Research On The Charging Planning Method For The Whole Life Cycle Of Lithium Batteries For Vehicles

With the rapid development of the new energy automobile industry,lithium battery has become the core of the current energy storage part of electric vehicles due to their advantages of low self-discharge,long cycle life,high-energy ratio,and no pollution.The traditional charging method adopts a single charging scheme for the whole life cycle of the lithium battery,which causes many problems such as low charging efficiency,short service life,and unsafe charging of the lithium battery.In the dissertation,the lithium battery life cycle charging scheme was researched and the charging curves of different life stages were planed.The main contents and innovative work of this dissertation are as follows:1.The working principle of lithium battery was researched,and several common equivalent circuit models of lithium battery was analyzed.Based on the advantages and disadvantages of each model,the second-order RC equivalent circuit model was selected and established,and the state equation was derived.Based on this model,the basic characteristics of the lithium battery were researched.2.The parameter identification and SOC estimation of lithium batteries were researched.Firstly,the relationship between open circuit voltage and SOC was obtained through experimental data.Then several parameter identification methods were studied.Finally,the parameters of lithium battery equivalent circuit model were identified by forgetting factor recursive least squares method,and the identification result of the parameters was obtained through experiments.According to the obtained parameters,the extended Kalman filter algorithm was used to estimate the SOC of the lithium battery.And the accuracy and feasibility of algorithm were verified by the simulation experiments.3.Lithium battery life cycle division and charging curve planning research.According to the relationship between the number of battery cycles and SOC,the life cycle of lithium battery was reasonably divided into three life stages.The theory of Mas charging curve was studied and analyzed,and the influencing factors of charging acceptance rate were qualitatively researched.Combined with the traditional charging method and influencing factors,the charging planning method for the three life stages of lithium battery was proposed.4.Design and experimental analysis of lithium battery life cycle charging curve planning system.The TMS320F28335 was used as the main controller to build the hardware platform.The Microsoft Visual Studio was used to design the upper computer charging monitoring system.The experimental platform could monitor the battery parameters and charging process,and complete the tracking of the lithium battery life cycle charging curve planning and charging process.The lithium battery life cycle charging planning method proposed in this dissertation was verified by experiments,and the tracking curve and test of the charging curve were carried out.The experimental results showed that the lithium battery life cycle charging curve planning method proposed in this dissertation has engineering feasibility and feasibility.