Research on Alternating Equalization Control Systems for Lithium-Ion Cells Charging

Chuanwei Zhang,Jinpeng Liu,Yikun Li,Jing Huang,Zhan Xia

doi:10.3390/wevj12030114

Chuanwei Zhang, Jinpeng Liu + Show 3 more

Open Access

https://doi.org/10.3390/wevj12030114

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Abstract

Lithium-ion batteries which are used in electric vehicles cannot be charged to their maximum capacity at the end of the charging period, a situation which is caused by inconsistency between the battery cells. This paper takes the 18650 ternary lithium battery as the research object and proposes an alternate equalization control system in the charging process. This system takes SOC consistency to be the equalization variable. Through controlling the relay, this system realizes the alternate recombination between different batteries in order to form a series battery group for charging, which achieves the goal of SOC equalization of the entire battery group. The simulation result of charge equalization, based on Matlab/Simulink, shows that at the end of the charging simulation, the SOC inconsistency of the battery group reduced from 10% to 1%. Finally, an experimental platform was built in order to verify the experiment. During the charge balance experiment, the maximum SOC inconsistency between the batteries reduced from 1.542% to 1.035%. The SOC inconsistency at the end of charging reduced from 1.214% to 0.8%, which represents an improvement of the equalization effect of the control system. The experimental results are consistent with the simulation results, which proves the effectiveness of the system’s ability to control the battery SOC balance during the charging process.

Highlights

Lithium-ion batteries have the advantages of a high energy density, low self-discharge, and long cycle life and have been widely used in various energy storage devices [1].single cells form battery packs in series and in parallel to increasing the voltage and energy requirements of the energy storage system [2]
Battery equalization technology is an effective method to solve the inconsistency of battery packs [6]
According to different energy transfer modes [7], battery equalization technology can be divided into passive equalization and active equalization

Summary

Introduction

Lithium-ion batteries have the advantages of a high energy density, low self-discharge, and long cycle life and have been widely used in various energy storage devices [1].single cells form battery packs in series and in parallel to increasing the voltage and energy requirements of the energy storage system [2]. Due to the differences in manufacturing processes and working environments, there are inconsistencies between batteries [3]. This inconsistency can expand with the use of batteries, resulting in a “Barrel. Passive equalization means that high-power batteries dissipate excess energy in the form of heat through dissipating components [8,9]. This method’s structure and control strategy are straightforward, but the passive equalization does not make the most of the energy, resulting in a waste of energy

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