Modeling And Simulation Of Charging And Discharging Characteristics Of MH-Ni Batteries

Issues about environment protection and energy sources security are focused on the automobile industry in recent years. Then Hybrid Electric Vehicle (HEV) emerges and becomes the focus and trend of the researches. The essential of the competition for HEV is the battery competition, how to ascertain the performance of batteries economically and fleetly has become one of the hotspots of each country. Performance of batteries represents in the final analysis State Of Charge( SOC), Since SOC of MH-Ni battery is influenced by many factors, such as temperature, electric current, voltage and so on, it is difficult to obtain ideal results by traditional methods. The application of modeling by using pond to analog battery, estimating the value of SOC is adopted. The research achievements and innovations in this paper are as follows:Firstly, the basic work principle and charging-discharging characteristics of MH-Ni batteries have been analyzed. MH-Ni battery is always the first choice of Hybrid Electric Vehicle (HEV) due to its advantages such as high Capacity, high Power Level, long life, and high performance. Since MH-Ni batteries have complicated performances in different working situation, how to estimate SOC precisely has become the main restriction factor for the development of HEV. SOC of MH-Ni battery is influenced by many factors such as discharging current,voltage, temperature, battery aging and so on. So forecasting and estimating SOC precisely are difficult jobs.Currently, the commonly used methods of forecasting SOC are showing as follows: ampere-hour method, Open-Circuit Voltage, and so on. Each method has its advantages and disadvantages. This paper has brought forward a new thought of modeling by analogy to estimate SOC through generally understanding the above-mentioned methods. Charging-discharging characteristics of MH-Ni batteries have been analyzed by analogizing pond model to battery model, making complex problems simple, thus comprehend the characteristics of the battery model of HEV macroscopically, making the result more precisely and the computing faster.The writer of this paper and her tutor have founded the mathematics model of analogy modeling, several charging-discharging experiments have been made about the model. Then identification and simulation about the experiments' datum has been implemented, rectifying parameters of the model time after time, then any single state of SOC can be gained during the charging-discharging process. In the end, the estimation result has been analyzed, it shows that the value of SOC can be attained conveniently, and it satisfied the requirement, brought a new SOC estimation methods for Battery Management System (BMS).