37 Cell-to-chassis | Tech focus with a design pattern optimised for a particular chassis design. This could mean injecting the encapsulant to flood from a single point or through multiple ports. Another approach is to pour the material over the chassis in a serpentine pattern, starting in one corner and traveling the entire length. This obviously impacts on the flow and viscosity requirements of the material. Modelling of the process can predict only approximately half of what actually happens in reality, but it can highlight those areas that are more difficult or less complicated to fill, meaning that strategies and materials can be developed accordingly. Cell supply The biggest challenge is securing a supply of cells as the design of cell geometry changes. Many suppliers provide cells in different formats, ranging from 4680, 4690 4695, and 21700 to prismatic and blade cells. The supply base for these form factors is not well established, which is one reason why the shift to C2C architecture is taking so long. Previously, the designs were protecting smaller components – the cells – in a smaller box, module, or pack. Now, C2C requires larger components in a very large box, meaning that the compression – the ability to absorb and dissipate forces – must change. The structural adhesives and encapsulants have to cope with the expansion of the cells, and some manufacturers prefer an expansion of 10 times for the encapsulant while others want half that. All of this is reflected in the latest C2C designs, which directly integrate the battery cells into the chassis, allowing for a shared structural design and the decoupling of the chassis from the upper body. Typically, the chassis is capable of absorbing 85% of the vehicle’s collision energy (compared with approximately 60% absorbed by a traditional chassis). Bedrock’s chassis has been tested with a 120 kph frontal central pole impact test without catching fire, exploding, or causing thermal runaway. This is twice the speed (56 kph) for a frontal impact safety test specified in the commonly used China New Car Assessment Programme (C-NCAP), which is the collision energy equivalent to falling from a 12 m high building. By way of comparison, a frontal impact at 120 kph is equivalent to falling from a 56 m high building. The more stringent frontal pole crash tests simulate crashes with nonstandard objects such as power E-Mobility Engineering | May/June 2025 Structural adhesives are key to cell-to-chassis designs (Image courtesy of Henkel) This could mean injecting the encapsulant to flood from a single point or through multiple ports
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