Project 1 Mechanical design of battery pack
PROJECT 01
MECHANICAL DESIGN OF BATTERY PACK
AIM: Prepare the detailed mechanical design of battery pack of the cell ANR26650M1-B along with its enclosure, which has the capability to produce 18kwh energy and state your assumptions.
ABSTACT: In this project, I will perform a comprehensive analysis to determine all the essential parameters needed for the construction of an electric vehicle (EV) battery pack. The selected cell for our battery pack is the ANR26650M1-B. Our analysis will encompass various electrical aspects, including temperature management, depth of discharge (DOD), operating current, energy density, work cycles, battery capacity, state of charge (SOC), state of health (SOH), and Ampere-hour (Ah) capacity.
Furthermore, I will also go through into the geometrical considerations, such as the battery pack's size, weight, volume, material used and surface area, to ensure it fits seamlessly into the intended application. These geometric parameters are crucial for space optimization and efficient integration within the EV.
To conclude, I will explore various enclosure models suitable for our battery pack, ensuring that it is well-protected and safely housed. Our objective is to carry out a thorough assessment of all these factors to design a high-performance and reliable EV battery pack tailored to meet specific requirements.
OBJECTIVES:
1) Gather data from the given Nano phosphate High Power Lithium-Ion Cell PDF for the ANR26650M1-B cell.
2) Figure out all the electrical and physical detailed specifications for an 18-kWh battery pack.
3) Determine the mathematical calculations and data required of the battery pack.
4) Pick the right protective case and materials for the battery pack based on the dimensions we calculate.
STEPS TO APPROACH:
1) To make a battery pack for an electric vehicle, we first need to work out how much power we need, which is 18 kWh given. This depends on the vehicle's power and motor requirements.
2) For an 18-kWh battery pack, I need to calculate how many cells I need to connect in parallel and in series to reach that power.
3) Once we know how to arrange the cells, we need to plan how they fit together in terms of shape and structure.
4) After assembling the cells, we must find a suitable case for the battery pack. This case should help with things like keeping the temperature right and protecting the battery from physical damage like dust and sand.
THEORY:
The ANR26650M1-B is a specific type of lithium-ion rechargeable battery cell. These cells are commonly used in vast applications, including power tools, electric vehicles, solar energy systems, and more. Here are some typical characteristics and information about ANR26650M1-B cells:
<!-- [if !supportLists]-->· Chemistry: These cells are usually based on lithium iron phosphate (LiFePO4) chemistry. LiFePO4 is known for its safety, long cycle life, and stable performance.
<!-- [if !supportLists]-->· Size: The "26650" in the name refers to the physical size of the cell. A 26650 cell is twenty-six millimeters in diameter and sixty-five millimeters in length.
· Capacity: The capacity of ANR26650M1-B cells can vary, but they are often available in capacities ranging from around 2,000mAh to 3,500mAh. The specific capacity may depend on the manufacturer and the intended application.
<!-- [if !supportLists]-->· Voltage: These cells typically have a nominal voltage of 3.2 volts.
<!-- [if !supportLists]-->· Applications: ANR26650M1-B cells are commonly used in applications where high energy density, long cycle life, and safety is essential. This includes electric vehicles, large flashlights, portable power banks, and other high-performance devices.
<!-- [if !supportLists]-->· C-rating: These cells also have a C-rating, which indicates the rate at which they can discharge their capacity. The C-rating is a crucial factor for high-power applications.
<!-- [if !supportLists]-->· <!--[endif]-->Safety: LiFePO4 batteries are considered safer than some other lithium-ion battery chemistries because they are less prone to thermal runaway and combustion.
<!-- [if gte vml 1]>
<!--[endif]--><!-- [if gte vml 1]><![endif]-->
<!-- [if gte vml 1]>
Series Connection: Battery cells are attached end to end, positive terminal to negative terminal, in a series connection. By doing this, the battery pack's overall voltage is raised but its capacity remains constant. To increase the pack voltage, which is necessary for an EV to have a suitable power output and range, cells are connected in series. A 32V pack with a total capacity of 200 Ah (same as a single cell) would be created, for instance, if ten 3.2V cells with a capacity of 200 Ah each were connected in series. In a series connection, the voltage of the cells increases but the capacity stays constant.
Parallel Connection: Positive terminal to positive terminal and negative terminal to negative terminal are used to connect battery cells in a parallel connection. By doing this, the battery pack's overall capacity improves while maintaining the same voltage. To improve the battery pack's capacity and extend the driving range, cells are connected in parallel. A 32V pack with a total capacity of 2,000 Ah (ten times the capacity of a single cell) would be created, for example, if ten 3.2V cells with a capacity of 200 Ah each were connected in parallel. The risk of one cell limiting the performance of the entire pack is decreased through parallel connections, which assist to guarantee that each cell distributes the burden.
Series-Parallel Hybrid Connection:
In many EV battery systems, both series and parallel connections are used to achieve the required balance between voltage and capacity. For example, you might connect groups of cells in parallel (to increase capacity) and then connect these groups in series (to increase voltage). This hybrid configuration provides the best of both worlds in terms of capacity and voltage.
<!-- [if gte vml 1]>
<!--[endif]--><!-- [if gte vml 1]><![endif]-->
PROCEDURE:
Begin with Cell Calculation: The initial step involves calculating the specifications and requirements for individual battery cells.
<!-- [if !supportLists]-->Ø <!--[endif]-->Establish Battery Pack Assumptions: Next, make certain assumptions regarding the overall configuration and characteristics of the battery pack based on the calculated cell parameters.
<!-- [if !supportLists]-->Ø <!--[endif]-->Perform Battery Pack Calculations: Utilizing the assumptions made, carry out detailed calculations to design the battery pack, considering factors like voltage, capacity, and power requirements.
<!-- [if !supportLists]-->Ø <!--[endif]-->Determine Battery Pack Surface Area: Using the dimensions and specifications of the individual cells, compute the surface area needed to accommodate the battery pack.
<!-- [if !supportLists]-->Ø <!--[endif]-->Construct the Battery Pack: Finally, based on the earlier calculations and surface area requirements, proceed to construct the battery pack to meet the intended specifications and performance criteria.
<!-- [if gte vml 1]>
<!--[endif]--><!-- [if gte vml 1]><![endif]-->
CALCULATIONS:
Assumptions:
<!-- [if !supportLists]-->Ø <!--[endif]-->Cell: ANR26650M1-B
<!-- [if !supportLists]-->Ø <!--[endif]-->Total Battery Pack Capacity: 18 kWh
<!-- [if !supportLists]-->Ø <!--[endif]-->Nominal Cell Voltage: 3.3 V
<!-- [if !supportLists]-->Ø <!--[endif]-->Cell Capacity: 2.5 Ah
Step 1: Calculate the Required Cell Capacity and Cell Energy
<!-- [if !supportLists]-->Ø <!--[endif]-->Total capacity (kWh) = Total voltage (V) x Total capacity (Ah)
18 kWh = Total voltage (V) x Cell capacity (Ah)
<!-- [if !supportLists]-->Ø <!--[endif]-->To find the required cell capacity:
Cell capacity (Ah) = 18 kWh / Total voltage (V)
Cell capacity (Ah) = 18,000 Wh / 400 V
Cell capacity (Ah) = 45 Ah
<!-- [if !supportLists]-->Ø <!--[endif]-->Cell energy = cell capacity (Ah) * cell nominal voltage (v)
= 2.5 * 3.3 = 8.25 Wh.
Step 2: Determine Series and Parallel Connections
<!-- [if !supportLists]-->Ø <!--[endif]-->Maintain a nominal voltage of around 400 V (assume) for electric vehicle applications.
<!-- [if !supportLists]-->Ø <!--[endif]-->Calculate the number of cells in series:
<!-- [if !supportLists]-->Ø <!--[endif]--> Number of cells in series = Total voltage (V) / Cell nominal voltage (V)
Number of cells in series = 400 V / 3.3 V ≈ 121 cells (round up to the nearest whole number)
<!-- [if !supportLists]-->Ø <!--[endif]-->Calculate the number of cells in parallel:
Number of cells in parallel = Required cell capacity (Ah) / Cell capacity (Ah)
Number of cells in parallel = 45 Ah / 2.5 Ah = 18 cells
Step 3: Calculate the Total Number of Cells
<!-- [if !supportLists]-->Ø <!--[endif]-->Total number of cells = Number of cells in series x Number of cells in parallel
Total number of cells = 121 cells x 18 cells = 2,178 cells
Now that we have the new cell configuration, let's calculate the other parameters:
Step 4: Calculate the Total Volume
<!-- [if !supportLists]-->Ø <!--[endif]-->Volume of single cell configuration = πr^2h = 3.14*0.013^2*0.065 = 0.0000344929 m^3
<!-- [if !supportLists]-->Ø <!--[endif]-->Total volume = Number of cells x Volume of a single cell
Total volume = 2,178 cells x 0.0000344929 m^3
Total volume ≈ 0.07527 m^3
Step 5: Calculate the Total Weight
<!-- [if !supportLists]-->Ø <!--[endif]-->Total weight = Number of cells x Weight of a single cell
Total weight = 2,178 cells x 0.076 kg (weight of a single cell)
Total weight ≈ 165.53 kg
Step 6: Calculate Energy Density
<!-- [if !supportLists]-->Ø <!--[endif]-->Energy density = Total capacity (kWh) / Total volume (m^3)
Energy density = 18 kWh / 0.07527 m^3
Energy density ≈ 238.99 kWh/m^3
Now, I have a battery configuration that uses 2,178 cells in a 121S/18P arrangement, resulting in a total capacity of approximately 18 kWh. I also calculated the total volume, weight, and energy density for this configuration.
PHYSICAL DESIGNING OF THE BATTERY PACK
In the production of electric vehicle batteries, the assembly process involves connecting individual battery cells using conductive busbars to create modules. Depending on the specific energy storage needs of the vehicle, these modules are combined, often within a sealed enclosure or pack. Multiple packs may then be integrated into a structural tray or directly into the vehicle chassis.
Irrespective of the size or style of battery packs and trays, the welding requirements remain consistent. Aluminum, a commonly used material in electric vehicle construction, poses a unique challenge for welding. Aluminum weld seams must be exceptionally strong, devoid of cracks or porosity, to withstand the rigorous mechanical forces associated with vehicle operation. For battery packs, achieving a hermetic seal is critical to prevent any harm to the battery cells contained within.
Manufacturers face the dual challenge of creating high-quality weld seams efficiently and consistently, as they produce a significant volume of batteries annually. Fiber laser welding has emerged as the preferred method for many leading electric mobility manufacturers. This technique offers several advantages, including the ability to produce robust aluminum welds with no structural flaws, such as cracks or porosity. Moreover, it is a faster, more reliable, and easily automated process compared to alternative welding methods.
<!-- [if gte vml 1]>
<!--[endif]--><!-- [if gte vml 1]><![endif]-->
<!-- [if gte vml 1]>
<!--[endif]--><!-- [if gte vml 1]><![endif]-->
Battery Pack Enclosure:
<!-- [if !supportLists]-->Ø <!--[endif]-->Material: Aluminum is a popular choice for EV battery pack enclosures due to its lightweight, strength, and heat dissipation properties, as well as corrosion resistance.
<!-- [if !supportLists]-->Ø <!--[endif]-->Design: The enclosure should be custom designed to accommodate the specific number and arrangement of cells. It should include proper ventilation for effective cooling and sealing to prevent moisture and contaminants from entering.
<!-- [if !supportLists]-->Ø <!--[endif]-->Modularity: A modular design can facilitate maintenance and replacement of individual modules within the pack, improving serviceability.
Battery cell holder design (top and bottom):
To ensure the safe and effective usage of cylindrical cells, such as batteries, a battery cell holder is essential. It is intended to maintain correct alignment while securely holding cells in place. By doing this, it achieves a variety of goals, such as:
<!-- [if !supportLists]-->Ø <!--[endif]-->Secure Cell Retention: A battery holder's major job is to keep the cells firmly in place. This keeps cells from moving or being removed accidentally and ensures their steady functioning inside the gadget.
<!-- [if !supportLists]-->Ø <!--[endif]-->Mechanical vibration damping: Battery holders are designed to dampen mechanical vibrations that could be experienced during a device's operation. This reduces the possibility of the cells and the machinery they power's physical harm.
<!-- [if !supportLists]-->Ø <!--[endif]-->Improved Thermal Management: In the holder, properly positioned cells designate improved thermal routes. This facilitates the effective removal of heat produced during battery discharge, which is essential for both the longevity of the cell and the security of the device.
<!-- [if !supportLists]-->Ø <!--[endif]-->Material Choice: High-temperature-resistant materials like polypropylene or nylon are frequently used to make battery holders. These materials were selected because they can endure temperatures between 80 and 100 °C, guaranteeing the holder's long-term functioning in a variety of applications.
<!-- [if gte vml 1]>
Design of Lower Battery Pack Case:
<!-- [if !supportLists]-->Ø <!--[endif]-->The lower case, made from lightweight aluminum, is a crucial component in an electric vehicle's battery pack assembly. It consists of a top cover and bottom cover that shield the battery pack from environmental contaminants and dust. The design of the pack cover utilizes 0.5mm thick aluminum for a balance of protection and weight efficiency. The bottom cover specifically shields the lower battery holder.
Pack Cover:
<!-- [if !supportLists]-->Ø <!--[endif]-->Material: For the pack cover, aluminum or lightweight plastic materials are suitable.
<!-- [if !supportLists]-->Ø <!--[endif]-->Design: The cover should be securely attached to the enclosure to shield the cells from dust, debris, and environmental elements. It should also be designed for easy removal during maintenance and inspections.
Clips and Connectors:
<!-- [if !supportLists]-->Ø <!--[endif]-->Material: Copper or copper alloys are commonly chosen for conductive clips and connectors due to their low electrical resistance and reliability.
<!-- [if !supportLists]-->Ø <!--[endif]-->Design: Ensure that the clips and connectors are designed with ease of assembly and disassembly in mind. They should be insulated effectively to prevent short circuits.
Modular Design:
<!-- [if !supportLists]-->Ø <!--[endif]-->A modular design can facilitate the straightforward replacement of malfunctioning cells or modules, enhancing maintenance and reducing long-term costs.
<!-- [if gte vml 1]>
Thermal Management:
<!-- [if !supportLists]-->Ø <!--[endif]-->Implement an efficient cooling system, such as liquid cooling, to regulate the temperature of the battery pack. Effective cooling contributes to prolonged battery life and sustained performance.
Safety Features:
<!-- [if !supportLists]-->Ø <!--[endif]-->Integrate safety features, including fuses, disconnect switches, and thermal monitoring systems, to prevent overheating and short-circuits, enhancing the safety of the battery pack.
Cost-Effective Solutions:
<!-- [if !supportLists]-->Ø <!--[endif]-->Keep costs in check by selecting cost-effective materials and manufacturing methods that meet safety and performance requirements without compromising quality.
Testing and Certification:
<!-- [if !supportLists]-->Ø <!--[endif]-->Ensure that the battery pack design adheres to safety standards and undergoes rigorous testing for quality and safety. Comprehensive testing should encompass electrical, thermal, and impact assessments to guarantee reliability.
CONCLUSION/RESULTS
|
PARAMETERS CALCULATED |
VALUE ATTAINED |
|
TOTAL NUMBER OF CELLS |
2,178 cells |
|
CELL WEIGHT |
0.076 kg |
|
CELL VOLUME |
0.0000344929 m^3 |
|
VOLTAGE |
400V |
|
CELL CAPACITY |
45Ah |
|
TOTAL VOLUME |
0.07527 m^3 |
|
TOTAL ENERGY DENSITY |
238.99 kWh/m^3 |
|
TOTAL WEIGHT |
165.53 kg |
|
TOTAL BATTERY PACK CAPACITY |
18kwh |
The complete analysis and calculations have been made according to the assumptions for 18kwh battery pack and final values displayed above.
REFERENCES
https://www.buya123products.com/goodsdetail.php?i=6
https://ars.els-cdn.com/content/image/1-s2.0-S2212827120301797-gr1.jpg