| The power battery,also called the rechargeable battery,refers to the battery that can be activated and reused by the active material after the battery is discharged.Hundreds of single-cell power batteries are packaged in series and in parallel to form a battery pack.The battery pack provides energy for electric vehicles and it is one of the core components of electric vehicles.In the process of using the battery pack,the performance of batteries usually have the problem of inconsistent,which is mainly caused by two aspects.The batteries that cannot be eliminated due to factors such as materials and processing techniques in the manufacturing process are inconsistent;The environment and the performance in which the cells are used in the battery pack is inconsistent.Increasing the consistency of a single cell mainly depends on improving the battery production process and improving battery sorting method.In order to improve the consistency of the performance of each battery in the battery pack.People mainly use the battery management system(BMS)to monitor and manage the battery,prolong the consistency of the battery and suppress the inconsistency of the battery.Existing battery sorting methods are inaccurate in sorting standards and sorting parameters.The dynamic change of the battery during use cannot be reflected,and the state management of the battery and the estimation of the real state of the battery are not well solved.In this thesis,through battery experiments,the main factors affecting the initial performance consistency of lithium-ion batteries are researched.The influence of different factors on battery attenuation is analyzed.Based on these two points,a battery sorting method is proposed.The efficiency and life span influence of the battery with different performances in the series and parallel of the battery pack was analyzed and discussed.A battery management system(BMS)was developed,the use effect of BMS in the battery pack was analyzed.The specific work is as follows:1)Explore the main factors affecting battery performance.The main factors affecting battery performance were studied through experiments.On the basis of summarizing the effects of various factors on battery performance,we choose the battery capacity,battery internal resistance,battery charge and discharge efficiency,open circuit voltage and self-discharge rate 5 parameters as sorting variables.By setting up a series of control groups,the performance test of the battery was carried out,and the decay rate of the battery capacity and the change of the charge and discharge efficiency of the battery under different conditions were analyzed.The results show that the battery charge and discharge efficiency and battery temperature have a greater impact on battery performance.2)Optimized power lithium-ion battery sorting methodThe separation method of lithium-ion battery is studied.We use system cluster analysis and battery charge and discharge curve characteristics as a means to classify the battery.The effects of series-parallel battery packs on battery performance were studied.Experiments show that the performance of sorted battery packs is better than that of unsorted battery packs.3)Development of battery management system.A battery management system was developed.The battery management system can be used to monitor and control charge and discharge of the battery pack.The results show that the system can manage the battery pack well. |
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