SOC Estimation Algorithm Of Lithium Batteries For Electric Vehicle And Research Of Uniformity Of Battery Strings.

Traditional engine vehicle development confronts with severe challenges, because of the increasingly serious energy and environmental pressure. When the retail price of gas get into"8 yuan"era , Energy-saving and environmental protection will must become new goal of vehicles development. Therefore, EV(electric vehicle) have got rapid development, but Power battery's performance and costs has become a key factor in the promotion of EV。Power electrical source is the main energy storage element of electric vehicle. So the performance of batteries influences directly on vehicle's performance. And the batteries of costs is accounted for half the price of EV, therefore, research on the battery is necessary.①Firstly, the trends of development of electric vehicle, application of the Power battery problems,the basic characteristics of battery is introduced in this paper. Then, test content and test process of the batteries are carried out.②Based on the performance experiment of batteries, the evaluation method of State of Charge(SOC) in lithium-ion batteries is researched. And a new evaluation method of SOC is investigated.③With the model of PNGV battery, the method of SOC based on open-circuit voltage was brought forward considering the temperature effect on the parameters of the equivalent battery model .④By lithium-ion battery charge and discharge characteristics, and power estimation, assessment of the battery pack can be a good difference. Based on the test of the battery charge and discharge cycle life and battery decay causes inconsistency, and then single battery voltage detection circuit to know the working status of single cells, and then analyzes consistency of the battery pack⑤A simulation model were set up based on Matlab/Simulink and obtained the parameters of the model by the lithium batteries charge-discharge test and HPPC test . Simulation and test result show that the PNGV model is very precise and can simulate the battery characterizations of charge and discharge as well. The cumulative error and inaccurate estimation of the initial value by the ampere-hour(AH) approach can be effectively avoided by the estimate method of SOC based on open-circuit voltage.And the estimation value of SOC can be kept highly precise, and the SOC error is less than 5%. The results show that the estimate method meets requirements.