Prediction On SOC Of LiFePO₄Battery DSP-based

China will go beyond the United States which is the existing first country inauto production and consumption to become the world’s largest one about2020.At the same time, our country is confronted with the great challenge of energysaving and emission reduction. The pressure of environmental pollution compelspeople to abandon the traditional traffic tools, therefore, developed energy-savingand environmental protection have become an inevitable trend of electric vehic le.In the electric car batteries, with the traditional lithium-ion battery in the securityshortcomings, LiFePO₄batteries（lithium iron phosphate battery） is born tomeet people on the safety of batteries with high demand. Lithium iron phosphatein environmental protection, cycle life, material source and so on, it also hassignificant advantages. Because its chemical structure are stable which produceno free oxygen in overcharge cases, it is currently considered the best and mostsecure high current output power battery.Because the electric vehic le condition is complex, and if the batteryperformance data for the master is insufficient, the car with lithium ironphosphate battery modeling is not suitable, and it will result in a variety ofequilibrium problem to affect its service life in the process of using. Therefore,based on a series of battery performance testing, creat the first order RC andsecond order RC battery equivalent circuit model, introduce them respectivelyand make the cell model parameters identification.In order to estimate the battery state of charge（SOC） In a complexenvironment, the extended Kalman filter method is more severe in the currentvolatile environment by comparing a variety of estimation methods. ExtendedKalman filter can not only supply the current estimation, and also give the errorof the estimation. Therefore, in the establishment of the first Order RC andsecond order RC model, make use of the extended Kalman filter algorithm toestimate the SOC.The purpose of this study is to estimate the battery SOC hardware systembased on DSP, so the hardware design is the main part of the article description.Hardware system can be summarized into three parts: data acquis ition module,processing module and display module. Acquisition modules use themicrocontroller as the acquisition and control center for easy modular and follow-up applications. MAX17830is used as voltage and temperatureacquisition interface devices, and use the ACS712Hall current sensor as thecurrent collection equipment. For processing module, use TI’s DSPTMS320VC5509A development board as the master chip. Excellent processingspeed of the DSP and the suffic ient interface module for the system achieve agreat convenience. For display module, send the data to the host computer usingthe serial port.Based on the design of hardware systems, software design is essential. Thisarticle describes the software design based on the SOC estimation system,including a range of model parameter fitting process, the SOC estimationalgorithm processes, the interface communication module program design andhost computer communication program design. Finally, the article puts theestimated results of Extended Kalman filter algorithm compared with the Ahmethod’s. Through the serial experiments, the final results have verified thevalidity of the algorithm and error analysis.