Research On Power Li-on Battery Management System

With the world’s energy exhaustion and atmospheric pollution is aggravating,the electric vehicles has come to the attention of experts and scholars from all over the world for its less energy consumption and pollution-free advantages. And now most of them focus on battery management system, the vehicle control system, motor drive system on the three key core technologies. Whether the power battery management technology is mature or not which directly determines the pros and cons of the electric car vehicle performance. When the electric vehicle works, the battery is often accompanied by large current charge and discharge without rules, its work condition is extremely bad, if we want to exert the performance of the battery efficiently and durably, we must manage it and control it.This paper studies the key technology of battery management system on the basis of predecessors’ research results, and put forward some improvement methods with the deficiencies of previous. Firstly, the paper put forward a compound model of equilibrium solution, which improve the original scheme by combining the ferrying capacitance method with the bypass shunt resistance method, when considering the control signals of the ferrying capacitance method are susceptible by electromagnetic interference caused by current in the process of charging and discharging. The bypass shunt resistance method is adopted in the process of charging, which can reduce the rising near cut-off voltage of battery charging speed, and ensure all monomer battery charging can be filled. The solution take open equalization circuit for imbalance of the discharge process, when parking, balance on the basis of ferrying capacitance method. This scheme can not only avoid the wrong operation of equilibrium control circuit in the process of charging and discharging effectively, but also take balance the battery pack inconsistencies caused by charging and discharging process. Then the paper verify the effectiveness of equilibrium solution in the simulation analysis. Secondly, the paper use the traditional thought which combines the ampere-hour integral method and the open circuit voltage method, but amend the battery pack SOC estimation method combined with the equilibrium method proposed in this paper. The method take battery level changed caused by balance as influence factors, when the battery SOC value estimate in the process of the charge and discharged respectively. Then analyze the estimate process in the form of the simulation. Finally, the paper designs a whole architecture of battery management system in a main control board and multiple secondary control board. And make MC9S12DT128 and MC9S12D64 in Freescale 12 series as MCU of battery management system. The paper studies the status information acquisition method, temperature control, insulation protection, communication, and other functions in the battery management system, and designs them in the aspect of hardware and software.