Battery Pack Design: Maximizing Performance and Efficiency
Battery packs are likely a familiar concept if you own an electric vehicle or an energy storage system. Packs are responsible for storing energy to power these systems and are composed of interconnected cells that produce energy.
This article will describe the battery components and explore the EV generative design challenges associated with them, focusing on high-performance for electric vehicles. After providing an overview of battery technology, we will delve into a crucial tool for EV battery pack design: engineering simulation (CAE).
Thanks to recent advancements in CAE simulation technology that merge CAD and CAE data with Deep Learning, battery pack design engineers can now utilize new, cost-effective tools to optimize thermal management systems and crashworthiness.
Ultimately, this can assist engineers in designing superior battery packs for a more sustainable world.
How to Increase Battery Power and Battery Capacity
Two basic high-performance battery concepts are related to series and parallel arrangements.
What Is Battery Power?
Power refers to the rate at which a battery supplies or consumes energy. It is the ability of a battery to deliver electrical energy in a short amount of time. Power is typically measured in watts (W) or kilowatts (kW). High-power batteries can discharge quickly, making them suitable for applications that require bursts of energy, such as starting an electric vehicle or providing short-term high performance in electronic devices.
What Is Battery Capacity?
Capacity, on the other hand, represents the total amount of electrical energy a battery can store. Capacity is measured in ampere-hours (Ah) or milliampere-hours (mAh) and indicates how much energy a battery can provide over an extended period. Higher capacity batteries can store more energy and provide power for a more extended period before recharging. Battery cells can be arranged in series or parallel to increase battery power and capacity.
When battery cells are connected in series, the positive terminal of one cell is connected to the negative terminal of the next generation cell, effectively adding up their voltages. The total voltage across the series-connected cells is the sum of the individual cell voltages. This increases the overall voltage of the battery pack.
The power remains relatively constant when cells are connected in series; however, the voltage increases, enabling the battery to deliver higher output. Series connections are commonly used in electric vehicles (EVs) and other applications requiring higher voltage levels.
In this case, the positive and negative terminals are connected, respectively. In this configuration, the voltage remains the same as that of a single cell, but the capacity is additive. Parallel connections increase the overall capacity of the battery pack.
When cells are connected in parallel, the output remains relatively constant because the voltage doesn't change. However, the capacity increases, allowing the battery to provide energy for a longer time. Parallel connections are commonly used in applications where extended runtime is essential, such as energy storage and backup power supplies.
Different Battery Chemistries
Lithium-Ion and lead acid batteries represent two distinct worlds of energy storage.
Lithium-Ion (Li-Ion) batteries, lightweight and compact, show high energy density, powering our modern devices effortlessly.
Lead acid batteries have, in contrast, a heavy form and supply reliable energy to cars and backup systems.
As EV batteries, Acid Lead batteries are much heavier and bulkier than Lithium-Ion batteries. Electric Vehicles require lightweight and compact energy storage solutions to maximize their range and overall efficiency; therefore Lithium-Ion is the choice.
Hybrid Battery Packs
Hybrid battery packs refer to the combination of different types of batteries used together in certain hybrid vehicles, particularly hybrid electric vehicles and some plug-in hybrid electric vehicles. These hybrid battery systems are designed to maximize each battery's benefits while mitigating their limitations. The most common configuration in hybrid battery packs includes a combination of Lithium-Ion batteries and Nickel-Metal Hydride batteries.
Sub-Packs or Battery Modules
Battery packs are actually made up of smaller sections called battery modules (or sub-packs). These modules have fewer cells connected in series and parallel, which makes them safe to handle. If there are any issues, it's easy to replace a few cells in the battery modules without having to replace the entire main battery itself.
Thus, battery modules facilitate enhanced safety, modularity, and serviceability full sized batteries, as well as improved thermal management and overall battery performance. Manufacturers can deliver safer, more reliable, and easier-to-maintain energy storage solutions by dividing the battery pack into smaller, manageable sub-packs.
Battery Pack Design for Electric Vehicles - Components
The electric vehicle (EV) battery pack is a crucial component that stores and supplies energy to the vehicle's electric motor.
The combination and design of battery pack components may vary depending on the specific electric vehicle model and manufacturer. Battery technology is continuously evolving, and newer developments may lead to future changes in the composition and structure of electric vehicle battery packs.
Battery packs can vary depending on the EV model and manufacturer, but they generally consist of the following eight key battery components:
The basic building blocks of the battery pack are individual battery cells. These cells are usually cylindrical (e.g., Lithium-Ion 18650 cells) or prismatic in shape and contain a positive electrode (cathode), a negative electrode (anode), and an electrolyte. Lithium-ion batteries are commonly used in modern EVs due to their high energy density and reliability.
Battery Management System (BMS)
The BMS is essential to an EV battery pack as it monitors and manages individual battery cells. Its main functions include balancing cell voltages, monitoring temperature, controlling charge and discharge rates, and ensuring the safety and longevity of the entire battery itself. The BMS' communications system communicates with the vehicle's onboard computer to provide real-time data and status updates.
Battery Cooling System
EV battery packs generate heat during the charging and discharging processes. A designed battery cooling system is integrated into the pack to maintain optimal operating temperatures and prevent the battery and other components from overheating. Typically, this involves liquid or air cooling methods to dissipate heat efficiently and maintain battery performance.
The battery pack is enclosed in a battery protective casing or housing that shields the battery cells and the BMS from external influences such as water, dust, and physical damage. The enclosure is designed to ensure safety and durability.
Connectors and Wiring
High-quality electrical connectors and wiring are used to interconnect the battery cells and integrate them into the vehicle's powertrain system. These components must handle high currents and ensure minimal power losses.
Battery Thermal Management System
In addition to the cooling system mentioned earlier, a thermal management system may include additional elements of high-performance battery packs like thermal insulation, heat sinks, and temperature sensors.
It helps regulate the battery pack's temperature and ensures it operates within the optimal temperature range.
EV battery packs deliver high-voltage DC power, which needs to be regulated to match the voltage requirements of the vehicle's electric motor and auxiliary systems. A voltage regulator or DC-DC converter ensures that the battery voltage power output is stable and compatible with the rest of the EV's electrical system.
High Voltage Connector
The battery pack needs to be connected to the electric motor and other high-voltage components of the EV. A high-voltage connector provides a secure and reliable connection between vital components, allowing power to flow from the battery to the vehicle powertrain.
Cells Used in Battery Packs
Cylindrical cells are one of the most commonly used types of battery cells in battery packs. They have a tubular shape and are often referred to by their size designation, such as "18650" or "21700", indicating their dimensions in millimetres (e. g. 18mm diameter and 65mm height for "18650").
These cells are known for their robustness, high energy density, and good thermal performance. They are widely used in various industries, including electric vehicles or laptops.
Prismatic cells have a flat, rectangular shape, making them space-efficient and suitable for compact battery pack designs.
They come in different sizes and can be tailored to fit specific vehicle platforms, allowing for more flexibility in battery pack configurations. Prismatic cells are often chosen for their ease of integration, improved thermal conductivity, and potential cost savings in manufacturing.
Advanced Simulation Solutions for Battery Safety and Longevity
The design of batteries demands consideration for safety and durability. Advanced simulation solutions such as CAE (Computer-Aided Engineering) offer capabilities that align with industry standards. These simulations enable engineers to optimize battery housing designs and reinforcements, identifying potential weaknesses and vulnerabilities in the battery structure and battery pack arrangement.
This results in the creation of a robust battery pack capable of withstanding mechanical stress, vibrations, and impacts, thereby reducing the risk of safety hazards.
Furthermore, advanced simulations evaluate the battery's thermal behaviour. By simulating different thermal scenarios, engineers can design efficient cooling systems that dissipate heat effectively, ensuring the battery operates within a safe temperature range. These simulations also guarantee compliance with industry standards, ensuring that battery manufacturers meet the highest safety and quality requirements.
Battery durability is also crucial to ensuring long-term performance. Advanced simulations assess the behaviour of battery cells under different operating conditions, allowing engineers to predict cell degradation and identify possible failure points. This equips them to optimize the battery's chemistry and design for improved longevity.
Thanks to these tools, the battery industry can confidently advance towards developing safer, more durable, and high-performance energy storage solutions for a sustainable future. With the power of advanced simulation solutions, battery manufacturers can bring their products to market with the utmost confidence.
Deep Learning for Battery Pack Design
The exciting topic of Deep Learning prediction has already been extensively discussed elsewhere. The image shows a comparison of CAE with Deep Learning's predictive function that can be extended to all EV components.
The process described, for example, where a designer without specific crash simulation skills can obtain displacement and maximum force, is a game-changer compared to the usual lengthy lead time of hours between design conception and CAE verification.
Even more groundbreaking innovations, such as algorithms driving design changes, will be deployed soon!