Study On Life Estimation And Optimization Of Lithium-ion Power Battery For Extended Range Electric Vehicle

Extended range electric vehicles(EREV) become a research hotspot with the advantages of high saving rate, not being limited by the range, and thus being considered to be the best transitional products between fuel vehicles and pure electric vehicles. As a key component of EREV, lithium-ion power battery’s performance and life have a major impact on the vehicle performance, economy and safety. The battery life state is one of the most important parameters of EREV vehicle use and control, so it’s significant to study the power battery life combined with EREV vehicle.This subject takes the self-development of a lithium ion battery system for a self-owned brand EREV as background, studied the lithium-ion batterie’s characteristics of different working conditions and environment, established an equivalent circuit mode for lithium-ion batterie, and fitted the cycle life of the EREV lithium-ion batterie system with data of the life test. In order to extend the battery system’s lifespan, studied the main influencing factors of the battery life attenuation, put forward the corresponding optimization control strategy. The main research contents:1. Studied the work requirements and performance characteristics of lithium-ion power battery system for EREV, primarily include the research of EREV’s dynamic structure, work characteristics and energy control strategy, the work principle and pack technology of lithium- ion battery, and the work requirements and performance characteristics of battery system for EREV;2. Analysed the existing battery model, established the two order RC equivalent circuit model of lithium-ion battery for EREV, and proposed the parameter identification method;3. According to the requirements of EREV, with the EREV lithium-ion battery cell and battery pack as object, carried out the charge/discharge test in accordance with the lithium-ion battery test standard, analysed the test data to study the main electrical properties;4. Performed the EREV lithium-ion battery system cycle life test, then got the relationship between charge/discharge capacity and cycle number. Fitted the life curve of lithium-ion battery system based on Matlab genetic algorithm toolbox, and calculated the cycle life of the battery system according to the fitting formula;5. Put forward battery life optimization control strategies combined with the characterist- ics of EREV, such as optimizing the air cooling system, improving consistency, and optimizing charging strategy.This subject has important implications for accurately predicting the battery life, planning EREV use reasonably, improving the economy of EREV, and speeding up new energy vehicles popularization.