Design Of Electric Vehicle Battery Management

With the rapid development of the economy, the problem of environmental pollution and energy consumption issues become more prominent, in the face of the pressure of these two aspects, energy saving and environmentally friendly nature of electric vehicles has been hampered by the attention, the research and development of electric vehicles has been included in the "Eighth Five-Year Plan" and "the Ninth Five-Year Plan "period as a major scientific and technological projects by China. Lithium battery has been becoming the energy source of the electric car because it is more environmentally friendly, high specific energy.Lithium battery management system is an important part of the whole system of electric cars, it is the connection part of electric drive systems, energy systems, and auxiliary systems to ensure coordination between the various systems control, to achieve the the normal operation of electric car. Lithium iron phosphate battery management system for voltage characteristics, management and control of lithium iron phosphate charge and discharge characteristics of lithium iron phosphate group, effective to achieve optimal control.According to main charge regulator topology of drive lithium battery management system, this thesis introduce the evolution of the main charge regulator topology, effectively reduce the order of the system, and improve the stability of the whole system. The driving part of the main switch tube charge regulator system, using a novel pulse transformer isolation driven, floating drive output voltage, increase the reliability of the system, suppress the transient spike to protect the MOSFET switch tube.The performance of lithium iron phosphate is stable, but over-charge,over-discharge and other harsh states, cause the decomposition of the internal electrolyte, result in the deterioration of the characteristics of lithium iron phosphate, even explode to threaten the personal safety of users. Thus, it is necessary to install the protection circuit in a lithium battery pack. Lithium battery protection circuit would include at least overcharge protection, over-discharge protection and short circuit protection three, the purpose is to prevent the battery charging and discharging process caused by lithium battery group overvoltage, overcurrent short-circuit damage phenomenon.Lithium battery pack is how shares of lithium iron phosphate composition per cell characteristics differences for a long time the battery energy is not patched, causing damage to the entire battery pack, so the introduction of a single strand of battery voltage, current detection and energy balancing system.The current sampling of the power of the battery pack use a precision Hall element.A slight voltage variation of the input voltage output by the Hall sensor device, the proper response to a change in current trends. This technique,higher accuracy,the use of fewer components, lighter in weight, avoid the energy loss of the sampling resistor. In order to show better tracking of the sampling circuit characteristics, we carried out sampling circuit feasibility, theoretical analysis and simulation waveform records qualitativly.In the end of the paper, given the trends of the development direction of the battery and battery management system. summarized and prospected the design, a large-capacity battery method to reduce the degree of complexity of the lithium battery management system.