Modeling and experimental validation of series connected battery pack modules

Abstract

For applications such as electrified automotive powertrains, which require high power density and operating voltages, the lithium-ion battery is an ideal candidate. When individual batteries are combined into packs, a battery management system is needed to safely operate packs consisting of hundreds of cells in series and parallel configurations. While much attention has been given to modeling and analysis of single cells, there has been less attention given to modeling and analysis of pack configurations regarding voltages and currents in the strings that make up the pack. Such analyses have an impact on investigations regarding pack balancing. Moreover, relatively little research has appeared in the open literature regarding experimental validation of models with regard to voltage and current characteristics in pack configurations. In this article we present a dynamic model for a lithium-ion series battery pack based on the voltage-current relationship of individual cells in various operating scenarios such as charge balancing. Resulting models are validated in the lab using a special purpose battery pack by comparing the simulated pack model with the bench top battery pack.