Research On Automotive Battery Multi-source Generation Model And Electrical-thermal Inconsistency

Promoting the use of new energy vehicles, especially electric vehicles, is an effective measure to cope with global energy shortage and environmental pollution. Power battery, the power source of the electric vehicle, is one of the key components of electric car. In order to extend the endurance mileage and improve the power performance of electric vehicle, power batteries are used in parallel. It aims at increasing the capacity and maximum working current of battery pack. However, due to the differences of manufacturing process and using environment, electrical and thermal inconsistency among single cores is inevitable in battery grouping use. The inconsistency not only reduce the battery charge and discharge efficiency, accelerating the attenuation of the battery, but also shorten the service life of power battery pack, and aggravate uneven cells generate heat and temperature distribution. Temperature is one of the main factors that have great impact on power battery performance, service life. The electric and thermal parameters of battery state are the main monitoring and control objects of battery management system, which reflect the electric work environment and affect battery working performance.Lithium-ion battery is widely used in electric vehicle because of its advantages in energy output, working voltage, service life, and other on. The paper takes lithium-ion battery for example, to find out how the initial electric inconsistency level, battery number and working current influence battery electrical parameters and thermal parameters variation and distribution characteristics. The research work is carried out from cell core, single cell and parallel battery group gradually.First of all, deeply analyze the heating mechanism of power batteries, and explain the importance and necessity of establishing lithium-ion battery multi-source heat generation model, after summarizing the study results done by domestic and foreign researchers. Carry out electric core and cell characteristics experiments, in order to obtain the resistance characteristics and open circuit voltage characteristics, and build the three-dimension heat generation model on the basis of experiment result. Analyze the heat transfer and heat dissipation characteristics of electric core and battery cell by finite volume method and heat balance thesis, create thermal effect model respectively, and verify the thermal effect models by temperature results in electrical core and battery cell constant current experiments. Electrical model of parallel battery group is built to study electrical parameters change law of every battery during charge and discharge work condition. UDF programs is written and loaded in FLUENT to realize separation control and loading of heat production rate on every heat source of every battery. The change law of heat production rate, temperature variation and temperature distribution characteristics are study on simulation results.The research results show that the three-dimensional multi-source generation model can present the actual use electrical core and single battery more actually. If the battery center is simplified to a uniform heat generating body, the temperature simulation result is lower than the actual temperature. During charging and discharging process, both the electrical parameters and thermal parameters change are very complex. Besides, they change drastically in the early and late of charging and discharging process, which is mainly caused by the resistance characteristics and OCV characteristics.