Research And Design Of Battery Manage System For Pure Electric Vehicle

In recent years, with the dual advantage of energy-saving and environmentally friendly, electric vehicle industry is increasingly subject to the attention of the national and enterprise under the increasing pressure of energy and environmental issues. As the main energy carrier and power source, power battery is an important part of the pure electric vehicle, which directly affects the service performance and manufacturing cost. Working as a real-time monitoring tool of battery power status, to ensure reliable operation of the battery safety, and to extend battery cycle life, the battery management system is of great significance to reduce the electric cost of car use and to improve the security of the electric vehicle.Choosing lithium iron phosphate battery and colloidal maintenance-free lead-acid battery as the test objects, the subject respectively researched on charge and discharge characteristics, temperature characteristics. The results show that there is a big voltage difference between single cell of the two above batteries during charge and discharge process, especially at the late of process, that is, Imbalances exists between the single cell within the battery pack. Generation of imbalances is often accompanied by the reduction of the effective capacity of the battery pack, single battery undercharge and overcharge, and so on, which not only reduces the efficiency of the battery pack, and also shortens the cycle of life. For the phenomenon of imbalances, the research designed a type of resistance dissipative charge balance system, and studied the charge and discharge test. The results showed that the charge balance system can effectively improve overcharge and undercharge problems of single cell at the late charge process, improve the consistency between the single cells and increase the effective capacity of the battery pack, which is of great significance to improve the efficiency and extend the cycle life of the battery pack.Found by discharge characteristics test of gel maintenance-free lead-acid battery, there is a good linear relationship between the state of charge and terminal voltage of the battery pack, and according to this the subject putted forward a SOC estimation method based on open-circuit voltage method and current-time integral method. The method costs a small amount computing and low performance requirement for SCM, which is conducive to practical application in electric vehicles.Contra posing lithium iron phosphate battery and colloidal maintenance-free lead-acid battery, the subject respectively developed a battery management system, achieving state parameters monitoring of the battery pack voltage, charge and discharge current, single cell voltage, temperature, data analysis and storage. With RS-485and CAN bus communication functions, the system can achieve data communication with the motor controller or vehicle controller. The system can control the main circuit of the battery pack and battery pack thermal management. Having a friendly interactive interface, the user or maintenance personnel can view battery status data and set the parameters.