The Natural Cycle Life Test And Model Of Lithium Battery For Electric Bicycle

With traditional energy resources declining and the increasing awareness for theenvironment protection, the development of pure electric vehicles is becoming one of themost important energy conservation and emissions reduction measures around the world.Lithium-ion batteries have high power density as well as long cycle life, thus becoming oneof the main energy unit storages of new energy vehicles. However, because lithium-ionbatteries are chemically active and sensitive to temperature variation, the monitoring of thebattery conditions while practically driving is essential for its safe, reliable and efficientfunctioning under complex driving conditions. So the data of lithium-ion batteries underworking conditions needs to be collected and analyzed to determine the natural life cycleand the characteristics of lithium batteries. The specific research work of this study consistsof:(1) Using an electric bicycle as the carrier, an experiment platform was constructed,which includes battery management system aimed at measuring and recording experimentaldata. An comprehensive experimental method of testing lithium-ion batteries was proposed,which includes temperature, voltage and current of every single lithium-ion battery.(2) Lithium-ion battery life decline is analyzed qualitatively and quantitatively basedon measured data. The factors affecting battery’s life cycle and their relationships are alsosummarized. SOC and SOH’s influence on battery’s internal resistance are also analyzed,which helps to conclude that battery’s internal resistance is positively correlated to SOC’svariation, and negatively correlated to SOH’s variation.(3) Based on the research of existing battery model, one proper model was selectedand improved to suit this experiment. Input the experimental data to the model and getoutput data so they can be analyzed and compared. The average deviation of the data iswithin6%.(4) The inconsistency of every single battery is summarized, and its discrete degree iscalculated. SOH is introduced as the parameter of the variation of discrete degree. Therelationship between SOH and the variation of inconsistency of the battery is analyzed,arriving at the conclusion that the inconsistency of the battery becomes larger as SOHdecreasing.