Design Of LiFePO₄Battery Experiment Platform With Large Capacity

With energy crisis and environmental issues becoming increasingly grievous, the electric vehicles those have advantages of a wide source of energy, low emission and low noise have received more and more attention. As the core of electric vehicles, the development and improvement of battery and BMS (Battery Management System) have become the focus of the automobile manufacturers and research institutes.This topic is based on the task named "Research on the Key Technology of Explosion-Proof Trackless Rubber Tyred Electric Vehicle Used in Mine" which is from Beijing Municipal Science and Technology Commission, and the main task is to complete the design of LiFePO4battery experiment platform with large capacity, and verify the function of the experiment platform.At first, this paper introduces the present status of research at home and abroad of electric vehicles, power battery and BMS. Then presents the details about the currently common methods of SOC (State-of-Charge) estimation including ampere-hour integration approach, open-circuit-voltage approach, internal impedance method, Neural Networks method, Kalman Filter method, the equivalent circuit model method. According to the features of target battery, this paper selects the mixture of open-circuit-voltage and ampere-hour integration approach to estimate SOC, which is a basis of obtaining the method of estimating SOC of battery pack. Building the experiment platform of battery pack is the major work of this paper which is important for the subsequent research of the performances of LiFePO4battery pack. The experiment platform includes a battery pack, main circuit, control circuit, manual detection terminal, BMS and PC monitoring interface. In addition, according to the experiment requirements, experimenter can choose appropriate load to do charging and discharging experiments on the battery pack. Battery pack consists of nine cell packs in series, and each cell pack consists of12cells in series. The main circuit and control circuit is used to turn on/off the battery pack-load circuit, measure and display the output voltage and total current of the battery pack and play the role of guardian of the battery pack and load terminals. Manual inspection terminal is applied to measure the cell voltages, the total voltage and other data online or offline with a multimeter in order to check the data measured by the BMS. BMS in this paper is comprised of one main board and nine slave boards, each slave board is responsible for measuring the voltages and temperatures on each cells in its own cell pack and calculating maximum and minimum voltages, maximum and minimum temperatures and their corresponding IDs, and sending the information to the main board. The main board is used to measure the important parameters such as total pack voltage, total current, SOC, and etc. And the main board also receives data to the PC monitoring.After completing all the work above, this paper uses ARBIN BT2000and ARBIN EVTS to do charging and discharging experiment on the monomer and pack, and verifies the function of the experiment platform by cell and pack experiments and at last analyses the experiment data.