Research Of Midium-scale Lithium-ion Battery Management System Based On AD7280A

Mankind is confronted with the dual pressures of energy crisis caused by the increasing depletion of traditional fossil fuels and environmental pollution caused by the burning of fossil fuels, which is urgent to develop new energy sources. Characterized by high terminal voltage, high energy density, high efficiency, long life, no pollution and so on, Lithium-ion batteries(lithium battery) is environmentally friendly battery with excellent performance as a kind of new energy storage medium. The development of lithium-ion battery management system(BMS) plays a key role in exerting its performance efficiently, ensuring its safety in operation and promoting its large-scale application.In recent years, with the development of electric vehicles, electric bicycles, and other application devices, enormous progress has been made in BMS. But both the internal characteristics of the lithium battery and external work environment are very complex, which needs high requirements and demands for the performance of BMS. Because of various reasons, the technology of BMS is still far away from being mature both domestic and overseas, which limits the spread of lithium batteries as the power energy. At present, BMS research mostly concentrate on such large-scale battery pack as electric vehicles, while the research relate to the medium-scaled BMS managing dozens of cells lags a lot.In recent years, BMS has been rapidly developed with the current development of electric vehicles, electric bicycles, and other application devices. While because of various reasons, the technology of BMS is still far away from being mature both domestic and overseas, which limits the spread of lithium batteries as the power energy.The medium-scale battery pack management system typically contains dozens string lithium-ion cells, which is mainly used for electric bicycles, backup power, solar lights and other energy storage devices. In this paper, the medium-scale battery management system includes the key technical SOC(state of charge) estimation and cell balancing. Combined with the practical application of embedded hardware system, the BMS mainly use the chips AD7280 A and STM32, achieving some applicable results. The research work is mainly reflected as follows:1. Considering the inaccuracy of power lithium-ion battery SOC estimation using conventional Ah algorithm, the improved Ah algorithm is presented and the SOC initial value is revised using the extension Kalman filter(EKF) based on Thevenin battery model, which increases the SOC estimation accuracy.2. With regard to the series battery pack equalization, passive equalization method is energy-consuming and active equalization method is difficult to implement with low security. Low-energy automatic equal method is proposed on the basis of traditional bypass balancing method, automatic to balance the battery and available to monitor the the voltage, current and temperature continuously, which reduces energy dissipation and greatly improves the security of the system with the cooperation of the hardware and software.3. This paper has designed the hardware experimental platform of battery management system for managing 12 series 18650 lithium-ion battery cells, realized the embedded system software, and accomplished the PC applications by using Labview language. The battery pack status is real-timely monitored and displayed on PC applications during the experiment.4. Experiments referred to charging, discharging and balancing the battery pack have been smoothly conducted with the application of the BMS designed in this paper. The research result shows that the battery management system can better manage the battery pack, meeting the needs of medium-scale lithium-ion battery pack management.