Thermal behavior of intelligent automotive lithium-ion batteries: Operating strategies for adaptive thermal balancing by reconfiguration

Abstract

Conventional batteries in electric vehicles face challenges due to multiple different cell-to-cell variations, e.g. voltage, SOC, capacity and internal resistance. These cell specific parameter and the temperature of the corresponding cell are significantly influencing each other. Thus, advanced thermal management solutions are urgently necessary, to achieve homogeneous thermal conditions in terms of aging. As a solution, a reconfigurable module prototype is presented and tested experimentally. Based on the prototype, a lumped thermal model of the intelligent reconfigurable battery module is developed, parameterized and validated using the experimental results. Subsequently, the model is used to investigate different strategies based on reconfiguration for thermal homogenization. A novel thermal operation strategy is introduced that adaptively adjusts the heat generation of each cell individually for thermal homogenization. Three distinct cases of realistic cell-to-cell variations and their thermal effects in a BEV module are investigated. Thereby, the fundamental trade-off by the system current increase and the interactions between thermal balancing and the SOC are discussed in detail. In all observed cases, the maximum temperature was reduced and the homogeneity of the modules was increased. Further aspects like the impact on the mean module temperatures and general strategies are discussed.