摘要

电动汽车高速发展的今天，动力电池系统作为其发展的关键和瓶颈，技术研发上也不断地取得突破。正是因为动力电池的重要地位，其结构设计上关系到整体系统的各项性能特点和安全要求，进而影响到整车的综合表现。本文根据课题组内对设计车辆的整车要求以及对动力电池的参数要求，完成电动汽车动力电池包的结构设计和相应的特性分析工作。

首先，本文分析动力电池包设计过程中必须满足的各项安全性要求，确定采用3750个NCR18650型锂离子电池单体，通过50并75串的结构形式构成动力电池包的基本框架。电池包系统整体电池容量达到设计要求的36.5kW·h，电池总电压为270V，验算其满足理论上最大续航里程达到240km。动力电池包内部结构为5个相同规格的电池模组箱体呈异形T字排布，采用液体散热的冷却方式，防水防尘密闭等级为IP67级，安装于汽车底盘下方，车架纵梁跨度之间。所设计得电池包的总质量预估为364.382kg，计算得功率密度达到555.74 W/kg，基本满足设计要求的包级功率密度目标要求。

其次，完成对所设计的动力电池包进行结构特性分析和校验。运用CATIA三维建模软件完成动力电池从单体级到模组级再到整体包级的实体建模，结合ANSYS有限元分析软件分析验证颠簸＋紧急制动、颠簸＋紧急转弯两种典型组合工况下动力电池包的结构强度，在ANSYS Workbench平台进行电池包的自由模态强度分析。阐述当前电动汽车在碰撞性能上的要求，碰撞测试的必要性；结合安装位置和结构设计特点，分析了电池包各个方面的防碰撞措施，并模拟纯电动汽车侧面碰撞情景，运用LS-DYNA求解器和LS-PrePost软件对电池包进行模拟侧面碰撞分析。

最后，介绍未来动力电池随着性能的下降，使用寿命到达上限，将会有大量的电池退役报废，当前动力电池循环回收利用上前景广阔；分析目前热点研究话题——“快速换电”的突出优势和面临的难题；结合上述现象重点分析了所设计的电池包可重组可重构性。

关键词：电动汽车；动力电池；结构设计；强度校验；碰撞性能；单体重构

Abstract

With the rapid development of pure electric vehicles, power battery system is the key of its development, and breakthroughs have been made in technology research and development. Because of the important position of power battery, its structure design is related to the performance characteristics and safety requirements of the whole system, and then affects the comprehensive performance of the vehicle. In this paper, according to the requirements of vehicle design and parameters of power battery, the structure design and corresponding characteristics analysis of power battery pack for pure electric vehicle are completed.

Firstly, this paper analyses the safety requirements that must be met in the design process of power battery pack, and determines that 3750 NCR 18650 lithium-ion battery monomers are used to form the basic framework of power battery pack through 50 and 75 series structure. The overall battery capacity of the battery pack system meets the design requirement of 36.5kW· h, and the total battery voltage is 270V. The theoretical maximum endurance range of the battery pack system is 240 km. The internal structure of the power battery pack is five battery module boxes of the same specifications arranged in a special T-shaped arrangement. The cooling method of liquid heat dissipation is adopted. The waterproof and dust-proof sealing grade is IP67. The power battery pack is installed under the chassis of the automobile, and the span of the longitudinal beam of the frame is between. Basically meet the design objectives. The total mass of the designed battery pack is estimated to be 364.382 kg, and the calculated power density reaches 555.74 W/kg, which basically meets the design requirements of the package level power density target.

Secondly, the structural characteristics of the power battery pack are analyzed and verified. CATIA three-dimensional modeling software is used to complete the solid modeling of power battery from single level to module level and then to whole package level. The structural strength of power battery pack under two typical combined working conditions of bump+emergency braking and bump+emergency turning is verified by ANSYS finite element analysis software. The free mode strength analysis of power battery pack is carried out on ANSYS Workbench platform. The requirement of collision performance and the necessity of collision test for electric vehicle are expounded. Combining with installation position and structural design characteristics, anti-collision measures in all aspects of battery pack are analyzed, and side collision scenario of pure electric vehicle is simulated. LS-DYNA solver and LS-PrePost software are used to simulate side collision analysis of battery pack.

Finally, with the performance degradation and service life reaching the upper limit, a large number of power batteries will be decommissioned and discarded in the future, and there will be broad prospects for recycling and utilization of power batteries at present. The outstanding advantages and difficulties of the current hot research topic - "rapid power change" are analyzed, and the reconfigurability of the designed battery pack is emphatically analyzed combined with the above phenomena.

Key Words：pure electric vehicle; power battery; structural design; strength check; collision performance; single body reconstruction.