Multi-Objective Constrained Optimal Charge Management For Lithium-Titanate Batteries

Recently,electric vehicles have become the new generation of clear vehicles because of the environment and energy problem are becoming more and more severe.As the power supplying unit of electric vehicles,battery system is the main factor which determines the performance of an electric vehicle.Compared with the traditional batteries such as lead acid batteries and nickel metal hydride batteries,lithium ion batteries have been popularly used in electric vehicles,owing to their high energy density,long cycle life and high reliability.Although the market of electric vehicles is becoming larger and larger,their endurance mileage,charging speed,service life and safety are still nonnegligible factors.These factors are more severe in the public transit of developed cities like Beijing and Shanghai,because firstly,public transit has little tolerance on potential safety hazards.Moreover,there are no fixed parking lots for buses because of the shortage of land in developed cities.However,these cities usually have more demands on public transit.Thus,electric buses have to adapt the method of fast charging in the daytime.Then,the LTO batteries become the first choice in such applications.Proper optimal charge management for LTO batteries can guarantee the batteries are fully charged with shortest time,and at the same time,deduce the charging cost greatly.This paper developed a terminal-voltage-prediction model for LTO batteries based on the Thevenin model.And the nonlinear effects of battery state of charge and charging current on model parameters are analyzed based on the experimental data.Then,we further developed the multi-objective constrained optimal charge management based on the battery model.Finally,a practical example is given to investigate the feasibility of our method.