In the context of the global energy transition and the “dual carbon” strategy, the large-scale integration of renewable energy sources such as solar and wind power has become a core pathway for optimizing the energy structure. However, the intermittent and fluctuating nature of renewables poses significant challenges to the stable operation of power systems, necessitating energy storage systems to achieve temporal and spatial energy transfer and dynamic regulation. Residential battery energy storage systems, as terminal devices for distributed energy storage and consumption in households, not only enhance home energy utilization efficiency but also establish emergency backup power systems, reducing dependence on the traditional power grid. Therefore, studying the structural reliability of residential battery energy storage systems is of great importance for household electricity usage. During transportation, vibration is the primary factor affecting the structural reliability of these systems. In light of this, this paper focuses on the structural design of residential battery energy storage systems, based on actual transportation environments, combining finite element simulation and experimental verification to ensure the rationality of the designed battery energy storage system structure. The aim is to provide high-safety solutions for residential energy storage products and promote the technological upgrading of user-side energy storage.
Finite Element Model of the Residential Battery Energy Storage System
Overall Structure of the Residential Battery Energy Storage System
Based on the structural and capacity requirements of the residential battery energy storage system, the system consists of a battery pack and a high-voltage box. The battery pack supports stacking of 2 to 5 battery modules, with a single module capacity typically no less than 5 kWh. Currently, the 50Ah cell solution performs best in the market; selecting the 50Ah cell offers cost advantages. To meet the capacity requirements, a 1P32S module configuration is adopted, ensuring system electrical compatibility and economic balance while effectively controlling costs. This paper takes a single 1P32S battery module in the residential battery energy storage system as the research object. Based on the electrical principle of the system, the connection method between each battery module and the high-voltage box is determined. The designed three-dimensional model of the residential battery energy storage system is presented in the following figure.
The assembly relationship is as follows: the base is at the bottom, fixed to the ground by bolts, ensuring safe system operation. The battery modules are stacked on the base, and during stacking, the module enclosure is positioned by a bottom recess. A high-voltage connector protection device is designed in the enclosure to avoid manual wiring, making the entire system easy and flexible to install, reducing overall system weight and size. The high-voltage box is installed on top of the battery modules, connecting the entire system in series.
Structural Design of the Residential Battery Energy Storage System
Module Design
As the basic building unit of the battery pack, the module dimensions determine the overall layout of the pack. The module consists of a Cell Contact System (CCS), lithium iron phosphate cells, end plates, steel straps, and rubber strips. The CCS is designed with temperature and voltage sensors to monitor cell status in real time, ensuring safe battery pack operation. A dual steel strap and dual metal end plate design are adopted to guarantee the safety and reliability of the cells throughout their life cycle. Rubber strips are filled between cells for cushioning and to improve cycle life.
Internal Layout of the Residential Battery Energy Storage System
Based on the module dimensions, the internal layout of the battery pack is designed. To prevent the risk of thermal runaway propagation, each pack is equipped with an aerosol fire suppression device, which responds quickly, is clean and environmentally friendly, and efficiently safe. When abnormal temperature is detected, it can suppress fire spread. To relieve the sudden internal pressure change caused by cell thermal runaway, an explosion-proof valve is installed at the rear of the enclosure to balance internal and external pressure difference and prevent explosion. High-voltage and low-voltage connectors are fixed on the left side of the enclosure for convenient connection to the module. The Battery Management Unit (BMU) is installed at the front end of the enclosure to reduce electromagnetic interference between high-voltage and low-voltage communication loops.
Finite Element Model Establishment of the Residential Battery Energy Storage System
Minor structural features of the residential battery pack have little influence on the dynamic characteristics of the simulation analysis but increase the probability of non-convergence of results. To prevent poor mesh quality and computational non-convergence, tiny features of the battery pack are simplified. In this paper, the three-dimensional design software is used to simplify the battery pack model, removing minor features that do not affect simulation accuracy, ensuring computational timeliness and accuracy.
The simplified battery pack model is imported into finite element simulation software for mesh generation. Sheet metal parts such as the top cover, lower enclosure, reinforcement ribs, crossbeams, and steel straps are meshed using Shell elements, with the thickness of each part determined by the actual dimensions from the original digital model. Cells and end plates are meshed using Solid elements. After meshing, connections between components are established, and corresponding element and material properties are assigned to the relevant parts, forming the finite element model of the residential battery energy storage system, as described in the following table summarizing the element types and material properties.
| Component | Element Type | Material | Young’s Modulus (GPa) | Poisson’s Ratio | Density (kg/m³) | Yield Strength (MPa) |
|---|---|---|---|---|---|---|
| Enclosure (Top cover, Lower box, Crossbeams, etc.) | Shell (Thickness assigned) | Steel (Q235) | 210 | 0.3 | 7850 | 235 |
| Steel Straps | Shell | Steel | 210 | 0.3 | 7850 | 235 |
| End Plates | Solid | Aluminum alloy | 69 | 0.33 | 2700 | 280 |
| Cells (LFP prismatic) | Solid (Orthotropic equivalent) | Equivalent material | E1=30, E2=30, E3=10 | 0.2 | 2200 | N/A (stress limited by electrode) |
| Rubber strips | Solid | Silicone rubber | 0.005 | 0.48 | 1200 | N/A |
| BMS/BMU (simplified as mass) | Lumped mass | — | — | — | — | — |
Sweep Vibration Simulation Analysis of the Residential Battery Energy Storage System
The finite element model obtained is input into the finite element simulation software to perform sweep vibration analysis on the residential battery energy storage system.
Modal Analysis
Because low-order frequencies have a significant impact on the structural strength of the battery pack, only low-order frequency information is studied. The first ten natural frequencies of a single module are calculated and listed in the table below, and the corresponding mode shapes are described. The first-order frequency is 41.02 Hz, effectively avoiding typical transportation frequencies (2–7 Hz for sea freight and 10–15 Hz for land freight). Thus, the structural reliability of the residential battery energy storage system meets requirements.
| Mode Order | Frequency (Hz) | Mode Shape Description |
|---|---|---|
| 1 | 41.02 | Bending of the module in the transverse direction (Y-axis) |
| 2 | 41.14 | Bending of the module in the longitudinal direction (X-axis) |
| 3 | 57.91 | Torsion of the module about the vertical axis |
| 4 | 58.37 | Second-order bending in Y-axis |
| 5 | 79.14 | Local mode of the top cover |
| 6 | 79.18 | Local mode of the lower enclosure |
| 7 | 80.33 | Combined bending and torsion |
| 8 | 81.78 | Higher-order local deformation |
| 9 | 89.10 | Crossbeam vibration |
| 10 | 105.26 | High-order global bending |
For a linear undamped system, the modal analysis solves the eigenvalue problem:
$$ \left( \mathbf{K} – \omega_i^2 \mathbf{M} \right) \boldsymbol{\phi}_i = \mathbf{0} $$
where \(\mathbf{K}\) is the stiffness matrix, \(\mathbf{M}\) is the mass matrix, \(\omega_i\) is the \(i\)-th natural angular frequency, and \(\boldsymbol{\phi}_i\) is the corresponding mode shape vector.
Sweep Vibration Analysis
Since lateral and longitudinal vibrations have relatively minor effects compared to vertical vibrations, only vertical sweep vibration of the battery module is simulated. The following constraints are applied to the battery pack model: all translational degrees of freedom at the system mounting holes are constrained in the lateral and longitudinal directions; rotational degrees of freedom are constrained in the vertical direction. Based on the modal analysis results, the modal frequency range is 0–200 Hz. A UN38.3 PSD (Power Spectral Density) profile is applied vertically at the mounting holes. The maximum stress results for the main components are obtained.
The maximum stress in the battery pack occurs near the module crossbeam, with a value of 156.2 MPa, while the maximum stress in the enclosure is 70.4 MPa. Both values are well below the material yield strength of 235 MPa, indicating that the battery system satisfies mechanical reliability requirements. The stress response under random vibration can be evaluated using the Miles equation for root-mean-square stress:
$$ \sigma_{\text{rms}} = \sqrt{ \int_{0}^{\infty} G(f) \, H(f) \, df } $$
where \(G(f)\) is the input PSD and \(H(f)\) is the frequency response function. The peak stress is then compared to the yield limit.
Sweep Vibration Experimental Validation of the Residential Battery Energy Storage System
Based on the designed configuration, the physical prototype of the residential battery energy storage system is manufactured. Modal tests and sweep vibration tests are conducted on the produced system.
Modal Test Validation
Eight triaxial acceleration sensors are attached to the battery module. Modal information is obtained using the moving hammer impact method. The measured resonance frequencies are 36 Hz, 75 Hz, and 99 Hz. Comparing with the simulation results from the modal analysis, the error between measured and simulated values is less than 10%, confirming that the battery module meets the transportation modal requirements.
| Mode Order (from test) | Measured Frequency (Hz) | Simulation Frequency (Hz) | Error (%) |
|---|---|---|---|
| 1 | 36 | 41.02 | 9.3 |
| 2 | 75 | 79.18 | 5.6 |
| 3 | 99 | 105.26 | 6.0 |
Sweep Vibration Test Validation
Vertical sweep vibration analysis is performed on the battery module using a vibration shaker. The vibration test frequency range is 0–200 Hz. Resistive strain gauges are used to collect stress values at key points of the battery module. The measurement points are arranged in locations where high stress is predicted by the simulation. The surface is ensured to be level and smooth before attaching the gauges. The measured maximum stress values are summarized in the table below.
| Component | Measured Max Stress (MPa) | Simulation Max Stress (MPa) | Error (%) |
|---|---|---|---|
| Enclosure | 66.8 | 70.4 | 5.3 |
| Module Crossbeam | 144.6 | 156.2 | 8.0 |
The measured maximum stress values are in good agreement with the simulation results, with errors below 10%. Both values are lower than the material yield strength, confirming that the design of the residential battery energy storage system is structurally reliable.
Conclusion
In this paper, a residential battery energy storage system is designed, and sweep vibration simulation analysis as well as experimental validation are conducted. The results demonstrate that the maximum stress obtained from tests on the residential battery energy storage system differs from simulation values by less than 10%, and both are well below the material yield strength. Therefore, the system meets the reliability requirements. Future work may focus on lightweight design and intelligent control strategies to further improve the comprehensive performance of the product. The successful integration of simulation and test methods provides a robust approach for the development of safe and reliable battery energy storage systems for residential applications.