Research On Adaptive Current Charging Strategy For Electric Vehicle Lithium Battery Based On Real-Time Internal Resistance Test

With the rapid development of electric vehicles,improving the charging efficiency of electric vehicles has attracted widespread attention from scholars.However,most of the traditional methods do not consider the charging loss of the battery,and the charging efficiency may not be high.Because the ohmic loss of the battery during charging is proportional to the battery’s internal resistance and the square of the current amplitude,and the internal resistance changes with the state of charge(SOC),use a charging current amplitude that is inversely proportional to the battery’s internal resistance Helps reduce battery charge loss.Therefore,based on the real-time detection of battery internal resistance,this paper proposes an adaptive current charging strategy.Compared with the conventional charging method,the charging method proposed in this paper can effectively reduce the charging loss and improve the charging efficiency of the battery.The specific research content is as follows:First,the background of lithium battery charging research is analyzed in detail,including the working principle,internal resistance structure and equivalent model of lithium battery.Based on this,the charging loss of lithium battery is derived,and the internal resistance test of lithium battery is also explained.Principle,select a suitable internal resistance test method as the test method of the lithium battery on-line internal resistance test system.According to the working principle of the EIS measurement method,the overall scheme of the internal resistance on-line test system for lithium batteries is designed.The working principle of the DC / DC converter in the real-time internal resistance detection system is analyzed,the large-signal and small-signal models of the DC / DC converter are established,and the stability analysis is performed.The real-time implementation of the internal resistance detection system is also analyzed,and the real-time detection of internal resistance by the online FFT is described in detail.An adaptive current charging strategy for lithium batteries based on real-time internal resistance detection is proposed.The proposed strategy includes applying a variable amplitude charging current based on the battery resistance,which causes the current to change with the state of charge and the charging rate of the battery.Firstly,the battery charge loss is theoretically analyzed,and then the implementation difficulties are analyzed.The method is theoretically evaluated for the effect of reducing losses,and then the proposed charging profile is defined for its implementation,and a solution using a stochastic method is proposed.An algebraic evolutionary algorithm to obtain the optimal charging curve.At the same time,the optimization of the number of discrete SOC intervals(N)is also discussed to find a compromise between the amount of calculation and the reduction of losses.An experimental platform was set up to verify the main research contents of this paper.A comparison experiment between the adaptive current charging strategy and the constant current charging strategy was carried out through a physical platform,and the experimental results were analyzed and demonstrated.The experiments show that this kind of adaptive current charging strategy based on real-time internal resistance test has an effect on reducing charging losses.Remarkably,the feasibility and superiority of the battery charging efficiency are verified.