The converter operation is validated using the battery specifications from the Volkswagen ID.3 and the BYD Seal RWD. The EIS measurements performance is proved using the equivalent cell model (ECM) of a Molicel INR 21700-P42A in a Nyquist plot. Finally, system’s operation conditions to be integrated into the existing EV architecture are defined to ensure reliable EIS results.