On the Feasibility of EIS-Based Online Battery Monitoring Assessed in Automotive Grade Environment

Online diagnosis of lithium-ion battery in electrical vehicles is of paramount importance to assess battery performance and degradation, thus improving the operation efficiency and preventing faults. This work investigates the feasibility of implementing electrochemical impedance spectroscopy (EIS) for the online monitoring of battery cell state parameters, such as the the state-of-health (SoH) and the cycling ageing, in the framework of common industrial procedures for automotive applications. SoH and ageing cell are assessed by typical laboratory tests in automotive grade environment, together with EIS measurements performed both at specific check points and online, during the charging/discharging tests involved in the procedure. The battery impedance measurements are conducted by means of a custom-designed EIS-based sensing system, implementing a multi-band multisine excitation strategy for fast measurement time (as required by online EIS) while preserving good accuracy. Compared with automotive laboratory instrumentation, the online multi-band multisine EIS demonstrated to be suitable for the real-time monitoring of both the battery impedance evolution and the ageing trend.