Experimental Characterization of Li-Ion Battery Resistance at the Cell, Module and Pack Level

Nowadays, a large variety of lithium-ion battery (LIB) configurations are being developed in order to meet the specific requirements of different applications, e.g., for battery electric vehicles or stationary energy storage. One characteristic parameter of LIBs is their internal resistance, as it influences the system's power capability and heat generation. However, determining the resistance of a battery pack is not trivial, since it is dependent on many intrinsic and extrinsic influencing factors. In this work, influencing factors on the resistance of 18650 cylindrical cells and large-size prismatic cells are quantified experimentally by means of direct current (DC) pulses and electrochemical impedance spectoscropy (EIS). Furthermore, challenges involved in characterizing the resistance on higher system levels are addressed by investigating battery modules and packs of a research vehicle built out of small cylindrical cells and a series vehicle with large prismatic cell architecture. Finally, based on experimental findings, the authors derive implications for battery modeling that make it feasible to choose the suitable modeling depth and evaluate the numerous different available cell types and system configurations efficiently for their suitability for different battery system concepts. The data for all evaluated resistances is provided as supplementary material [1].