The Development Research Of Battery Management System Based On The PLC On The Small Pure Electric Coach Vehicle

Electric vehicle, with the advantage of energy saving and environmental protection, hasattracted more and more attention, and is regarded as the development trend of antomobileindustry. The world’s major companies, universities and instituties have carried on thoroughresearch on this problem and have made some remarkable progress. However, the slowlydevelopment of power battery and its applications becomes the bottleneck of thepopularization of EV. The BMS, as the necessary technology of EV，directly detects andcontrols the process of EV’s battery operation, including the charging and discharging current,the battery voltage and temperature, consumption estimation, the balance between monomerbatteries and battery failure diagnosis, to improve lifetime and efficiency of the battery and toinsure the safety. It has important engineering significance for the industrialization of the EV.This paper develops a set of energy management system controlled by PLC based on theprojects of09-32k and CX1249-4. Firstly, The research significance of BMS is discussed anda lot of the technical stuation is researched, Combined with the existing conditions, theinformation acquisitting and state estimating scheme is put forward in the paper. Then, thehardware circuit which solves the six pieces of batteries’ accurate voltage, current,temperature collection works with “inspection technology” that lays a good foundation toaccurately judge the battery status, is designed and set up. At the same time, the softwareprogramming is designed. The parameters used in the program is obtained by the drivertraining EV with experiment. The “double SOC” strategy which use the actual capacity thatcan be released on the real vehicle as the initial capacity when calculate the SOC.SOC1onlyreflects the amount of charged or discharged electricity. SOC2is the revised charged stateunder the temperature, discharge current. Since then, the initial capacity updates automatically,mostly avoid the effect of aging and self-discharge on SOC’s estimation. It adopts the module,integration and simple design principle during the design. And anti-interference measures arefully considered to ensure the reliability of the system. Finally, do a lot of related indoorexperements and simple real vehicle tests to validate the software and hardware design.The acquisition value of temperature, voltage, current and charged state of the Indoor tests are consistent with expected results, shows that hardware design and softwareprogramming are correct. the battery initial capacity is obtained and the voltage, temperature,current signal, the state of charge value in the different time wil be recorded through the realvehicle test, the result shows that temperature, voltage, with large deviation that needs to beimproved, is affected by electromagnetic interference. SOC estimation within about tenpercent’s deviation, has certain practical value. Charging test firstly ascertains the chargingefficiency, improving the charging part of the program, so that the system can accuratelyreflect the state of charge when the battery is being charged.