Fast Charging Control for Battery Packs With Combined Optimization of Charger and Equalizers

Effective fast charging is of great importance in the application of lithium-ion battery packs. In this article, a combined battery pack charging system is constructed by integrating the charger and cell-to-cell equalizers, which can excellently solve the cell imbalance problem in the battery pack. Based on this charging system, a fast charging control method is proposed to coordinate and optimize the current provided by the charger and the equalizing currents by formulating a constrained optimization problem with consideration of the battery pack's charging time, energy loss, and charging constraints. Next, a two-layer optimization strategy is designed to solve it, where a binary-search-based charging time region contraction method is adopted to determine the minimum expected charging time in the top layer, while the bottom layer utilizes the barrier method to search for the corresponding optimal charging and equalizing currents with the charging time given by the top layer. At last, extensive simulation and hardware-in-the-loop experimental results demonstrate the superior performance of the designed optimal fast battery pack charging control strategy.