Research On Battery Condition Monitoring System For Electric Vehicles

The development of the global automobile industry has been plagued by the problems of energy and environment. So in recent years, people are constantly working to research that clean and accessible energy replaces the traditional fuel as power automobile. And because of the advantages of energy saving and emission reduction, the pure electric vehicles for the representative of the new energy vehicles attracts more attention of a vast number of car manufacturers. Battery monitoring system is a hot spot in the research of electric vehicle, as a key technology of electric vehicle, its development for electric vehicle power battery group of safe use and effective management plays a vital role.First, the basic functions of battery monitoring system are described briefly, and the research status at home and abroad of battery monitoring system is introduced in detail in this paper. By consulting the literature to understand the main power source of the existing electric vehicle, the system is determined to monitor the object? lithium-ion battery. And the parameters of the two order RC equivalent circuit model of battery are obtained by using the model parameter identification.Secondly, according to the current research focus of battery monitoring system, the two directions of battery SOC estimation and battery equalization are studied in this paper. The battery SOC estimation is an important basis for judging the operating status of the battery. And by introducing and comparing several methods used widely in SOC estimation at present, a estimation method based on square root unscented Kalman filter using spherical transform is proposed. The complexity and accuracy of the derivation process is improved by this method. And Battery equalization is the solution of the problem of battery inconsistency. Because the disadvantages of low efficiency and large energy consumption are existed in the current battery equalization method, a voltage equalization method for battery based on CUK bidirectional converter is studied.Then, DSP28335 is used as a control chip in the designed battery monitoring system. In hardware, the single battery voltage acquisition circuit, current acquisition circuit, temperature acquisition circuit, two order filter and sampling circuit, protection circuit and communication circuit are designed. And in software, the main program, data acquisition module subroutine, battery condition judgment subroutine, EEPROM read and write function subroutine, CAN communication subroutine, interrupt service subroutine and battery equalization subroutine are designed.Finally, the data acquisition function of the battery monitoring system is tested, and the obtained data are compared and analyzed. At the same time, the SOC estimation method and the battery equalization method are simulated to verify the rationality and reliability of the design of the battery monitoring system.