Research On Power Battery Thermal Management System

Electric vehicles have achieved rapid development in recent years due to the high efficiency,energy saving and pollution-free characteristics.However,electric vehicles are difficult to start at low temperature,and problems related to power batteries such as spontaneous combustion or collision fires at high temperatures are gradually exposed.The main problem is the thermal runaway of the power battery pack,so thermal management of the power battery pack is extremely important.This paper takes 72Ah lithium iron phosphate battery(LiFePO4)and 100Ah ternary lithium battery as the research objects,proposes specific battery thermal management structure and implementation scheme for thermal management in low and high temperature environment.Using Fluent for numerical simulation and analyze the feasibility of the plan from the perspective of heat transfer and fluid dynamics,and the effectiveness of this system had been verified through experiments.Discharge experiments at 1C,1.5C and 2C rates under ambient temperatures of-20? to 40?,and charge experiments at 1C and 0.5C respectively.Obtained the relationship between temperature rise of the battery surface and the change of the open circuit voltage of the battery with time,under different ambient temperatures.Using the pulse charge and discharge test(HPPC)to determine the internal resistance of the power battery.and obtaining the heat production power of the single battery.Provide data support for analyzing the heat transfer law between batteries.Establish a battery thermal management model based on indirect heat transfer of copper rods and heat pipes,conduct low-temperature thermal management experiments based on copper rods and heat pipes and high-temperature thermal management experiments based on copper rods,study the best thermal management methods in different temperature ranges.The best thermal management effects that can be achieved under different thermal management methods.Using numerical simulation method to simulate the heat production of single battery and the temperature distribution of power battery pack under thermal management schemes.For the ternary lithium power battery,based on the thermoelectric cooling effect,the aluminum plate and heat pipe are used to conduct the heat dissipation management experiment of the battery pack under ambient temperature of 30?.Through numerical simulation and experimental verification,it can be concluded that the thermal management system can reduce the surface temperature of the battery by 5? without consuming external energy,and can control the surface temperature of the battery below 45? in the rate of 3C discharge.It shows that the correct calculation of the thermal management model and the rationality of the model,meeting the requirements of the power battery thermal management system.