Research And Implementation Of The Battery Management System

Electric vehicles is one of the new energy vehicles,the battery is the only power source.Power battery performance determines the cruising mileage and safety of electric vehicles.BMS(Battery Management System)is a key technology that ensures the high-performance output of the power battery.Mainly studying from two aspects of balanced circuit design and SOC estimation method to realize the protected balanced power battery pack and the battery SOC(state of charge)estimation.The difficulty of balancing control is to balance the indicators,such as high aging,excellent energy efficiency performance,low cost,simple circuit structure,high SOC estimation accuracy,to reasonably design balancing variable,real-time data sampling strategy,charging and discharging strategies and energy balance strategy.Designed a kind of balanced circuit based on pure switching matrix,the scheme is a type of non-dissipative battery balancing system,which is the lowest cost and the most easy to implement.It can control the on-off of any one single or multiple cell at any time,and even can control the on-off of the whole circuit.The balancing system improves the inconsistency in the cells effectively,to avoid the overcurrent,overheating,overvoltage,undervoltage and other damage to the battery.The difficulty of SOC estimation lies in the large amount of data to be collected,high precision.And the working process of the battery is a complex electrochemical change,the capacity of battery is affected by many uncertainties parameters that battery temperature,charging and discharging conditions,self discharge rate,etc.nonlinear battery status change has seriously hampered the prediction accuracy of the SOC.Therefore,how to make an accurate estimation of SOC according to the measurable battery parameters is a challenge.Proposed a SOC estimation method which combined with Ah integral method and OCV(Open Circuit Voltage)method,The combination of the two can complement each other,make up their own weaknesses,exploit their respective advantages to the full,and the circuit is easy to be implemented and controlled.On the problems of inconsistency between the series battery monomer in charging and discharging process,the paper designed a kind of balanced circuit based on pure switching matrix with only a MOS transistor.Taking monomer battery voltage as balancing variable,using voltage difference method.K10 Microcontroller real-time monitoring the battery information by acquisition module,it can control the on-off of switching MOS transistors,and then control the charging and discharging time of the monomer battery,to achieve a balanced charge and discharge.The design solved the inconsistency problems in series battery monomer.According to the current conventional SOC estimation method and its range of application,Measuring SOC initial value by the Open Circuit Voltage method,combined with Ah integral method,converting SOC initial value and the current sampling values into digital signals by an analog-to-digital converter(ADC),finally,inputing the digital signals into FPGA for data processing,so the SOC value can be obtained.Build a simple battery management system platform for experimental verification,the battery management system achieved effective management for the charging and discharging of lithium-ion battery pack,accurately estimate the SOC value,and reach the design targets.