E-Mobility Engineering 019 | In conversation: Stephen Lambert l WAE EVR l Battery case materials focus l Quality control insight l Clipper Automotive Clipper Cab digest l Optimising battery chemistries insight l Powertrain testing focus

34 May/June 2023 | E-Mobility Engineering T he range of materials for developing EV battery cases is growing, and is addressing issues of weight, assembly and even condensation. Glass fibre and composites are opening up design options frommodular systems to complete cases, while other materials are helping to improve the properties of the cases, from thermal and electrical shielding to collecting the moisture that can cause corrosion. Using plastics for a battery case can reduce the number of components required by using larger ones, which also makes the assembly process more efficient. That also opens up new design approaches for modular cases. Compared to conventional case designs using traditional materials such as aluminium and other metals, lightweight thermoplastics can potentially provide 30-50% weight savings per component, improve energy density, simplify the assembly process, improve thermal control and safety and enhance crashworthiness. This marks a major shift in automotive production but requires the entire supply chain to work together. Several large battery enclosures, moulded with using thermoplastics, are expected to be used in production vehicles as early as 2024. One plug-in hybrid EV built in China is already using a thermoplastic polypropylene compound instead of aluminium for its battery case cover, saving weight. Other EVs now in production around the world use several thermoplastic materials for components such as cell carriers and housings, battery modules and battery enclosures. This requires changes to large-component manufacturing, joining and assembly, crashworthiness, battery thermal management, flame retardancy, electrical properties and performance testing. One issue with using thermoplastics has been the structural considerations. Designers are looking increasingly at using the battery cells as part of the structure of a vehicle, which means there can be less structural pressure on the design of the case as the cells and modules take more of the stress. But that is also putting more pressure on the adhesive foams used to secure the cell modules to provide more strength as well as thermal conductivity. Flammability Flammability is of course amajor consideration for thematerial choice for a battery case, although that is already an Battery case designers have a wider than ever choice of materials for enhancing the attributes of their products, reports Nick Flaherty Housing projects Foam potting is used for prismatic cells to compensate for swelling (Courtesy of Henkel)