Precise High-Frequency Impedance Measurements of Cylindrical Battery Cells for Electric Vehicles

Characterization of cells is a key step in the design process of battery packs. Measurement-based models allow simulations of battery packs and electric vehicles in the early design stage reducing development time and cost. This paper demonstrates a method for measuring battery cell impedance with higher precision and wider bandwidth using vector network analyzer in the frequency range from 1 MHz to 680 MHz. A printed circuit board (PCB) adapter is developed to connect the battery cell to coaxial cables and allow for repeatable results. Inductance dependence on state of charge and inductance dependence on axial position of the probe are presented. Proposals for further improvements are given.