An online health-conscious enhanced charging and active balancing strategy for lithium-ion battery packs

Abstract

As with many other applications, the need for an improved charging strategy with an emphasis on the health of the cells is increasingly important for the optimization of automotive and robotic systems. This paper introduces a novel method of managing the anode potential vs Li/Li+ of a lithium-ion battery pack using a 3D map based on experimental data and a physics-based model. This map, along with a SOC trajectory formulation, is the basis of the health-conscious enhanced charging (HCEC) strategy introduced in this study. This study also functionally combines HCEC with active balancing to ensure that all modules are quickly balanced, and the useable capacity of the pack is maximized. It was observed, using the generated 3D map, that the anode potential of the manufacturer-recommended CC-CV charging process is maintained in the safe region, but in an unoptimized region for the full length of the test. In contrast, the proposed strategy optimizes the anode potential in the safe region – resulting in a 16.3% charge time improvement. Likewise, the use of the active balancer increased the useable capacity of the pack by 5.3% from a 10% initial SOC deviation range compared to passive balancing.