Simultaneous Thermal and State-of-Charge Balancing of Batteries: A Review

The battery pack lifetime is severely affected by the State-of-Charge (SOC) and thermal imbalance among its cells, which is inevitable in large automotive batteries. In this review paper, the need of simultaneous thermal and SOC balancing is emphasized. Thermal and SOC balancing are two tightly coupled objectives. However, we argue here that it is possible to achieve these simultaneously by using a balancing device that enables the non- uniform use of cells, optimally using the brake regeneration phases and load variations in the drive cycle, and exploiting cell redundancy in the battery pack. The balancer must provide extra degree-of- freedom in control by distributing a large battery pack into smaller units to enable an independent cell/module-level control of a battery system.