38 poles, large trees, or animals. Here, the impact area is only 1/6 th of that in a full-width frontal impact, exponentially increasing the impact pressure. At a speed of 120 kph, the impact pressure on the chassis per unit area in a frontal central pole impact is 21 times that of the C-NCAP 56 kph full-width frontal impact test. Similar to the shell of a tortoise, the chassis comprises a three-dimensional structure in which the body and battery framework are integrated. Arresting structures disperse impact forces across multiple pathways during a crash, gradually decelerating the vehicle and significantly reducing the depth and speed at which obstacles intrude into the cabin. The chassis uses submarinegrade hot-formed steel with strength of 2000 MPa, aerospace-grade aluminium alloy with strength of 600 MPa and multiple barrier structures to further boost chassis rigidity. The NP Technology’s battery cell design and high-ductility energyabsorbing insulation film currently represent industry-leading technologies in terms of battery safety and stability. The high-voltage disconnection architecture achieves disconnection within 10 ms of impact and completes the discharge of residual high-voltage energy in the vehicle within 0.2 s. The battery cells have undergone highly demanding tests, including highspeed sled impact tests at 60 kph, 90° bending tests and breakthrough sawing tests, and the battery did not catch fire or explode across all three tests. This chassis can be used for multiple e-mobility vehicle models, thereby shortening the r&d cycle. This reduces the time required for mass production from the traditional 36 months or longer to just 12–18 months. Assembly Some requirements are for adhesive curing time that is as rapid as possible, but there are also battery parts that must be pre-glued in one location and then cured in another location depending on customerspecific logistics. To keep the cells together, assembly adhesives are used in addition to the structural adhesives and the encapsulants. Safety remains a topic of innovation because the energy density is changing in association with the development of C2C battery systems. For example, in terms of coatings, the previous two years have seen designs moving from modules to C2P, and the requirements on battery safety coatings have become increasingly strict. This has required the development of new heatshielding materials. With the change from C2P to C2C, the requirements demanded of certain parts are changing. With cells integrated into the chassis, the structural adhesives must be redesigned to provide greater structural stability, while the encapsulation material is needed to offer protection. The adhesives need to deal with all the vibrations that are transferred directly from the chassis but with greater elasticity, and also provide greater durability against ageing; achieving a material with this combination of features is a major challenge. There are other cooling concepts that come with C2C designs that affect the requirements for the adhesives and encapsulant. For example, with immersion cooling, the cooling snakes that fit between the cells must have the characteristics of structural strength and corrosion resistivity. If there is a cooling plate between the cells, then a thermal gap filler or thermally conductive adhesive is needed. There is also more space within the chassis to be filled by cells. Normally, structural adhesives are applied from the cell to the substrate, with assembly adhesives used between cells to provide flexibility. For example, given a row of 30 cells, there must be a certain degree of flexibility to avoid them being too stiff, which requires a balance between the semi-structural and structural adhesives. CTM assembly has moved to adopt thermally conductive adhesives starting at a thermal conductivity of 3 W/m K; however, the gap is smaller for C2P, so thermal conductivity of 1.5–2.0 W/m K is sufficient. A C2C design requires excellent thermal regulation by the thermal interface materials and heat shielding because the chassis can be exposed to the cells. Therefore, heat shielding is installed on the top of the cells. In terms of managing thermal propagation, several solutions are available for keeping a fire in one Tech focus | Cell-to-chassis May/June 2025 | E-Mobility Engineering Design of the Bedrock chassis to address impact safety (Image courtesy CATL)
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