Lithium Ion Power Generation Based On Echelon Research On Pool Management System

When some single batteries in the lithium-ion battery pack have problems or the battery pack can no longer make the electric vehicle reach the corresponding performance,it will be eliminated.However,most of the eliminated lithium-ion batteries can be reused.Re grouping and effective management of retired lithium battery can realize the echelon utilization of retired lithium battery,but some characteristics of retired lithium battery will be released and changed with echelon utilization,so it is not suitable to use the management system of new battery to manage it.Therefore,it is of great significance to study the characteristics and management methods of retired lithium batteries.The estimation of the health status of retired lithium batteries is greatly affected by noise,which is very important for the management of the echelon utilization of lithium batteries.In order to more accurately estimate the health status of retired lithium batteries,the ohmic internal resistance characteristics of some retired lithium batteries were studied.After determining the inevitable relationship between the ohmic internal resistance and the health status of retired lithium batteries,taking the ohmic internal resistance of retired lithium batteries as the research object,the health factors that can determine the aging degree of lithium batteries were constructed.Based on the data-driven method,the cubic spline interpolation method is selected as the algorithm to study and establish the relationship model between the health factors and the health state in the offline state,and the online estimation of the health state of the echelon lithium battery is realized by calculating the health factors online.In order to improve the efficiency of echelon utilization and slow down the life decay of retired lithium battery,this paper based on the flying capacitor method,increased the capacitance and field effect transistor,and developed an equalization circuit suitable for echelon utilization of lithium battery to balance the state of charge of retired lithium battery.Each cell has its own charge transfer capacitance.Under the cooperation of pulse wave,the cell in the battery pack can balance the adjacent or no adjacent cells by two common wires at the same time.Finally,a simulation model is established to verify the equalization effect.Then according to the functional requirements of the management system,the main functional circuits of the echelon lithium-ion battery management system are designed,including data acquisition circuit,safety protection circuit and communication circuit.Finally,the experiments of health state estimation and charge discharge equilibrium are carried out.The experiment of health state estimation shows that the error between the measured data and the estimated data is [-0.4%,0.2%],and the error is small,which verifies the feasibility of the estimation method.In the charge discharge equalization experiment,the battery parameters are set to verify the equalization effect of the equalization circuit.The results show that under the same conditions,compared with the traditional equalization circuit,the circuit improves the equalization speed and efficiency,reduces the equalization time by 22-61 s,and improves the equalization efficiency by 14%-31%.