Protocol‐Aware Threshold‐Tuned Passive Balancing for Lithium‐Ion Battery Packs: Experimental Validation of Voltage Uniformity and Thermal Safety

ABSTRACT Maintaining voltage uniformity and thermal stability in series‐connected lithium‐ion battery packs is essential for ensuring performance, safety, and cycle life, particularly in electric vehicle applications. This study presents an optimized, threshold‐based switched passive balancing strategy implemented through MOSFET activation. The objective is to evaluate balancing effectiveness under both constant current (CC) and constant current–constant voltage (CC‐CV) protocols and to determine the optimal activation scheme. The proposed system was experimentally validated on a six‐cell (21.6 V, 2.6 Ah) Li‐ion module. The balancing logic dynamically initiates charge redistribution when cell voltage disparities exceed a defined threshold ( V min ). Results show that under CC charging, balancing significantly reduced voltage deviation while maintaining comparable charge duration. Under CC–CV charging, delayed balancing activation during the low‐current CV phase led to improved charge equalization, sustained voltage alignment across cycles, and enhanced thermal stability. In all cases, power dissipation was maintained below 1 W, confirming the energy‐efficient operation of the design. Unlike conventional passive balancing, we experimentally demonstrate a protocol‐aware, threshold‐tuned strategy that delays activation into the CV phase to minimize heat while maximizing equalization. The design maintains total dissipation below 1 W and sustains cross‐cycle alignment under CC–CV, establishing a practical operating envelope for EV packs. Compared to conventional fixed‐threshold passive balancing, the proposed protocol‐aware scheme achieves lower voltage deviation, sub‐1 W power loss, and superior thermal stability during CC–CV charging. Unlike prior passive balancing schemes, this work provides the hardware‐validated, protocol‐aware, CV‐delayed balancing framework, experimentally proven to sustain Δ V ≤ 45 mV across 50 cycles with < 1 W dissipation. This establishes a new benchmark for scalable battery management system (BMS) deployment in next‐generation EV and grid storage systems.