Adaptive Thermal Control of Cell Groups to Extend Cycle Life of Lithium-Ion Battery Packs

Abstract

We present a novel approach for a battery management system in which adaptive thermal control is employed to balance the capacities of individual groups of cells within a lithium-ion battery pack. Maintaining capacity balance within the battery pack in this manner can significantly extend its cycle life. We explore the physical implementation of this concept and demonstrate that it is a viable way to extend the life of battery packs. The experimental setup consists of three pairs of cells connected electrically in series and supplied with coolant flow from a chiller. All cells are initially in capacity balance and are cooled uniformly for the first 50 fast charge/discharge cycles. Subsequently, cooling is halted to specific cell pairs to deliberately unbalance their capacities. Finally, cooling is selectively restored to correct the capacity imbalance between the cell groups by the end of 100 charge/discharge cycles. These results suggest that adaptive thermal control can be used effectively to maintain capacity balance within the battery pack.

Keywords

• lithium-ion batteries
• battery management system
• thermal management system
• battery degradation
• grid storage
• electric vehicles