18650 Lithium Battery Heat Production Model And Application Research

In recent years,the electric vehicle industry is in a period of rapid development.As the power components of electric vehicles,the performance of batteries is a key factor that restricts the development of electric vehicles.Due to the excellent energy density of ternary lithium batteries,the market share of ternary lithium batteries has been increasing year by year,and it has completely occupied the mainstream position.At the same time,the safety problems caused by lithium ion battery heat abuse have gradually gained people's attention.Therefore,the study of the thermal characteristics of the ternary lithium-ion battery and the heat dissipation characteristics of the battery pack is critical to the design of the thermal management system.This article uses the NCR 18650 B ternary lithium-ion battery as a research object,and its main work as follows:(1)Disassemble the NCR 18650 B ternary lithium-ion battery to understand the internal structure of the battery,and divide the internal heat generated in the battery into ohmic heat and reaction heat,and analyze the influencing factors of ohmic heat and reaction heat,respectively,and determine the calculation method of each heat transfer physical property parameter of the battery.(2)A battery charge and discharge test stand was set up,in which the operating temperature of the battery was controlled using a thermostat box,and six K-type thermocouples were placed on the surface of the battery to obtain the surface temperature of the battery.The battery internal resistance test experiment,the battery electromotive force temperature influence coefficient experiment,the battery discharge temperature rise experiment and the battery charge and discharge performance experiment were performed.The experimental data were collated,and ohmic internal resistance and polarization internal resistance change law with temperature and SOC,the variation law of the electromotive force temperature influence coefficient with SOC,the law of temperature rise of the battery surface with different discharge rates under different ambient temperatures and the change law of charge and discharge capacity under ambient temperature were analyzed.(3)The internal structural parameters and material properties in the battery are obtained by measuring and consulting the literature and used to calculate the parameters of the heat transfer characteristics of the battery.The gas flow velocity in the incubator is obtained through experiments and used to determine the heat transfer boundary condition of the battery,and the high-precision battery production mode is established based on the experimental data.The thermal approximation model was used to conduct transient simulations of battery cells under different ambient temperatures and discharge rates.The internal temperature distribution of the battery was analyzed,and the temperature at the midpoint of the battery was compared with experimental test values.(4)Cooling transient simulation study was performed on a 12-cells battery pack,in which the battery was discharged at a constant current of 2C.The simulation study investigated the flow and radiate characteristics of series batteries at cell spacings of 2mm to 18 mm,the flow and radiate characteristics of the series cells from 3mm to 18 mm between the cell and the wall,and the flow and radiate characteristics of the 12 cells in parallel with various arrangements.An optimization scheme was proposed for the 3×4 layout structure to analyze its flow and radiate characteristics and compared with the original scheme.