Open Access
Issue
Int. J. Simul. Multidisci. Des. Optim.
Volume 15, 2024
Article Number 23
Number of page(s) 12
DOI https://doi.org/10.1051/smdo/2024020
Published online 23 October 2024

© A. Dhoke and A. Dalavi, Published by EDP Sciences, 2024

Licence Creative CommonsThis is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

1 Introduction

Two of the most critical variables contributing to the success of current EVs are high-capacity rechargeable batteries and lightweight materials [1]. Unlike lead-acid batteries in conventional automobiles, which are primarily used to start the engines, batteries in EVs perform extra roles and need additional protection against overheating and collisions. Expanding EV usage globally increases the likelihood of EVs being involved in collisions, and these new kinds of batteries may offer unique dangers. As a result, further research and development are required to improve battery protection systems in EVs, as they present new and distinct issues.

Typically, batteries are housed in modules. The battery units are safeguarded by multiple-layer shells. The number of battery pack varies with the types of the vehicle, and heavy commercial vehicles have 3–6 battery packs (Fig. 1). Typically, aluminium underbody protection is used, together with an “aluminum extrusion ring for crash absorption, a steel tub with flanges and inner walls for the battery modules, and a steel housing cover [3]. Battery casings are intended to address a variety of issues, including safety, thermal runway, electric discharge, and mechanical vibrations” [4].

While the robust vehicle exterior affords protection to the battery pack, the battery pack and its contents face the very real possibility of damage in the event of collisions, or even through falls during assembly and maintenance [6]. As a result, electric vehicle battery modules and packs must undergo a series of rigorous tests including crush, drop, and exposure to fire, immersion, and short circuit [7]. Battery pack enclosure is a container of battery in electric vehicles (Fig. 2), which plays an important role in protecting the battery [8]. Battery pack security and economy an important indicator of design and fabrication (Fig. 3). Traditional battery packs with aluminum casting mode made the vehicle heavy and the process complicated. To protect the environment and reserve energy, the development of the automotive industry more and more lightweight and low-cost [9].

Developing a battery enclosure with world-class energy density, while meeting structural requirements for vehicle crash and durability requirements has given research attention in industry and academia [11]. EV safety is a legitimate worry that is subservient to the battery pack. Mechanical properties, such as the ability to withstand deformation and vibrational frequencies, have a role in battery pack safety. The battery may malfunction and explode if it does not meet the practical criteria for its intended case. To extend the cruising range of electric vehicles, it is important to study the shape transformations and mechanical behavior of enclosures. A lighter vehicle is preferred since it frees up space for other components and increases the space for battery packs [12]. Modularity in the design of electric vehicles is shown in the case study by [3]. EVs, especially low-floor electric buses, have a weight distribution difficulty because of this; as a result, packing space is critical.

Therefore, light weighting of battery pack enclosure for EVs is considered as an important research direction. It is also crucial to enhance the range of EV as well as the complete battery pack enclosure life cycles. Battery Pack is the primary source of energy for Electric Vehicle (EV) and it demonstrates scope for innovation in the long run. Apparently, the research areas of EV and its battery design are still in a nascent stage and have slow growth.

This paper, a comprehensive design of reference baseline battery pack enclosure assembly with batteries and a novel structure of honeycomb battery pack design is proposed to study mechanical parameters like mass of battery pack, natural frequency, and deformation for generic gravity loading based on finite element simulation. In the first phase, baseline battery pack design is analyzed and the CAD model is validated through modal performance with physical testing data available from the literature. In the second phase, the validated baseline battery pack design is considered as a base to study the proposed lightweight design of a novel honeycomb battery pack for mechanical characteristics mass, vibrational performance, and strength in gravity loading.

In this paper, reviews the multi-material battery enclosure design optimization, the multi-technologies, and a proficient Battery Management System (BMS) for compact battery pack design used to lightweight battery pack enclosure design; the multi-objective optimization approach for distinctive parameters of battery pack enclosure design optimization by diverse manufacturing techniques [15]. Design and Simulation of Battery Enclosure for an Electric Vehicle Application is discussed including CAD model, Finite element analysis, and design gauge optimization [16]. Impact protection of the battery pack is discussed by considering finite element simulation [17]. This paper presents lightweight nature-inspired cellular structured designs as energy absorbers in crashworthiness applications for electric vehicles [18].

Multi-course teaching learning- based multi-objective optimization (MCTLBO) is discussed to optimize the energy storage systems for electric vehicles [19]. Random Vibration Analysis for a Battery Enclosure of an Electric Vehicle is discussed [20]. Strength and size optimization of light weight battery pack enclosure is discussed [21]. Vibration analysis of elctric battery pack enclosure using honeycomb structures is discussed [22].

thumbnail Fig. 1

Schematic of commercial electric truck [2].

thumbnail Fig. 2

Schematic of battery pack design [5].

thumbnail Fig. 3

Example of a CAD model of battery pack enclosure of electric vehicles representing its different parts [10].

2 Research problem

The battery pack enclosure assembly is exposed to different loadings like gravitational and vibrations during running conditions. Deformations due to various loading cases for the battery pack enclosure may result in a short circuit and the battery pack catching fire/exploding. The least natural frequency extracted in the modal analysis is critical from a random vibrations point of view and it should be maximized. As a result, the battery pack enclosure assembly should be stronger, more resistant to vibrations, and lower in weight. It is therefore critical to design and develop novel design optimization techniques for battery pack enclosures that prioritize performance enhancements such as minimizing maximum deformation for different loading directions, maximizing the least natural frequency caused by vibrations, and minimizing the enclosure's mass.

2.1 Structural design of baseline battery pack enclosure

The baseline computer-aided design, CAD data for battery packs enclosure from reference paper [10] is modelled in ANSYS along with its components like battery module for 18,650 Li-ion batteries as shown in Figure 4. Parameters for the design considered for modelling CAD in ANSYS software are as mentioned in Table 1.

The Baseline battery pack enclosure design consists of battery tray parameters like length (L), width (W), and height (H) also batteries will be mounted in the battery module slot. Battery module parameters like length (l), width (w) and height (h). The other parameters like battery tray wall thickness (tw), battery tray bottom thickness (tb), battery module bottom thickness (mb), battery module long wall thickness (mwl), and battery module wide wall thickness (mww) are also required to complete CAD modeling for baseline battery pack enclosure in ANSYS software.

Aluminum alloy material is defined to the baseline battery pack enclosure structure for its components of the battery tray and battery module. Its material parameters are mentioned in the Table 2.

thumbnail Fig. 4

The schematic diagram of baseline pack enclosure design with aluminium alloy [10].

Table 1

Design parameters for baseline battery pack enclosure in ANSYS [10].

Table 2

Material parameters of aluminum alloy for baseline battery pack enclosure [10].

2.2 Structural design of honeycomb battery pack enclosure

2.2.1 Honeycomb structure

Normally, honeybees arrange hexagonal cells (Fig. 5) into a structure called a honeycomb to store honey or pollen. These architectures have tremendous efficacy while being light and requiring little resources. Honeycombs were typically employed in sandwich panels because of their superior characteristics. Hugo Junkers originally proposed the idea of employing a honeycomb core among two face structures when subjected to loads such as static, dynamical contact, twisting, or shear.

thumbnail Fig. 5

Honeycomb cell terminology [13].

2.2.2 Honeycomb panel

Honeycomb gives increased strength and firmness to the structure not only due to the core but also due to the facing sheets as shown in Figure 6. This type of structure is called a panel which gives important advantages such as a high strength-to-weight ratio and high rigidity to weight ratio to the structure [13].

thumbnail Fig. 6

Honeycomb panel construction [13].

2.2.3 Honeycomb battery pack enclosure

Honeycomb battery pack enclosure is designed based on reference baseline battery pack enclosure parameters mention in Tables 3 and 4. In this design, the battery tray is designed with a honeycomb structure. A honeycomb structure is formed with a central core and top-bottom face sheet.

The overall parameter for the battery tray and battery module is the same as the reference baseline design. The battery tray is designed with a honeycomb structure with section parameters mention in Figure 7.

Honeycomb battery tray is design with material parameters listed in Table 3. Aluminum alloy material is considered for battery module same as baseline battery pack enclosure. Battery module specific material parameters are listed in Table 2.

Table 3

Design parameters for honeycomb battery pack enclosure in ANSYS.

Table 4

Material parameters for honeycomb tray [14].

thumbnail Fig. 7

The schematic diagram of honeycomb pack enclosure design.

2.3 Loading conditions for battery pack enclosure

While running the electric vehicle on the road, vibrational loading acts on the battery pack, and vibrational performance is measured by modal analysis. Also, the gravity loading for the battery is applied as the vertically downward force on the bottom of the battery module, the overall weight of the battery assembly is approximately 220 kg considered while designing the battery pack, and the value of the safety factor is set as 3.0. Battery pack enclosure assembly is mounted on the vehicle through battery lugs. All direction constrains are applied at center of 4 lifting lugs for all finite element analysis.

3 Research methodology

The research methodology considered to design honeycomb battery pack enclosure assembly is as mention in Figure 8. The put forward methodology is a step by step process for the design and CAD modeling in ANSYS software for finite element simulation.

In the first phase, the baseline battery pack enclosure assembly is designed in ANSYS software by considering the design parameters mentioned in the literature [10]. The baseline battery pack assembly design with Aluminium Alloy material shown in Figure. 4 is analyzed in ANSYS software for vibration loading to extract minimum natural frequency for the assembly structure with no battery mass and constrained all degrees of freedom at lug location. Parameters like mass of battery pack assembly, maximum deformation and minimum natural frequency for baseline battery pack design considered in this study are validated with same parameters mentioned in the literature [10]. These parameter validation and co-relation with tested data mention in literature [10] will give confidence on the accuracy of baseline battery pack enclosure assembly design considered in this study.

In second phase same design parameters are used for the honeycomb battery pack enclosure design. Battery tray for honeycomb design is designed in ANSYS using information mentioned in literature [14].

The finite element analysis is performed in ANSYS on battery tray of baseline and honeycomb design to compare modal performance for certain mass or weight of battery tray. Honeycomb battery tray modal performances also check for different core heights to understand behavior and to decide the final parameters for honeycomb battery pack enclosure design.

The finite element simulation is performed on both design of baseline battery pack enclosure assembly and the final honeycomb battery pack enclosure assembly for evaluating the mass, maximum deformation, and the minimum natural frequency in ANSYS software. Mass is the structural property and it depends on parameters like different thickness of battery modules, enclosure, and material density. The mass of structure is calculated using ANSYS software.

The final honeycomb battery pack enclosure design is selected and a comparative study is performed with baseline battery pack enclosure design based on mass, maximum deformation under gravity loading, and minimum natural frequency under vibrational analysis.

thumbnail Fig. 8

Procedure for generation of honeycomb pack enclosure design.

4 Results and discussion

The results of the minimum natural frequency under vibrational analysis for battery pack enclosure assembly design shows (Fig. 9) is 91.15 Hz and the maximum deformation is 2.07 mm. The mass for the battery pack enclosure assembly design is 15.71 kg. Table 5 shows battery pack enclosure assembly design consider in this study has a very close co-relation with the model mention in literature [10] with the percentage deviation of 3.59% for minimum natural frequency and a percentage deviation of 1.26% for mass of battery pack assembly. There is some higher deviation observed in terms of maximum deformation. These results co-relation will give confidence in baseline battery pack CAD, FE modelling and results accuracy considered in this study.

The results of minimum natural frequency under vibrational analysis for battery tray of honeycomb and baseline battery pack enclosure design. The baseline battery tray shows (Fig. 10) a minimum natural frequency of 3.19 Hz whereas the honeycomb battery tray shows (Fig. 11) a minimum natural frequency of 95.95 Hz. This is because the honeycomb battery tray has low mass and high stiffness in comparison to the baseline battery tray design. The mass for battery tray for the baseline and honeycomb design is 5.6 kg, 0.38 kg respectively.

The results of minimum natural frequency under vibrational analysis for battery tray of honeycomb design for different core height is summarized in Table 6. Honeycomb battery tray with 10 mm of core height shows (Fig. 12) a minimum natural frequency of 95.95 Hz whereas for 30 mm and 50 mm of core height shows (Figs. 13 and 14) a minimum natural frequency of 177.07 Hz and 211.45 Hz respectively. This is because stiffness increases as core height increases. The mass for honeycomb battery tray for these three different core height like 10 mm, 30 mm and 50 mm are 0.38 kg, 1.17 kg and 1.95 kg respectively.

Based on the results of different combinations for the honeycomb battery tray design, final design of the honeycomb battery tray is selected i.e. Battery tray with a 10 mm core height and with the material of aluminum 5052-H32 as the core and glass fiber as face sheet. This honeycomb battery tray with an aluminum alloy battery module is the proposed honeycomb battery pack enclosure design. The proposed honeycomb battery pack enclosure assembly design is analyzed and compares results with the baseline battery pack enclosure design.

The results of minimum natural frequency under vibrational analysis constrained at lug of baseline and honeycomb battery pack enclosure design shows (Fig. 15) 91.15 Hz and shows (Fig. 16) 119.15 Hz respectively. This is because of the mass and stiffness of the design. The mass of the baseline and honeycomb battery pack enclosure design is 15.71 kg and 10.5 kg respectively.

The results of maximum deformation and maximum stress level under gravity analysis for 220 kg of battery weight and constrained at lug of baseline battery pack enclosure design shows (Fig. 17) 2.07 mm and shows (Fig. 18) 138.0 MPa respectively.

The results of maximum deformation and maximum stress level under gravity analysis for 220 kg of battery weight and constrained at lug of honeycomb battery pack enclosure design shows (Fig. 19) 1.23 mm and shows (Fig. 20) 102. 8 MPa respectively.

Table 7 summaries the overall results for honeycomb battery pack design in comparison with the reference baseline design. The baseline design tray weight is around 5.4 kg whereas for honeycomb design tray weight is only 0.38 kg so the net weight reduction with the honeycomb tray design is around 5.22 kg. Baseline tray design frequency is 3.19 Hz whereas for honeycomb tray design frequency is 95.95 Hz. Baseline battery pack design weight is around 15.71 kg whereas for honeycomb battery pack design weight is only 10.5 kg so the net weight reduction with the honeycomb battery pack design is around 5.2 kg. Baseline battery pack design frequency is 91.15 Hz whereas for honeycomb battery pack design frequency is 119.15 Hz. Baseline battery pack design displacement and stress levels are 2.07 mm and 138.0 MPa respectively whereas for honeycomb battery pack design displacement and stress levels are 1.23 mm and 102.8 MPa respectively.

thumbnail Fig. 9

Modal result of battery pack enclosure assembly design.

Table 5

Parameters validation of baseline battery pack design with literature data.

thumbnail Fig. 10

Modal result of baseline battery tray design.

thumbnail Fig. 11

Modal result of honeycomb battery tray design.

Table 6

Effect of honeycomb core height on tray modal frequency.

thumbnail Fig. 12

Modal result of honeycomb for 10 mm core height.

thumbnail Fig. 13

Modal result of honeycomb for 30 mm core height.

thumbnail Fig. 14

Modal result of honeycomb for 50 mm core height.

thumbnail Fig. 15

Modal result of baseline battery pack enclosure design.

thumbnail Fig. 16

Modal result of honeycomb battery pack enclosure design.

thumbnail Fig. 17

Displacement plot of baseline battery pack design.

thumbnail Fig. 18

Stress plot of baseline battery pack design.

thumbnail Fig. 19

Displacement plot of honeycomb battery pack design.

thumbnail Fig. 20

Stress plot of honeycomb battery pack design.

Table 7

Result summary for honeycomb battery pack design.

5 Conclusions

In this study, a novel structural honeycomb battery pack enclosure is designed to contain batteries. Vibrational and static gravity characteristics are analyzed using finite element simulation. Baseline battery pack design is validated through physically tested data from the literature. This baseline battery pack design results further considered as a base to compare honeycomb battery pack design results. It is found that the baseline battery pack design weight is around 15.71 kg whereas for honeycomb battery pack design weight is only 10.5 kg so with the novel honeycomb battery pack enclosure design net weight reduction of around 5.2 kg is achieved. The modal frequency for the honeycomb battery pack is higher than the baseline design therefore honeycomb design shows much better modal performance for vibrational analysis. Honeycomb tray designs with different core height show better vibrational performance with increased try weight for with respect to increase core height. Stress and deformation in honeycomb battery pack design is reduced compared to baseline battery pack design therefore honeycomb battery pack design shows much better performance for gravity loading analysis. In conclusion, this light in weight novel structural honeycomb battery pack enclosure design demonstrates good vibrational and strength characteristics supporting its commercial potential and readiness.

Funding

This research received no external funding.

Conflicts of interest

The authors declare no conflict of interest.

Data availability statement

Not applicable.

Author contribution statement

Amol Dalavi: Conceptualization, methodology, proof reading, supervision, Review and Editing. Ashvin Dhoke: Software, validation, analysis, original draft preparation.

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Cite this article as: Ashvin Dhoke, Amol Dalavi, Optimal design of honeycomb battery pack enclosure for electric vehicle, Int. J. Simul. Multidisci. Des. Optim. 15, 23 (2024)

All Tables

Table 1

Design parameters for baseline battery pack enclosure in ANSYS [10].

Table 2

Material parameters of aluminum alloy for baseline battery pack enclosure [10].

Table 3

Design parameters for honeycomb battery pack enclosure in ANSYS.

Table 4

Material parameters for honeycomb tray [14].

Table 5

Parameters validation of baseline battery pack design with literature data.

Table 6

Effect of honeycomb core height on tray modal frequency.

Table 7

Result summary for honeycomb battery pack design.

All Figures

thumbnail Fig. 1

Schematic of commercial electric truck [2].

In the text
thumbnail Fig. 2

Schematic of battery pack design [5].

In the text
thumbnail Fig. 3

Example of a CAD model of battery pack enclosure of electric vehicles representing its different parts [10].

In the text
thumbnail Fig. 4

The schematic diagram of baseline pack enclosure design with aluminium alloy [10].

In the text
thumbnail Fig. 5

Honeycomb cell terminology [13].

In the text
thumbnail Fig. 6

Honeycomb panel construction [13].

In the text
thumbnail Fig. 7

The schematic diagram of honeycomb pack enclosure design.

In the text
thumbnail Fig. 8

Procedure for generation of honeycomb pack enclosure design.

In the text
thumbnail Fig. 9

Modal result of battery pack enclosure assembly design.

In the text
thumbnail Fig. 10

Modal result of baseline battery tray design.

In the text
thumbnail Fig. 11

Modal result of honeycomb battery tray design.

In the text
thumbnail Fig. 12

Modal result of honeycomb for 10 mm core height.

In the text
thumbnail Fig. 13

Modal result of honeycomb for 30 mm core height.

In the text
thumbnail Fig. 14

Modal result of honeycomb for 50 mm core height.

In the text
thumbnail Fig. 15

Modal result of baseline battery pack enclosure design.

In the text
thumbnail Fig. 16

Modal result of honeycomb battery pack enclosure design.

In the text
thumbnail Fig. 17

Displacement plot of baseline battery pack design.

In the text
thumbnail Fig. 18

Stress plot of baseline battery pack design.

In the text
thumbnail Fig. 19

Displacement plot of honeycomb battery pack design.

In the text
thumbnail Fig. 20

Stress plot of honeycomb battery pack design.

In the text

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