Fundamentals and Applications of Lithium-ion Batteries in Electric Drive Vehicles

6Evaluation and Equalization of Battery Consistency

The evaluation and equalization of battery consistency is the core of the battery group application technology, directly affecting the batteries’ safety and efficiency. There is much literature that discusses battery consistency evaluation methods, and a variety of equalization circuits have been proposed. All are based on the use of the voltage difference of the batteries to evaluate the battery consistency and implement the equalization controls, but the previous evaluation methods cannot effectively detect inherent differences in the batteries, which may cause degradation of equilibrium effects. Therefore, it is very difficult to control such factors as the capacity, volume, cost, and heat dissipation of the battery online equalizers. Offline equalization increases the maintenance workload of the battery and eventually hinders the large-scale popularization and application of electric vehicles. Based on the battery modeling, parameter identification and state estimation mentioned above, we will discuss the mechanism leading to battery inconsistency and its influence on the battery performance, consistency evaluation index selection, consistency quantitative evaluation methods, and equilibrium problems, then propose a more reasonable equalization control strategy which can effectively improve the utilization efficiency of the equalizer, reduce the equalizer's design capacity, provide a theoretical basis and data support for battery ...