| Nowadays, various countries in the world gradually pay attention toenvironmental protection, and the concept of having a green and healthy workenvironment becomes more and more welcome for today’s city people. At thesame time, the shortage of non-renewable oil energy and deterioration of theenvironment lead to the rapid development of electric vehicle which has theadvantages of environmental protection and energy saving. And the powerlithium battery is becoming the main member in the power battery of electricvehicle. So study of its charging technology has great significance at present.Firstly, this paper summarizes the development status of electric car industryat present, lists the main problems of lithium battery in technology, anddetermines the charging technology as the main research content of this article.Secondly, analyzes the characteristics of power lithium batteries, includingperformance comparison of all kinds of power batteries, the working principle oflithium batteries, characteristics of charge and discharge, best charging curveand the polarization characteristics of the battery, which lay the foundation forsubsequent studies on charging technology. Thirdly, on the comparison of fourkinds of conventional charging method, a variable current charging method isproposed in this paper. It is divided into three stages: small current tricklecharging, piecewise constant current charging and pulse charging. Using thecapacity control method to control the charging current in the stage of piecewiseconstant current charging, which makes it close to the optimum charging curve.The method of charging control technology is designed to control the full chargestate in the end of charging. The lithium battery charging circuit and PNGVequivalent model of lithium battery are designed in Matlab/Simulnik software todo the simulation of variable current charging. At the same time, in order toverify the superiority of this method, compare with other three typical kinds ofcharging method is done. Fourthly, this paper proposes a variable resistancebalance control technology through the analyzing of the equalization controlmethods. It uses digital coding method to design digital variable resistor, and sets up digital variable resistor model in Matlab/Simulnik software platform. Inthe simulation, the control program is compiled through S-function, and sixmonomer lithium batteries, whose voltage is different, are applied to balancecontrol to makes the battery voltage achieve consistently. Through thesimulation, the feasibility of variable resistance balance control is verified.Fifthly，the paper chooses a microcontroller produced by ATMEL companyas the control chip to set up a intelligent charging experiment platform. In theplatform, a2200mAh lithium-ion polymer battery is selected as the researchobject. And variable current charging, variable resistance balance control andvoltage negative growth rate control method are verified. The charging data isrecorded to verify the feasibility of these methods, the anticipated target of theresearch is basically achieved. Finally, the research contents of this paper aresummarized and the future research prospect is analyzed. |
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