Design And Implementation Of Lithium BMS Based On Active-passive Hybrid Balance

Lithium batteries are widely used in electric vehicle due to their high energy density,low self-discharge rate,and long service life.Hundreds of lithium batteries in electric vehicles are inevitably inconsistent.The inconsistency of the lithium battery pack will result in a significant reduction in the actual usable capacity,and even safety risks.Firstly,this paper analyzes the related technologies in the field of lithium battery equalization,including the equivalent model of lithium battery,the cause of inconsistency,the selection of equilibrium variables and the current main equalization method.Then,based on the existing equalization topology,this paper re-innovates and proposes a hybrid equalization topology which combines passive equalization and multi-transformer equalization topology based on flyback transform.Through the mixed equalization mode,the two equalization methods can combine their own advantages,and can make up for each other’s deficiencies,which can make them more valuable in practical application scenarios.After that,this paper introduces how to design the distributed--hybrid equalization management system based on the above topology design.In this paper,the distributed design idea is used to divide the system into different parts of the master communication unit,active equalization unit,information collection unit and passive equalization unit.The whole system shares a master communication unit and an active equalization unit.Each small battery group is separately installed with an information collection unit and a passive equalization unit.Each unit exchanges information through CANBUS.The entire battery equalization system communicates with the PC through Ethernet and NB-IOT,and the user can monitor the working state of the electric vehicle battery system in real time.In this paper,test experiments of each functional module of the system are introduced.Through the analysis of experimental data,the battery equalization system designed in this paper meets the design requirements.