Research On Battery Management System For Extended-range Electric Car

With the continued deterioration of environment and the shortage of energyresources, electric vehicle (EV) has already become the thing which people paymore attention to. For its pollution free and energy saving, EV has become the futureof the automotive industry. As one of the key to the commercialization of theelectric vehicle, the development of the battery management system (BMS) isconsidered as one of the key techniques in electric vehicle. With the rapid progressin power density and energy density increase of the lithium-ion batteries over thepast decade, electric vehicles with lithium-ion battery packs as power sources havebeen intensively concerned. Due to the voltage and power requirements, the batterysystems are usually composed of up to hundreds of cells connected in series orparallel. The difference between cells would affect the performance of the batterypack.The characteristics of LiFePO4batteries are closely connected to ambienttemperature. The capacity characteristic, resistance characteristic, open circuitvoltage characteristic and polarization capacitance are important parameters toreflect the performance of batteries. Experiments are carried out to study the effecton the parameters of battery at different temperature.Considered the structure of extended-range electric car, a set of integrated BMSis designed, and Master-slave is accepted. This paper introduces detailed thehardware design of the slave part, includes the cell voltage acquisition, temperatureacquisition, CAN bus communication circuit and so on. Secondly the μC/OS-IIoperating system migration is introduced, and functional modules based onoperating system are designed, which include the SAE J1939protocol stack, thedata storage procedures. The final design is PC software based on LABVIEW.Test experimental methods are conducted built on the hardware and softwaredesign. The stability test is put into practice in the real vehicle running test andmeasurement accuracy and dynamic stability test are carried out at laboratory.Result show that the BMS has good stability and accuracy.