Project PEAk-Bat – The development of structural battery packs

e-motec
August 31, 2023

Project PEAk-Bat – The development of structural battery packs

image of a structural EV battery pack

Farasis Cell-to-Pack Battery System © Farasis Energy

The development of structural battery packs can increase both the gravimetric and the volumetric energy density of batteries to achieve efficiency increases of up to 20 percent and enables faster time-to-market whilst reducing the number of components needed.

In addition, a structural battery pack features functions formerly realized by the vehicle chassis, such as providing stiffness and strength or absorbing crash energy. A higher integration level of cells can support the mechanical efficiency of the battery. This can be done by directly integrating cells into a pack without the use of modules, the so-called Cell-to-Pack concept which is used in structural battery systems.

Project PEAk-Bat, funded by the Federal Ministry for Economics and Climate Action, aims to research such novel approaches for the virtual validation of battery systems to reduce the number of battery tests in the development process thus reducing errors that are crucial for the subsequent production steps and to cut prototype costs.

This initiative started recently and is scheduled for 3 years. Within this period, in addition to the chair “Production Engineering of E-Mobility Components” (PEM) at RWTH Aachen University and Farasis Energy Europe, other well- known industrial companies are combining their expertise.

The project is supported by Farasis Energy Europe with the analysis and evaluation of different battery systems as well as requirements for future battery systems. The company is also responsible to analyze the manufacturing processes of structural battery systems to reduce testing efforts.

The chair “Production Engineering of E-Mobility Components” (PEM) at RWTH Aachen University provides the knowledge about different battery types and their requirements. Furthermore, it contributes its expertise of the production process of the battery cells.

Farasis Energy Europe is part of the consortium which includes Ford, Trumpf, TÜV Rheinland Automotive Component Testing, SCIO Technology and ACTS Advanced Car Technology Systems. This consortium is responsible for the project PEAk-Bat which researches innovative test methods and developments to reduce the effort for future structural battery systems.

Structural battery systems increase efficiencies and time-to-market at lower costs

“A structural battery system substitutes the basic tripartite structure with a two- tier-structure”, says Dr. Stefan Bergold, General Manager at Farasis Energy Europe. “The tripartite structure consists of cells built into modules, modules built into packs. Using the two-tier-structure, the module level can be substituted by integrating the battery cells directly into the pack housing; the so-called Cell-to- Pack approach.”

diagram image of the formation of a structural ev battery pack

Illustration of different Battery Structures

In addition to the Cell-to-Pack approach more variants of structural battery systems exist. Each one of them has their individual advantages and disadvantages. Two prominent alternatives are the Cell-to-Chassis approach and the module-to-chassis approach.

The Cell-to-Chassis approach implements the highest level of integration of the battery cells into the vehicle structure. It can be described as a one-tier structure, because there is no level in-between the battery cells and the vehicle. However, the high level of integration results in the highest requirements for the battery cells in comparison to other approaches. These requirements pose a challenge that still needs a lot of research to solve them.

Another approach which can be understood as the interim step for the Cell-to- Chassis approach is the module-to-chassis approach. The big difference between the two mentioned approaches is that the latter uses a two-tier-structure. The cells are part of modules, and these modules are integrated into the chassis.

Again, this integration poses challenges for the modules, but modules can be more easily enabled to meet the requirements. Therefore, the realization of a module-to-chassis approach can be more easily implemented, but there is still lots of research to be done.

A structural battery pack features functions formerly realized by the vehicle chassis, such as providing stiffness and strength or absorbing crash energy. A higher integration level of cells can support the mechanical efficiency of the battery.

This approach can increase overall efficiencies; both gravimetric energy density by up to 15 percent and volumetric energy density by up to 20 percent. At the same time, it reduces the number of components. This leads to a decrease in complexity, both, for the product and for the production process. The benefit from the decrease in complexity and the fewer parts results in reduced costs.

For electric vehicles, range is one of the most important factors when it comes to the buying decision of the customers. The increased energy density and the decreased weight of the whole car, due to the fewer parts, results in an increase range, making electric vehicles with structural battery packs more appealing to the customers.

A structural battery system is now to be developed within the framework of “PEAk-Bat”.

Novel approaches for virtual validation to reduce errors and costs

However, the project goes beyond this demonstrator. It aims to research novel approaches for the virtual validation of battery systems to reduce the number of battery validation tests in the development process and to cut prototype costs.

It therefore intends to establish a methodology for evaluating the need for testing when modifications are made to battery systems. On this basis, several demonstrators and test rigs of structural battery systems will be set up, test methods for cell safety will be validated and various safeguard tests will be performed.

“Early validation with the help of artificial intelligence can reduce errors that are crucial for the subsequent production steps and lower prototype costs,” says Niklas Kisseler, who is responsible for the project at the PEM Chair. “This is made possible by reducing test times, which results in faster development of new types of battery systems and thus earlier market entry,” adds PEM Chief Engineer Christian Offermanns.

Understanding the differences in international battery system requirements

To ensure safety for the passengers there are a variety of different test and norms that the electric vehicles must fulfil. Since the battery system, depending on the used cell chemistry can possibly pose a threat to customer safety there are a set of norms and tests dedicated to the battery system.

Because of the continuously fast development pace of battery systems, the norms need to be updated on a regular basis. Therefore, when developing a battery system, the most recent norm must be researched and applied.

image showing the different engineering standards for EV battery packs around the world

Overview of the different national standards for battery testing

Another effect of the fast development pace of battery systems is the missing international standard for norms and tests. Each country or economic zone like the EU have their own set of norms, sometimes with big differences in certain aspects. Although there have been and still are attempts to further the standardization process, it is still a long way to go. One reason for the missing standardization is the different scopes of the economic zones. For example, China has a stricter requirement when it comes to thermal propagation of the battery packs than the other economic zones, which started to adapt the Chinese standard.

These international differences are researched and structured in the framework of “PEAk-Bat”. The resulting requirements are then integrated into the development process of the structural battery system.

Researching future battery system requirements and analysing manufacturing processes

“Farasis Energy Europe is involved in two working areas to support this initiative”, states André Gronke, Head of Overseas Product Development of the company. “Following a holistic Systems Engineering approach, analysing the requirements of future battery systems both from a customer and regulation perspective is an important first step. On top we support the evaluation of different concept approaches with our broad experience from global automotive and non- automotive customer projects. Secondly, we’re involved in the manufacturing process analysis and optimization for structural battery systems.”

He continues: “Together with the project partners, we develop evaluation criteria for the assessment of battery systems based on different applications, e.g., manufacturability, integration, re-use/ repair capability, supply chain aspects, logistics and costs. Here, we benefit from the diversity of the project partners, representing big companies and start-ups, including an OEM, a toolmaker, an institute for accreditation of processes, testing and certification as well as a cell and battery manufacturer.”

Farasis contributes its experience and expertise in global trends and evaluates the concept of design space derivatives in relation to overall system integration.

Another involvement is the production analysis of structural battery systems. Farasis evaluates process dependencies for the producibility of structural battery systems (cell and system), investigates different state-of-the-art and future construction methods of battery systems and their potential. Also related to battery manufacturing is the necessity of testing during the production process, both for characterization purposes and to avoid that a product violating the aligned specification can reach the customer’s factory. Reducing and simplifying the efforts will optimize production time, factory space requirements and overall costs.

Initiatives like PEAk-Bat are becoming more important to achieve global CO2 emission targets and enable energy storage systems like batteries to become an alternative to fossil fuels, which are becoming scarce. “In the transport sector,

electrified vehicles are becoming more popular as a means of reducing the carbon footprint”, states Bergold. “One of the biggest challenges of electromobility are higher costs compared to conventionally powered vehicles and the PEAk-Bat initiative could be one asset to reduce costs whilst increasing efficiencies. We are proud to contribute to this initiative with our expertise as a leading developer and producer of high performance lithium-ion battery technology and pouch cells for electric mobility and other energy storage applications.”

About Farasis Energy

Farasis Energy is a developer and producer of high-performance lithium-ion battery technology and pouch cells for electric mobility and other power storage applications. Founded in California in 2002, the company now operates research and development centres in China, Germany, and the USA. There are currently two production facilities in Ganzhou and Zhenjiang (China), further production facilities are currently under construction in Wuhu and AnNing (both in China). A fifth production facility is under construction as a joint venture, Siro Energy, with Togg in Gemlik, Turkey. Besides Togg, Farasis Energy’s major strategic partners also include companies such as Daimler and Geely.

About the Chair “Production Engineering of E-Mobility Components” (PEM) at RWTH Aachen University

The activities of the chair “Production Engineering of E-Mobility Components” (PEM) revolve around Electric Mobility. The core activities are teaching, researching and consulting of various topics of the E-Mobility and its components. These competences have been built over the years with various research and industry cooperations with a variety of different cooperations.

Press contact

Farasis Energy Europe

Ilona Arnold

+49 (0)7022 789 4484

press@farasis.com

Chair of Production Engineering of E-Mobility Components (PEM)

Niklas Kisseler

n.kisseler@pem.rwth-aachen.de

+49 (0) 1511 5647419

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