Research And Implementation Of Equalization Technology For Power Lithium Ion Battery Pack

As the green cars, the electric-vehicles have been getting more and more attention from people. Power battery is considered as the main energy of electric vehicle, It is very important to research the power battery technology. In recent years, a lot of researchers of related companies and universities devote most of their time and energy to power battery research and Battery Manage System(BMS) at home and abroad. Lithium ion battery has been widely used as energy of electric vehicle for its superior performance. But the single lithium ion battery can not provide enough voltage and capacity to meet electric vehicle, so the lithium ion batteries must be connected in series into a pack. There is a inconsistency problem between single cells in battery pack, and serious inconsistency problem will severely degrade the performance and the cycles of battery pack.The inconsistency of battery pack mainly exist in battery internal resistance, capacity, state of charge(SOC), voltage, temperature and so on. This thesis deeply study the equilibrium technology of lithium ion battery pack, and design an adaptive equalization control system, which is made up of equalization circuit and balance control strategy. According to the energy transfer mode, equalization circuits can be divided into energy transfer between cell and battery pack, energy transfer between adjacent battery cells and energy transfer from the highest battery cell to the lowest battery cell. A kind of non dissipation of energy equalization circuit is designed in this article, which can make energy transfer from battery pack to a battery cell and from the highest cell to the lowest cell, and which can achieve a equilibrium effect that can decrease high battery's energy and increase low battery's energy. A kind of efficient equalization control strategy, which can comprehensively consider the working voltage and the state of charge as an equilibrium target, and which can automatically judge the inconsistency state of battery pack to determine whether to decrease high battery's energy or increase low battery's, and which can automatically configure equilibrium parameters and reasonably set the condition of opening equilibrium to select the optimal equilibrium way and equilibrium time.Equalization control system is a sub system belongs to the battery management system(BMS). A kind of battery management system has been designed according to the equalization control system that has been designed at first in this thesis, which includes hardware design and software design. Then the schematic and PCB are drawn, and a human machine interface is designed. A lot of equilibrium experiments have been performed on the experimental platform of battery management system. Then analyze the experimental data to draw correct conclusions.