Optimization of LIFEPO4 Battery Pack for Electric Vehicles Application Using Active Balancer

Abstract

Cell-to-cell imbalance in series-connected LiFePO4 packs limits usable capacity and can introduce avoidable balancing losses, particularly when equalization relies on dissipative methods. This study quantifies the impact of adding a bidirectional active balancer to an electric-vehicle LiFePO4 battery pack that is otherwise managed by a Battery Management System (BMS). Two experimental configurations were evaluated under identical charge-discharge cycles: (1) BMS-only operation and (2) BMS operation combined with an active balancer (balancing current capability up to 5 A) that redistributes charge from higher-voltage cells to lower-voltage cells. Cell-voltage and pack-parameter data were acquired via the BMS communication interface using a Raspberry Pi, stored in a database, and visualized in real time through a Node-RED dashboard, enabling synchronized, cycle-by-cycle inspection of equalization behavior. Performance was assessed using charge-discharge coulombic efficiency together with the reduction in cell-voltage spread during charging and discharging. The measured coulombic efficiency with BMS-only operation is 87.50%, indicating significant loss during equalization, whereas adding the active balancer increases coulombic efficiency to 99.55% (a 12.05% improvement) and produces substantially tighter voltage uniformity. The results demonstrate that active balancing can markedly reduce balancing losses in LiFePO4 packs while providing a reproducible instrumentation workflow for laboratory and training use.