Understanding VDA Cell and module dimensions: Standardization for Electric Vehicles
Jinesh Vinayachandran
Technical Trainer & EV Specialist | HV Safety Professional I Battery Pack Development | Fuel Cell & Hydrogen Vehicle | Bridging Industry & Academia I
Electric vehicles (EVs) are rapidly transforming the automotive landscape, driving us towards a greener and more sustainable future. At the heart of this transformation lies the battery, a critical component that determines the performance and reliability of EVs. One significant development in this field is the standardization of VDA battery cells. But what exactly are VDA batteries, and why is their standardization so important?
What is VDA?
The Verband der Automobilindustrie (VDA), or the German Association of the Automotive Industry, is an organization that represents the interests of the German automotive industry. VDA plays a crucial role in setting standards and guidelines to ensure the interoperability and efficiency of automotive components, including batteries.
Why Standardize Battery Sizes?
In the past, EV manufacturers used a variety of battery cell sizes and formats, leading to inefficiencies in charging, maintenance, and overall battery system performance. To address these issues, VDA introduced standardized battery cell sizes. The primary goals of this standardization are:
Improving Interoperability: With a unified specification, batteries from different manufacturers can be interchangeably used in EVs of different brands. This reduces maintenance and replacement costs and enhances the convenience for users.
Enhancing Battery Performance: Standardized sizes allow for better optimization of battery structures, improving energy density and driving range. This makes EVs more appealing and capable of meeting diverse travel needs.
Reducing Manufacturing Costs: Standardization enables mass production of battery cells, lowering production costs. This can translate into more affordable EV prices, accelerating market adoption.
Standard Sizes of VDA Batteries
VDA prismatic cells come in several standardized sizes, ensuring compatibility and performance across different applications. Here are the common standard sizes:
These standardized dimensions help streamline the manufacturing process and ensure that batteries meet high-performance requirements.
Why Prismatic cells including pouch? Why not cylindrical?
Cylindrical cells, such as the popular 18650 and 21700 formats, have been standardized for many years, primarily due to their widespread use in consumer electronics and power tools. This standardization has led to well-established manufacturing processes and supply chains for cylindrical cells.
In contrast, prismatic and pouch cells were not as standardized, especially in the automotive industry. The VDA saw the need to create standardized dimensions for these cell formats to address several key issues:
Interoperability: Standardizing prismatic and pouch cells allows for easier integration across different vehicle models and manufacturers, promoting compatibility and reducing costs.
Optimization: Standard sizes help optimize the design and packaging of battery packs, improving energy density and overall vehicle performance.
Manufacturing Efficiency: Standardization enables mass production, reducing manufacturing costs and simplifying the supply chain.
By focusing on prismatic and pouch cells, the VDA aimed to bring the same level of standardization and efficiency to these formats as already existed for cylindrical cells, thereby enhancing the overall development and deployment of electric vehicle batteries.
Is Standardization Helpful?
The implementation of VDA cell standard sizes has had a profound impact on the EV market:
Increasing Electric Vehicle Options: Standardized sizes allow manufacturers to flexibly choose battery suppliers, fostering competition and encouraging continuous quality improvements.
Reducing Maintenance and Replacement Costs: Standardized cell sizes make battery maintenance and replacement more economically efficient. Vehicle owners can easily find suitable batteries, and repair services can offer competitive prices.
Driving Market Growth: Improved interoperability and performance standards attract more consumers to consider EVs, reducing greenhouse gas emissions and advancing sustainable transportation.
Additional Details
Aluminium Cell casing: VDA prismatic cells typically have an outer case made from aluminium, providing durability and helping maintain the cell's performance over time.
Pressure Requirements: These cells require pressure to be applied to their main faces to maintain optimal performance. This helps keep the layers of the cell intact and functioning efficiently over their lifetime
Initial Pressure: When assembling prismatic cells into a module, an initial pressure is applied to ensure proper contact between the cell layers. For a typical 12-cell module made using PHEV2 format prismatic cells (148mm x 91mm x 26.5mm), the initial force applied to the end plates is approximately 3 kN. This translates to a pressure of about 2.23 bar.
End-of-Life Pressure: As the cells age and undergo numerous charge-discharge cycles, the pressure requirement increases. At the end of life, the force can increase to around 30 kN, resulting in a pressure of approximately 22.3 bar.
Maintaining this pressure is crucial for the longevity and performance of the cells, as it helps prevent the layers from delaminating and ensures consistent electrical contact.
VDA355
The VDA355 standard ensures that battery modules are compatible with different automotive platforms, emphasizing modularity, safety, performance, and quality. This standard helps ensure interoperability and safety between different manufacturers and platforms within the automotive industry.
Applications
The VDA355 module is suitable for various new energy passenger cars and commercial vehicle battery packs. It can also be used in energy storage, ships, VGA, mining machinery, and other application scenarios.
Benefits of VDA355 Standardization
Interoperability: Ensures that battery modules can be used in standardized battery systems, making integration into electric vehicles (EVs) and hybrid electric vehicles (HEVs) easier.
Safety: Provides specific requirements for battery module design and construction, including dimensions, electrical characteristics, thermal management, and safety features.
Quality Assurance: Ensures that batteries are safe, fit for purpose, and work well regardless of the manufacturer.
ISO wanted to have a similar cell standard for electromobility and started creating one. ISO/IEC PAS 16898:2012 specifies a designation system as well as the shapes and dimensions for secondary lithium-ion cells for integration into battery packs and systems used in electrically propelled road vehicles including the position of the terminals and any over-pressure safety device (OPSD).
It is related to cylindrical, prismatic and pouch cells. The cell dimensions listed in ISO/IEC PAS 16898:2012 are recommended but not restricted for use in passenger cars up to 3.5 tonne. The inner design, the cell chemistry, the electrical characteristics and any further properties of the cells are not defined in ISO/IEC PAS 16898:2012. This standard is now currently listed as withdrawn in the ISO website.
In conclusion, the VDA cell standard size is a significant initiative in the EV field, contributing to improved battery interoperability, performance, and reduced manufacturing costs. As the EV market continues to evolve, the VDA cell standard size will play a crucial role in promoting environmentally friendly transportation and positioning EVs as a dominant force in future mobility.
Source:
(1) A Review of Phase Change Materials for the Thermal Management and Isothermalisation of Lithium-Ion Cells - Scientific Figure on ResearchGate. Available from: https://www.researchgate.net/figure/Verband-der-Automobilindustrie-VDA-standard-prismatic-cell-formats_tbl3_335365432 [accessed 11 Dec 2024]
(2) https://www.lslithiumbattery.com/products/ncm-102ah-1p6s-vda-module/
(3) https://www.sae.org/calendar/techsess/214605.pdf