Innovation and design of the battery box for electric vehicles

This summary is based on the Master Thesis "Innovation and design of the battery box for electric vehicles" published by "Faculty of Mechanical Engineering TUL".

Figure 31 : An exploded view of CSP's multi-material battery enclosure [23]

1. Overview:

Title: Innovation and design of the battery box for electric vehicles
Author: Bc. Chyva Hout
Year of publication: 2024
Journal/academic society of publication: Faculty of Mechanical Engineering TUL
Keywords: Battery box, design and innovation, electric vehicles, thermal management systems, concepts, AHP

2. Abstract:

This master's thesis concentrates on innovating and designing the new battery box for electric vehicles. The initial section of the thesis commences with a literature review to outline the current theme of electric vehicles using lithium-ion batteries, providing a comprehensive understanding of thermal management systems and the selection of materials for constructing battery boxes. Moreover, the initial section also involves investigating and examining information regarding the current status and ideas related to battery boxes found in both patent and non-patent databases. Subsequently, five conceptual designs were developed, each accompanied by an explanation and illustrated sketches detailing its technical system. The ultimate concept was chosen based on specific criteria using the AHP (Analytic Hierarchy Process) method to facilitate the creation of the 3D model. The final section utilizes numerical simulations to compute the temperatures generated by prismatic battery cells within the enclosure. This thesis also includes drawing of the final concept and parts of selected system components.

3. Introduction:

The promotion of the Electric Vehicles (EVs) industry is a primary focus for many governments aiming to reduce crude oil dependency and CO2 emissions. This trend has led to a significant increase in EV production and demand, as electromobility is a mature alternative propulsion technology. Central to EVs are energy storage systems, particularly the battery pack, which is the main power source. These packs, typically using Lithium-ion rechargeable batteries, consist of modules with numerous cells. During operation, battery packs endure harsh conditions like vibrations and shocks, making their safety and mechanical integrity (resistance to deformation and vibration) crucial for overall vehicle safety. Lighter-weight vehicles are preferred for increased range and battery pack life cycle.
Research and development (R&D) efforts are concentrated on cell electrode materials, thermal design of battery packs, charging configurations, infrastructure, and battery state estimation (e.g., State of Charge - SOC, State of Health - SOH). A major challenge is temperature management, as batteries generate heat due to the Joule effect and chemical reactions. Inadequate heat dissipation can impair performance, shorten lifespan, and pose safety risks like thermal runaway. It's recommended that battery temperatures remain below 50 °C for safe operation.
Cost is another vital design criterion, influenced by battery cells and assembly processes. While cell prices are set by manufacturers, assembly costs depend on battery pack design. Therefore, material selection and component design are significant for the cost-effectiveness of battery modules and packs, aiming for low cost while maintaining high performance and safety.

4. Summary of the study:

Background of the research topic:

The increasing adoption of electric vehicles (EVs) necessitates advancements in battery technology, particularly in the design and innovation of battery boxes. The battery box is a critical component, housing the Li-ion battery pack and ensuring its safety, thermal stability, and structural integrity under various operating conditions. Effective thermal management is paramount to prevent overheating and thermal runaway, while material selection influences weight, cost, and durability.

Status of previous research:

The literature review covered thermal management systems (active and passive cooling, heating), material selection for battery packs (metals like steel and aluminum, plastics, and composites), thermal runaway phenomena and mitigation (thermal barriers at module and cell levels), vibration isolation, and battery pack placement strategies.
Patent research indicated active development in areas such as using composite components, organic materials, sealants, enhancing explosion/impact resistance, integrating cooling subsystems, and developing theft-resistant batteries. Key innovation potentials identified from patents include the use of fibers, transparency, fragmentation, automation, pulsation, and symmetry. China is a leading country in patent applications for EV battery boxes.
Non-patent research revealed diverse battery box concepts and materials in the market, with a growing trend towards multi-material approaches using non-metallic materials to reduce weight. Modular designs for covers and battery subsystems are also prevalent. Developing robust test facilities is seen as a critical innovation opportunity.

Purpose of the study:

The goal of this Master Thesis is to explore innovative design strategies for a new battery box in electric vehicles, with a primary focus on achieving a lightweight design. This involves thoroughly exploring materials to develop a light battery box, aiming to optimize overall weight without compromising structural integrity or safety. The study includes an in-depth investigation into the current status of battery boxes for electric vehicles, exploring existing designs, materials in use, problem areas, and manufacturing processes. By synthesizing this information, the aim is to identify challenges and opportunities for improvement, generate five innovative conceptual designs for battery boxes, select the best ultimate concept for creating a detailed 3D model, and utilize numerical simulation techniques to calculate and analyze the temperature distribution within the 3D model of the final battery box concept.

Core study:

The core study involved several stages:

A comprehensive literature review on EV battery boxes, lithium-ion batteries, thermal management systems, and material selection.
An investigation and analysis of information from patent and non-patent databases regarding current battery box designs, materials, challenges, and innovations.
The development of five distinct conceptual designs for an EV battery box, each detailed with construction design, material selection, thermal management strategy, and illustrative sketches.
Selection of the optimal concept (Concept 2) using the Analytic Hierarchy Process (AHP) based on predefined criteria (lightweight, electrical insulation, safety, cost, modular design).
Creation of a detailed 3D model of the selected battery box concept (Concept 2), which features a composite carbon fiber construction, liquid cooling, and houses 12 battery modules (each with 10 Samsung SDI 94 Ah prismatic cells).
Performance of Finite Element Method (FEM) numerical simulations using ANSYS software to analyze the temperature distribution within the 3D model of the final battery box concept under specified thermal boundary conditions.

5. Research Methodology

Research Design:

The research was designed as a multi-stage process:

Literature Review: To establish a foundational understanding of EV battery boxes, lithium-ion battery characteristics, thermal management principles, and material selection criteria.
Current State Analysis: Exploration of patent databases (ESPACENET, USPTO, WIPO, Patent Inspiration, Google Patents, Global Dossier, Google Scholar) and non-patent sources (Google search, manufacturer web pages, technical articles) to identify existing solutions, trends, and problem areas.
Conceptual Design: Generation of five innovative conceptual designs for the battery box, detailing their technical systems and illustrating them with sketches.
Concept Selection: Application of the Analytic Hierarchy Process (AHP) method to evaluate the five concepts against a set of predefined criteria and select the most promising design.
Detailed Design and Modeling: Creation of a detailed 3D model of the selected battery box concept using Autodesk Inventor Professional 2022.
Numerical Simulation: Utilization of Finite Element Method (FEM) via ANSYS software to conduct thermal analysis and predict temperature distribution within the designed battery box.
Documentation: Preparation of drawings for the final concept and selected system components.

Data Collection and Analysis Methods:

Data Collection:

Literature Review: Academic papers, journals, handbooks, and conference proceedings related to EV batteries, thermal management, and materials.
Patent Databases: Searched using keywords (e.g., „BATTERY BOX“ AND (ELECTRIC) VEHICLE, „BATTERY PACK“, etc.) and Boolean logic operators in databases including ESPACENET, USPTO, WIPO, Patent Inspiration, Google Patents, and Global Dossier.
Non-Patent Databases: Google Scholar, web pages of manufacturers and users, technical magazines, and industry reports.

Analysis Methods:

Qualitative Analysis: For literature review and interpretation of patent/non-patent information to identify trends, challenges, and opportunities.
Analytic Hierarchy Process (AHP): Used for multi-criteria decision-making to select the final battery box concept. This involved pairwise comparison of criteria and then pairwise comparison of concepts against each criterion.
3D CAD Modeling: Autodesk Inventor Professional 2022 was used for the detailed design of the selected concept.
Finite Element Method (FEM) Simulation: ANSYS software was employed for steady-state thermal analysis to simulate temperature distribution within the battery box under defined boundary conditions.

Research Topics and Scope:

The primary research topic is the innovation and design of a new battery box for electric vehicles, with a strong emphasis on achieving a lightweight design without compromising safety or structural integrity.
The scope of the research includes:

A comprehensive review of literature on EV battery boxes, lithium-ion batteries, thermal management systems (active, passive, heating, cooling), and material selection (metals, plastics, composites).
Exploration and analysis of current designs, materials, problem areas, and manufacturing processes from patent and non-patent databases.
Identification of challenges and opportunities for improvement in battery box design.
Generation of five innovative conceptual designs for battery boxes.
Selection of the optimal concept using the AHP method.
Creation of a detailed 3D model of the selected concept.
Numerical simulation (FEM) to analyze the temperature distribution within the 3D model of the final battery box concept, considering heat generated by prismatic battery cells.
Inclusion of drawings of the final concept and selected system components.

6. Key Results:

Key Results:

Literature and Database Review: The study confirmed the critical role of thermal management and appropriate material selection for EV battery box performance, safety, and longevity. Patent analysis revealed China as a leading innovator in this domain, with key development directions including composite materials, improved impact resistance, and integrated cooling. Non-patent research highlighted a trend towards multi-material, often non-metallic, approaches for lightweighting and modularity.
Conceptual Design and Selection: Five distinct battery box concepts were developed. Using the Analytic Hierarchy Process (AHP), Concept 2 was selected as the most suitable option for further development, scoring highest against criteria including lightweight, electrical insulation, safety, cost, and modular design.
Final Design (Concept 2): The selected battery box is designed using composite material (specifically carbon fiber) to achieve significant weight reduction while maintaining robust strength, impact resistance, and durability. The thermal management system incorporates an aluminum liquid cooling plate and thermal pad-grade silicon (thermal conductivity of 1 W/m.K). The box is designed to accommodate 12 battery modules, each containing 10 Samsung SDI 94 Ah prismatic battery cells, resulting in a total of 120 cells and an energy capacity of 41.4 kWh.
FEM Simulation Outcomes: The numerical simulation of Concept 2 under specified boundary conditions (battery cell peak temperature of 50°C, ambient 22°C, external 20°C, coolant 16.5°C) showed:
- The internal temperature of the battery enclosure ranges from a maximum of 54°C to a minimum of 4.5506°C.
- The highest temperature observed externally on the battery box was 23.333°C.
- The most elevated temperature field was within the battery module, due to direct interaction with the battery cells.
- The integration of the cooling plate effectively lowered the temperature within the module from its peak of 54°C, stabilizing at approximately 28°C in the lower section of the battery box.
- The thermal pad successfully obstructed thermal conductivity among the battery cells housed within the module.

Figure Name List:

Figure 28 : Current technical solutions for battery boxes [20]

Figure 29 : Multi-material battery enclosure from LION Smart [21]

Figure 48 : The boundary condition for Samsung battery SDI 94 Ah

Figure 1 : Sources of heat in a lithium-ion battery [8]
Figure 2 : Lithium-ion cell temperature ranges [8]
Figure 3 : HEV temperature example [8]
Figure 4 : Active air cooling schematic [8]
Figure 5 : Passive air cooling schematic [8]
Figure 6 : Liquid cooling plates [8]
Figure 7 : Heat sink fins [8]
Figure 8 : All cell phase change composite (PCC™) material [8]
Figure 9 : A robust battery pack with one battery module in each compartment [10]
Figure 10 : A cylindrical battery cell assembly with cell spacers [11]
Figure 11 : Nissan Leaf battery pack [14]
Figure 12 : Placement of lithium ion battery pack in Nissan Leaf [15]
Figure 13 : Number of patent documents over time (QUERY: "BATTERY BOX" AND VEHICLE, 1981 documents, 1 per patent family) [18]
Figure 14 : Geographical analysis of applicants for patent documents (QUERY: "BATTERY BOX" AND VEHICLE, 1981 documents, 1 per patent family) [18]
Figure 15 : Document CN213782095U [19]
Figure 16 : Document US2021323418A1 [19]
Figure 17 : Document US2021305544A1 [19]
Figure 18 : Document KR20210036205A [19]
Figure 19 : Document KR101289562B1 [19]
Figure 20 : Document US2021260978A1 [19]
Figure 21 : Document CN113314783A [19]
Figure 22 : Document CN213936386U [19]
Figure 23 : Materials cited in patent documents (QUERY: "BATTERY BOX" AND VEHICLE, 1981 documents, 1 per patent family) [18]
Figure 24 : Number of patent documents for each material [18]
Figure 25 : Problem areas cited in patent documents (QUERY: "BATTERY BOX" AND VEHICLE, 1981 documents, 1 per patent family) [18]
Figure 26 : Number of patent documents for each problem [18]
Figure 27 : Evolutionary potential analysis in patent documents (QUERY: "BATTERY BOX" AND VEHICLE, 1981 documents, 1 per patent family) [18]
Figure 28 : Current technical solutions for battery boxes [20]
Figure 29 : Multi-material battery enclosure from LION Smart [21]
Figure 30 : Battery box from TRB group [22]
Figure 31 : An exploded view of CSP's multi-material battery enclosure [23]
Figure 32 : VARI technology for carbon fiber battery box [24]
Figure 33 : Kautex Textron and Lanxess all plastic battery housing [25]
Figure 34 : Battery box from SABIC concept [26]
Figure 35 : Concept 1
Figure 36 : Concept 2
Figure 37 : Concept 3
Figure 38 : Concept 4
Figure 39 : Concept 5
Figure 40 : Battery box from composite material
Figure 41 : Battery box body from composite material
Figure 42 : Components inside the battery box
Figure 43 : Battery module
Figure 44 : Components inside the battery module
Figure 45 : Crash structure
Figure 46 : Cooling plate
Figure 47 : Model with distinct materials assigned to different parts in ANSYS
Figure 48 : The boundary condition for Samsung battery SDI 94 Ah
Figure 49 : The boundary condition for environment convection
Figure 50 : The boundary condition for the temperature outside the battery box
Figure 51 : The boundary condition for the coolant temperature
Figure 52 : Mesh generation
Figure 53 : The temperature field outside the battery modules with the cooling system
Figure 54 : The temperature field of the upper surface cooling plate contact with battery modules
Figure 55 : The temperature field of the lower surface cooling plate contact with battery modules
Figure 56 : The temperature field inside the battery box
Figure 57 : The temperature field of cross-section inside the battery box
Figure 58 : The temperature field of the thermal pad between battery cells

7. Conclusion:

This Master's Thesis focused on the innovation and design of a new battery box for electric vehicles, with the primary goal of achieving a lightweight design. This was pursued through a comprehensive investigation of materials to construct a resilient, functional, and significantly lighter battery box.
The initial part of the work involved a thorough literature review of electric vehicle (EV) battery boxes using lithium-ion batteries, emphasizing thermal management and material selection. Key aspects included the significance of thermal management for battery performance and safety, factors influencing heat generation, and current thermal management solutions. The study also explored the current status and innovative ideas from patent and non-patent databases, noting China's significant patent activity and the market trend towards multi-material (often non-metallic) approaches for weight reduction.
Following this review and information compilation, five conceptual designs were developed. The Analytic Hierarchy Process (AHP) was employed for analysis, leading to the selection of Concept 2 as the preferred choice.
The battery box of Concept 2 is designed with composite material, specifically carbon fiber, to reduce weight while maintaining robust strength. It exhibits excellent impact resistance, effective thermal conductivity, durability, and a prolonged lifespan. Its thermal management system includes an aluminum liquid cooling plate and a thermal pad-grade silicon (1 W/m.K thermal conductivity). The pack houses 12 battery modules, each with 10 Samsung SDI 94 Ah battery cells, totaling 120 cells and an energy capacity of 41.4 kWh.
Simulation results for Concept 2 indicated an internal temperature range from a maximum of 54°C to a minimum of 4.5506°C under specified boundary conditions (with the battery cell temperature set to a peak of 50°C). The highest external temperature was 23.333°C. The most elevated temperature field was within the battery module, primarily due to direct interaction with the cells. The cooling plate integration proved efficient, reducing the module's peak temperature of 54°C to a stabilized 28°C in the lower section of the battery box. Furthermore, the inclusion of a thermal pad effectively impeded thermal conductivity among the battery cells within the module.

8. References:

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[8] John Warner (2015). Handbook of Lithium-Ion Battery Pack Design, chemistry, Components, Types and Terminology, pp. 115-128, 133-135.
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[15] America NN. Nissan Leaf Battery Pack.
[16] L. Brooke, Chevrolet Volt development story of the pioneering electrified vehicle training, 2012 (2011), pp. 03-12.
[17] N. Chambers, Chevy Volt and Nissan LEAF earn top marks on crash testsPluginCars: Recargo, Inc (2011).
[18] QUERY: "BATTERY BOX" AND ELECTRIC VEHICLE. In Patent Inspiration. Available from: https://app.patentinspiration.com/#report/E57FA8D843A6/filter.
[19] Google Patents. Available from: https://patents.google.com/.
[20] Electric Vehicle Magazine. Available from: https://chargedevs.com/newswire/consortium-of-auto-suppliers-launches-multi-material-ev-battery-casing-project/.
[21] Multi-Material Battery Enclosure From LION SMART. Available from: https://lionsmart.com/en/multi-material-hv-battery-enclosure/#after_section_1.
[22] Battery Box From TRB Group. Available from: https://www.compositesworld.com/articles/ev-battery-enclosure-inspires-material-process-innovations.
[23] Battery Enclosure Concept Multi-Material from continental Structural Plastics (CSP, Auburn Hills, Mich., U.S.). Available from : https://www.compositesworld.com/news/continental-structural-plastics-named-pace-pilot-finalist-for-multi-material-battery-enclosure-concept.
[24] Research on the design process of car carbon fiber battery box. Available from: https://inf.news/en/auto/fbf1bf8682c2157db3a0e9f9ee97d716.html.
[25] Kautex Textron and specialty chemical manufacturer Lanxess collaborated in a demonstration project to develop an all-plastic EV battery housing. Available from: https://www.plasticsmachinerymanufacturing.com/injectionmolding/article/21254768/plastics-trim-ev-batteries-weight-boost-safety.
[26] Glass-Fiber PP EV Battery Pack Could Debut in 2024. Available from: https://www.plasticstoday.com/automotive-mobility/glass-fiber-pp-ev-battery-pack-could-debut-in-2024.

9. Copyright:

This material is a paper by "Bc. Chyva Hout". Based on "Innovation and design of the battery box for electric vehicles".
Source of the paper: Master Thesis, Faculty of Mechanical Engineering TUL (DOI Not Provided in Document)

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Tags: Air cooling; , Applications; , CAD; , Cooling Plate; , Electric vehicles; , Heat Sink; , Lithium-ion battery; , Review; , temperature field