Research On LiFePO₄Battery System Integration And Management System Of Electric Vehicle

The shortage of petroleum resource along with the increase of fuelpollution makes the electric vehicle （EV） draw more and more attentions.Battery control strategy and Battery Management System （BMS） is the keytechnology and also the most difficult part of industrialization of electricvehicles. The development of battery technology especially the physical&chemical character and thermodynamic behavior of the batteries nowadayscan hardly meet the shark EV demands including high energy density, highsafety performance, low cost and long life cycles. So it is necessary to notonly improve the manufacturing technology of batteries but also develop ahigh performance battery management system which can scan and collect allthe online information of battery system and precisely estimate its key statesand parameters and ensure the high voltage safety of the whole system.This paper, which is based on the national ‘973’ project, mainlyresearched on battery system integration and battery management system. Itincludes for major parts. First, data base construction for the furtherdevelopment of the battery system. Second, hardware design technologywhich includes battery state data sampling system design, equalization systemdesign and high voltage safety system design. Third, parameter estimation ofbattery system. Last but by no means the least, simulation and optimization of thermal management of battery system.The hardware system, which is one of the basic parts of batterymanagement system, includes several sampling units and one major controlunit which is called as dispersive pattern, can be easily applied on differenttype of electric vehicles.Parameter estimation system, which includes state of charge （SOC）estimation, state of health （SOH） estimation and maximal charge anddischarge power estimation, is the key part of software design of the batterymanagement system. A new algorithm and method is also applied on this partwhich can improve the accuracy of the parameter prediction.Thermal management system develop a precise thermal model based onthe principle of heat generation of LiFePO₄battery several cooling modeswere researched and compared and the parallel venation mode is selected tocool the battery pack. The battery finite element model was also established toanalyze the battery system heat distribution by simulation, the simulationresults are certified by the test.In the end, the vehicle battery management system has been successfullyapplied and verified in a real vehicle which will be exposed on Shanghai2010EXPO. The test results demonstrate that the new system is accurate andreliable and the design and research methods proposed in this paper are usefulin accelerating the development of vehicle onboard battery management.