Research On Multi Channel Active Equalizationtechnology For High Power Lithium Battery

With the growing awareness of environmental protection and the ongoing exacerbateing of disposable energy crisis around the world, people begin to accelerate the pace of research in renewable energy. Because of high cell voltage, high specific capacity and low self-discharge, lithium battery is widely used in electric vehicle, distributed power generation, uninterruptible power supply, and some other related fields.High-power lithium battery pack is aimed primarily at the battery of electric vehicle(EV) or hybrid electric vehicle(HEV), and the battery capacity is 3 ~ 60 KWh or even higher. Due to the low single voltage of lithium battery, they are typically used in series. In order to get a power battery pack system with highercapacity, people tend to make 200 single cells or more batteries in series. In the course of the series, with the increase of the number of charge and discharge, the difference between the lithium battery cells will keep increasing, which restrict its safe and become a bottleneck of reliable operation. However, Equalization is intended to address security issues resulting from the life issues, overcharge and over discharge. Those problems are caused by the inconsistencies between the battery parameters. And equalization has turned into a focus in recent years.This paper analyzes the existing balanced topologies from the equalization rate, equalization efficiency and the complexity of equalization circuit. Besides, we also explain their respective applications. Then, we make an analysis on two key technologies in the battery management system: parameter detection technology and balance controlling technology. We propose an active equalization method of two-way multi-channel, which is suitable for master-slave architecture of high-power lithium battery pack. Based on the flyback converter, we design a proactive equalization module and the online detection module concerning voltage and temperature. The designed equalization module realizes the two-way flow between the cells and the battery energy, and the maximum equalizing current reaches 5A. What's more, the accuracy of voltage detection module is 2m V. At last, based on the developed battery management system, we conducte parameters test and balancing test. The results show that this system, with high efficiency balanced, can be used in high-capacity lithium batteries.