Integrated Strategy for Optimized Charging and Balancing of Lithium-Ion Battery Packs

During fast charging of lithium-ion batteries (LIBs), cell overheating and overvoltage increase safety risks and lead to faster battery deterioration. Moreover, in conventional battery management systems (BMSs), the cell balancing, charging strategy, and thermal regulation are treated separately at the expense of faster cell deterioration. Hence, this article proposes an optimized fast charging and balancing strategy with electrothermal regulation of LIB packs. Therefore, the power dissipation constraints of passive balancing (PB) are introduced in the proposed integrated optimal framework, and cell balancing is achieved by bypassing the extra charging current. The electrothermal model of the cells, along with a battery pack formed by a string of cells, is implemented. Extensive experiments are carried out to identify the coefficients for the lithium-ion cell model, that is, Samsung-INR18650-20R, and the charging current trajectory as well as the balancing signals are generated with model predictive control (MPC). The pack-level simulations and experiments show that the proposed algorithm maintains the electrothermal boundaries throughout the charging process, increasing the safe charge acceptance of the battery pack.