Feasibility of EIS on Module Level Li-ion Batteries for Echelon Utilization

The exponential growth in electric vehicles causes similar growth in retired batteries, resulting in a need to evaluate these batteries for possible use in other applications. Methods for fast health characterization are still challenging for batteries. So far, electro-chemical impedance spectroscopy as a frequency domain measurement technique has been mainly used for this purpose at the battery cell level. This paper aims to evaluate the feasibility of EIS on the module level, to see whether it allows obtaining the module’s practical electrical equivalent circuit model (ECM) beyond cell-level modeling. To this end, ECM parameters derived from EIS measurements on cells are compared with those from modules made from these cells. The results show a clear correlation between measuring the EIS on the cell level and the module created by connecting the same cells. This provides a first evidence for the usefulness of conducting EIS measurements at module level with an acceptable range of accuracy and consistency with the results obtained from the individual cells.