Design Of Battery Charging System For Electric Vehicle

A large number of pollutants are created due to the long-term use of fossil fuels,leading to environmental degradation,climate warming and other issues.Countries around the world are studying new energy to replace traditional fossil fuels.The research result of lithium battery which applied to electric vechicles are excellence.The research of safe system and the efficient charging technology is great significance.Firstly,the development status of electric vechicles industry and its history is summarized in this thesis.The problems of low charging velocity,poor safety of charging and discharging are listed.Promotion and popularization of electric vehicles are hindered by these technical bottlenecks.Secondly,the characteristics of lithium battery are introduced,which contains the best charging curve and polarization characteristics of battery,as the follow-up lithium battery charging system and charging technology design basis.In order to meet the large-capacity energy storage and highpower output,the single lithium battery must be packed to manage,while the internal structure is encapsulated and provide the interfaces for external system.And then the ideas of extended and maintenance are put forward.For matching the lithium batteries group,a charging system is designed to implement charging management.Thridly,the lithium battery charging technology are researched,includes charging method,detection method of auto-off after full charged and technology of balancing control.To improve the charging speed and efficiency,an improved phased charging method is proposed,which uses variable current intermittent charging method to replace the constant current charging method and uses pluse charging method instead of constant voltage charging method.In order to determine the full charged status of battery group,an auto-off after full charged detection method which based on rate of voltage change is raised.Aim at ensure the consistency of lithium batteries packed charging,an improved balancing control technology of resistance is raised.This technology utilizes power switch gating variable resistor array to consume excess energy.After that,the batteries will achieve balanced control.Finally,a system experiment platform is set up,a comparative experiment is designed and the content of this thesis is analyzed.The charging velocity of improved phased charging method is increased by 42% than the traditional three-stage method.The relative error of the full charged is reduced to-2.6% by the voltage change detection method of auto-off after full charged.The relative error of battery terminal voltage difference in module is controled within ± 0.13% because of variable resistance equalization control method.The results of the three experiments all achieves the expected results,which proves the feasibility of the scheme.At the end of the thesis,the research contents are summarized,and makes a prospect for future research work.