Research Based On The Temperature Management System Of Pure Electric Vehicle Power Battery

Power battery temperature management is a core key technology for the stability and safety of pure electric vehicles.When range,charge and discharge speed and power are increased,higher requirements are placed on the high energy density,light weight and high output power of power batteries.This paper mainly takes the 18650 lithium battery as the research object,takes the temperature management as the starting point,and focuses on the heat generation mechanism and temperature transfer characteristics of the power battery from the three different dimensions of a single battery,a battery module and a temperature management system.The main research elements of this paper are.Firstly,this paper establishes a one-dimensional simplified thermal conductivity model based on the heat transfer of a single battery module,which theoretically accurately reflects the real state of a single battery,and proposes a two-dimensional model to achieve an exhaustive analysis of the change law of the central temperature of a single battery through the initial conditions,thermal boundary conditions and the thermophysical parameters of the battery.As time increases,the influence of the initial conditions on the central temperature of the power cell increases from initially dominant to gradually negligible,while in contrast,the influence of the thermal boundary conditions on the internal temperature of the individual cell increases from negligible to gradually dominant.Deviations in power cell temperature prediction mainly arise from the inaccurate assumption of initial thermal distribution uniformity,mainly in the first two stages,and the accuracy of the cell building model in the first and second stages is directly related to the assumption of initial temperature non-uniformity.Secondly,a power battery module heat transfer characteristics model is proposed to reduce the influence on cooling efficiency when heat and mechanical energy are transformed into each other by means of heat transfer distribution and cell distribution methods,and to obtain a battery module thermal temperature distribution with better heat transfer efficiency from theory.At the same time,the characteristics of the heat transfer of the battery module at cone angles of0°,60° and 90° are studied and compared using the method of establishing mathematical physical models.The influence of the cell spatial distribution density on the heat transfer of the cell module is also investigated.Then,the temperature management system of the power battery module of pure electric vehicles is constructed and the experimental method is improved.Based on the study of the internal heat transfer characteristics of the battery,the experimental test system is designed and built to test the composition structure of the battery module and the heat generation mechanism of the power battery,the specific methodological steps of the measurement experiment,the data processing of the measurement results and the non-ideal factors in the measurement process are analysed in detail and specific processing methods are given.Finally,the performance and improvement of the battery module temperature management system is studied.By analysing the heat transfer characteristics of the power battery module,the focus is on optimising the distribution of the liquid cooling module and improving the heat transfer of the battery module.Test experiments are conducted on three types of power battery modules with taper angles of 0°,60° and 90° respectively.Analysis of the experimental results shows that the closer the battery is to the coolant inlet,the earlier it enters the steady state,while the one with a taper angle other than 0° enters the steady state faster than the one with a taper angle of 0°.When the taper angle is 0°,there will be a "buffer zone" in the middle of the battery,so that the cooling capacity of the battery near the coolant outlet decreases.When the density is kept constant,the temperature dynamic range is lower than at 0° and 90° when the cone angle is 60°,but the overall performance of the temperature difference is instead the largest.