Extraction of Single Cell Impedance From Battery Module Measurement by Simulation-Based De-Embedding

Batteries are a fundamental part of many modern electric systems. As a result, battery modeling is increasingly important for the prediction of signal and power integrity (SIPI) as well as electromagnetic compatibility (EMC). Conventional battery module modeling requires knowledge of the integrated cells first, which is usually obtained by measurement on single cells. However, if individual cells are not accessible, the single cell's impedance needs to be extracted from measurement of the complete module. This work describes two solutions to this problem, which are both based on 3D electromagnetic (EM) simulation of the battery module with surrogate cell models to obtain S-parameters, which describe coupling effects inherent to the modules' geometry. By either fitting of the simulated module impedance to the measured data on circuit schematic level, or by numerical multiport de-embedding, the single cell impedance is extracted. Considered frequencies range from 9 kHz to 1 GHz.