The Research Of Lithium Iron Phosphate Battery Management System

With the energy and environmental issues become increasingly prominent, electric vehicle (EV) with the merits of zero-emission and low noise is attracting more and more attention from governments around the world. However, there are still a lot of problems to be solved in the development of EV. Power battery and its management system as one of the core technology, is the crux of the industrialization and practicality of EV. This thesis, under the basic research on battery model and algorithm SOC, with the support of an EV project from a company named FA, aims to design a Lithium Iron Phosphate (LiFePO4) Battery Management System (BMS) and describes the Implementation.The thesis analyzes the current various power batteries in many performance indexes and indicates that the LiFePO4 battery is found to be a quite ideal power source for EV. Considering the role and function of BMS, the thesis discusses several key technologies and difficulties in the BMS and proposes focus of this research.According to the working principle and characteristics, the thesis analyzes many major factors affecting LiFePO4 power battery. Electrochemical model is selected for LiFePO4 power battery by analyzing some common models of battery, the thesis also put forward the theoretical deducing process and Simulation results for the model.In the estimation of SOC, some strategies of SOC estimating are displayed and analyzed. Then a comprehensive scheme of SOC measuring method has been raised, which is the combination of extended Kalman filter (EKF) and open circuit voltage. The method based on EKF is researched. Simulations and experiments are given at the same time.According to the actual requirement of power battery pack of FA's electric vehicle, a distributed BMS solution has been raised. The BMS is divided into two parts: one which is the underlying control module, based on PIC16f726 microcontroller, is designed to monitor the voltage, temperature and other information of the every battery; the other which is the central management module design, based on PIC32MX460F512L, is designed to measure the current and total voltage of the battery pack, implement SOC estimation, fault alarm and communication function. The two parts are communicated via wireless RF network. The thesis also makes a research on the design idea of function modular and software, and system is further verified the reliability and practicality through the experiments.