Design Of Battery State Monitoring System For Electric Vehicles

In recent years, with the advent of environmental pollution, mankind put forward to higher request in our living ervironment, Automotive emission which has been attracting increasing attention has become the primary problem. On the one hand, it is necessary to put in a lot of human and material resources to continue the research of fuel-saving and emission technology for further perfection. On the other hand, more and more people attend to the green power, hybrid electric systems at a different level and Plug-in electric system.For the popularization of electric vehicle (EV), substitution of conventional engine, it mostly ties in whether a high performance-price ratio, high-reliability and large capacity storage battery can come out. The development and application of large capacity storage battery depend on the high-accuracy and high-intensity monitoring system. Therefore, how to detect and monitor the storage battery working state of EV accurately becomes one of difficulties in the realm of battery technology. The power battery applied to EV is usually composed of several series-connected cells or parallel cells. Generally, the numbers of series-connected cells can reach to several tens. The battery monitoring system the paper presents takes two series-connected cells as an example. Of course, it is also suitable for the storage battery composed of more series-connected cells or parallel cells.The accurate acquisition of the State of Charge (SOC) is difficult in the working state parameters, because there is a non-linear relationship between the SOC and other parameters like ambient temperature, aging factors, discharge rate, charge-discharge efficiency and so on, especially for electric vehicle.The research on the monitoring system this paper presents is to complete the communication between the slave node and PC computer by means of CAN-BUS and MAX232 serial port. In addition, the software design utilizes self-carried communication class library of MATLAB to communicate with master node, and the acquisition and process of the datas from hypogyny computer are completed by epigenous computer. Meanwhile, friendly man-machine interface is designed by Graphical User Interface (GUI) of MATLAB to display the process results.The main modules of system include:battery parameters measuring module, CAN-bus communication module, Serial communication between master node and PC module, PC data acquisition and process module. In this paper, by means of analysis and research on the design scheme of the battery state monitoring system, the circuit of battery state parameter acquisition,the circuit of CAN-BUS and MAX232 serial communication, together with their compiled program, the compiled program about serial data acquisition and GUI indication by MATLAB7.0, the design of the detection scheme about battery SOC and the compiled program of Adaptive neuro fuzzy inference system (ANFIS) by MATLAB has been designed and completed, thus realized the real-time display of the battery working state parameters.