With the rapid growth of the global electric vehicle industry, driven by increasing environmental awareness and strong policy support, the demand for reliable and safe power battery packs has become paramount. In China, the electric vehicle market, often referred to as China EV, is expanding quickly as manufacturers integrate intelligence and electrification. The battery pack, a core component of electric vehicles, is mounted on the vehicle frame and subjected to various extreme conditions during operation, such as acceleration shocks and repetitive loads. These can lead to safety risks due to insufficient strength, stiffness, or fatigue damage. Therefore, in-depth analysis and evaluation of the battery pack’s structural performance are essential to enhance its mechanical properties, extend its lifespan, and ensure safety and reliability. In this study, I employ finite element simulation theory to analyze the structural characteristics of a battery pack, providing theoretical guidance and technical support for modeling, simulation, and optimization in the context of electric vehicle development.
The finite element method (FEM) is a powerful numerical technique for solving engineering problems, and its application to battery pack analysis involves several key steps. First, structural discretization divides the mechanical structure into a finite number of elements connected by nodes, forming a discrete model that represents the original object. This process allows for the approximation of complex geometries, which is crucial for electric vehicle components like battery packs. Second, unit analysis includes selecting a displacement mode, where the displacement within an element is described as a function of coordinates. For instance, the displacement function can be expressed as: $$ y = \sum_{i=1}^{n} \alpha_i \phi_i $$ where $\alpha_i$ are undetermined coefficients and $\phi_i$ are functions related to coordinates. Next, the unit stiffness equation is established, representing the equilibrium equation for each node in the unit. This can be written as: $$ [k]^e \{\sigma\}^e = \{F\}^e $$ where $e$ denotes the unit number, $\{\sigma\}^e$ is the node displacement vector, $\{F\}^e$ is the node force vector, and $[k]^e$ is the unit stiffness matrix that reflects the stiffness characteristics. Additionally, equivalent node forces are calculated by transferring surface forces, concentrated forces, or volume forces to the nodes. Finally, overall analysis combines boundary conditions and equilibrium to form the global finite element equation: $$ [K] \{\sigma\} = \{F\} $$ where $[K]$ is the total stiffness matrix, $\{\sigma\}$ is the node displacement vector, and $\{F\}$ is the load vector. Solving this equation yields strain and stress distributions, which are vital for assessing the structural integrity of electric vehicle battery packs.
To build the finite element model of the battery pack, I followed a systematic workflow, as illustrated in the process below. This involves measuring structural parameters, simplifying the geometry, setting material properties, meshing, optimizing mesh quality, and applying boundary conditions. The battery pack’s geometric structure was modeled based on actual dimensions, focusing on the box, cover, and bracket components. For simplification, battery cells were equivalent to concentrated mass points connected to the box via bolts, and contact surfaces between components were treated with appropriate tension and friction factors. The key parameters and material properties are summarized in the following tables, which are essential for accurate simulation in the electric vehicle context.
| Parameter | Value |
|---|---|
| Length (mm) | 770 |
| Width (mm) | 560 |
| Height (mm) | 275 |
| Total Mass (kg) | 158 |
| Nominal Capacity (A·h) | 150 |
| Nominal Voltage (V) | 76.8 |
| Component | Material | Elastic Modulus (GPa) | Poisson’s Ratio | Density (kg/m³) | Shear Modulus (GPa) | Yield Strength (MPa) |
|---|---|---|---|---|---|---|
| Lifting Lug | Structural Steel | 201 | 0.30 | 7850 | 76 | 250 |
| Cover Plate | Structural Steel | 201 | 0.30 | 7850 | 76 | 250 |
| Box | Structural Steel | 201 | 0.30 | 7850 | 76 | 250 |
| Bracket | Structural Steel | 201 | 0.30 | 7850 | 76 | 250 |
| Strapping Band | Stainless Steel | 193 | 0.31 | 7750 | 73 | 210 |
In the static strength analysis, I applied a gravitational acceleration of 9.8 m/s² in the negative Z-direction and fixed constraints at the installation holes of the six lifting lugs. The results revealed that the maximum displacement occurred at the center of the battery pack cover, with a value of 2.6 mm, indicating insufficient stiffness that requires optimization. The stress distribution showed that the brackets near the air duct endured high stresses, with a maximum equivalent stress of 19.14 MPa. The plastic strain was zero, confirming that the battery pack remained in the elastic deformation state under self-weight, which is critical for the durability of electric vehicle systems.
For typical static工况 analysis, I considered five common driving scenarios that electric vehicles encounter, such as braking, acceleration, turning, and climbing. These conditions impose inertial forces on the battery pack, and their loading parameters are based on gravitational acceleration (g = 9.8 m/s²). The table below summarizes the acceleration components in the X (driving direction), Y (left perpendicular to driving), and Z (upward perpendicular to driving) directions for each scenario.
| Scenario | X (g) | Y (g) | Z (g) |
|---|---|---|---|
| Emergency Braking on Bumpy Road | +5 | — | -2 |
| Start Acceleration on Bumpy Road | -3 | — | -2 |
| Left Turn on Bumpy Road | — | +3 | -2 |
| Right Turn on Bumpy Road | — | -3 | -2 |
| Climbing on Bumpy Road | -1 | — | -2 |
Simulating these工况 provided deformation and stress cloud diagrams. For emergency braking, the maximum stress of 54.841 MPa was located at the connection between the left front lifting lug and the box, with a deformation of 0.653 mm at the cover center. In start acceleration, the stress peaked at 34.853 MPa at the left rear lug, and deformation was 0.655 mm. For left and right turns, stresses were lower (0.042 MPa and 0.045 MPa, respectively), with minimal deformations around 0.0007 mm and 0.0006 mm. During climbing, the maximum stress was 0.026 MPa at the cover-box connection, and deformation was 0.0006 mm. These results demonstrate that the battery pack possesses adequate strength and stiffness to withstand typical electric vehicle operating conditions, with maximum deformations within acceptable limits, ensuring safety for China EV applications.
In conclusion, based on finite element theory and geometric parameters, I optimized the battery pack model through proper meshing and boundary conditions. The static strength analysis and typical scenario simulations validated the structural feasibility and safety, with maximum equivalent stresses and yield strengths well below material limits. However, the cover plate’s stiffness requires enhancement to reduce deformation. This study offers valuable insights for further structural optimization of electric vehicle battery packs, supporting the advancement of China EV technology and contributing to the global shift toward sustainable transportation.