Dynamic Response Analysis Of EV's Battery Pack On Collision Condition And Its Safety Evaluation

Promoting the use of new energy vehicles,especially electric vehicles,is an effective measure to cope with global energy shortage and environmental pollution.The problem of electrical vehicles safety is increasingly prominent because of the excessive pursuit of development speed.The repeatedly explosion of electrical vehicles makes people has doubts on its development and application,and restricts its promotion and development severely.Therefore,the problem of security has become a technical problem to be solved.As the power source of the electric vehicle,power battery is the core component of electric vehicles,and its security problem,especially the collision safety is the key of the electric car safety.However,most of the researches on the collision safety of battery pack emphasize on the battery box and its installation location instead of its internal security.In order to solve this problem,this paper put forward a safety performance analysis and evaluation method for the battery box and the internal structure in the process of collision,combining with the development of a battery pack.First of all,experimental study on the mechanical properties of cells and the voltage and temperature characteristics of the cells in the indentation tests with hemispherical punch was carried out.Based on the experimental results,A homogenous model of a single cell was developed and calibrated.A failure criteria was built by the means of converting the failure of lithium-ion battery to the mechanical failure.Then,with the premise of analyzing the characteristic of battery pack,a refined model of battery pack,which takes into consideration the cell,the cell contact,the fixed structure and the inner shelf,was proposed.This model was used for simulating the dynamical behaviors of battery pack on the side rigid column collision and the front 100% rigid wall collision,the collision results of battery pack and its internal structure in the aspects of deformation and acceleration was analyzed and evaluated.At last,This paper presents a method for evaluating the safety performance of electric vehicle battery pack,based on the theory of analytic hierarchy process and fuzzy comprehensive evaluation method.The research results show that the homogenized model can capture mechanical response of cell,and that the mechanical failure occurs when the maximum tensile stress of the jellyroll reaches 18 MPa.The maximum tensile stress of the jellyroll in both collision conditions is less than the failure limit;however,due to the impact of the battery module in the process of collision,the inner frame of the battery pack and the related electrical components deformed seriously,which leads to a short circuit risk.Meanwhile,the comprehensive evaluation results indicates that the integrated performance of battery pack is poor,and there is a serious security risk.