Design And Research Of Active Equalization System For High Capacity Battery Pack

High-capacity battery,as an important component of electric vehicles and high-energy storage,determines the overall performance potential of the system.However,without external interference,the difference in battery characteristics of the same batch caused by different battery batches,battery production processes and aging loss,etc.,will constantly magnify over time,thus seriously affecting the total capacity and service life of the system.Therefore,how to reliably,quickly and efficiently reduce or even eliminate the difference between batteries is of great significance for the application of high-capacity battery packs.This paper,after comparatively analyzing the electrochemical and equivalent circuit model of high-capacity battery and the State of Charge(SOC)estimation method,adopts the Extended Kalman Filter(EKF)based on the model of Dual Polarization(DP)to estimate the SOC of the battery,judges the model accuracy through simulations and experiments,and verifies the SOC estimation effect of EKF by simulations.An active equalization system is designed at the cell level.By adopting the integrated chip solution based on LTC6811 and LTC3300,a peripheral circuit is built to realize the battery active equalization system which includes voltage,current and temperature detection(the peak value of the active equalization current is up to 16.67A).And the balance effect and actual efficiency between the cells is verified through experiments.The corresponding balancing strategy is proposed for the operation characteristics of high-capacity batteries in the state of discharge,charging and standing,to improve the pertinence of the system and the overall operation effect of the battery pack.And the feasibility and effectiveness of the strategy is verified through experiments.A scheme of balancing the crossover high current is presented for the active balancing between the cells of the liquid metal battery which is rarely studied for now.And the feasibility of the scheme is verified by simulations and experiments.