Research And Implementation Of Equilibrium Strategy For Lithium Battery Group Based On Cell To Group

At present,due to technical limitations,high power and high capacity lithium batteries can not be produced in large quantities.The most common use is technology mature,low voltage and small capacity lithium battery monomer.Therefore,in order to meet the voltage requirements of dozens or hundreds of volts,multiple lithium battery units need to be connected in series.Such a large series battery pack makes the structure of the battery pack complex.Because the battery itself has a problem of inconsistency,the overall performance of the battery pack becomes worse,the effect is not a simple proportional amplification of single cell performance degradation.With the increase of monomer number,the life and available capacity of battery pack will decrease exponentially.The difference in the performance of each monomer in the battery group will lead to the overcharge or over-discharge of some cell monomers during the continuous recycling process,which will seriously cause the risk of battery explosion.Th e reasons for the inconsistency between battery monomers are complex and various.The production process and operation process may lead to the disagreement between battery monomers.In this paper,the principle analysis of the inconsistency of lithium bat tery in the process of production and operation is carried out,and the influence of the unbalance on the battery group is also described.By comparing the advantages and disadvantages of different equilibrium criteria,the equilibrium method based on open circuit voltage is determined.Considering the practicality,a simple Rint circuit model is used to analyze the relationship between the parameters of the battery.Then,the expression of open circuit voltage under the conditions of different temperature and charge discharge ratio was obtained by experiment,and the equilibrium strategy of open circuit voltage under different working conditions was determined.This project applies LTC3300 equalizer combined with fly-back transformer to realize the active equilibrium of single to group,and deal with the imbalance of aviation lithium battery in operation.The function of the hardware and software of the balanced system is designed,the upper computer realizes the display of battery parameters and data storag e,The lower machine realizes the collection of parameters such as voltage,temperature,current and balanced operation.Finally,by comparing and analyzing the equilibrium time and equilibrium precision of the two equilibrium strategies under the same conditions,the feasibility of the equilibrium method proposed in this project is verified.It provides theory and data support for fast and accurate equalization of battery pack.