E-Mobility Engineering 017 l ECE Doosan electric excavators dossier l In Conversation: Matt Faulks l Battery testing focus l Battery Show North America 2022 report l Ariel Hipercar digest l Cathode materials insight l Thermal management focus

The material comes from the manufacturer as a blanket capable of withstanding temperatures up to 1400 ºC and of preventing C2C conduction of heat with blankets as thin as 2 mm. Integrated functions Innovations in battery design, particularly the integration of electrical, thermal and structural functions into enclosure components to improve pack-level energy density, will also affect thermal management. The automotive powertrain specialist regards that as a trend worth monitoring, arguing that multi-function components can reduce parts counts and simplify battery pack manufacturing processes. “That leads to different solutions depending on the requirements, ranging from immersion-cooled battery systems to cooling structures integrated into the battery housing,” he says. The fluids specialist, for example, favours this approach, arguing that immersion cooling using a dielectric fluid enables optimised pack designs. “For example, busbars can get quite hot during high-power charging. If these can be cooled by the dielectric fluid then they can be made smaller so less material is used, saving weight and cost,” he says. “Getting rid of dedicated cooling loops by bringing the electronics closer to the pack will improve energy density, but care should be taken with the dissimilar temperature limits between cells and power components. Direct cooling of electronics can boost the pack energy density even further, as the electronics can be downsized.” The company is a partner in the UK’s APC18-funded Celeritas programme, which addresses this concept, he adds, with the aim of producing battery packs for hydrogen fuel cell hybrid vehicles as well as for full battery EVs. The vehicle electrification specialist says the battery enclosure is a promising target for reducing the complexity in EVs. The company is developing a composite battery case that promises a reduction in weight of up to 30% compared with a metal equivalent, and integrates the cooling path routing and cold plate, sealing, and heat shield functions. One major challenge in this area will come from reducing the number of load- bearing structural components inside a battery pack. The thermal interface materials and adhesives specialist argues that while having fewer module parts will free up more space for cells in the battery, it will also create a need for more and better bonding materials. He stresses that these materials will have to be multi-functional, have long service lives, high bonding strength and solid thermal performance. They will also have to withstand the stresses placed on the structure during operation, withstand impact loads and be de-bondable for repairs. The company has a team dedicated to developing such materials. “Early engagement in concept and design discussions is even more important here, because the battery pack will be relevant to the vehicle’s crash performance, and therefore so will the thermal management materials and components,” he adds. Cooling power electronics High-performance power electronics present challenges that require new thermal management approaches. Both our materials experts emphasise that the needs of inverters, DC-DC converters and onboard chargers are as important as those of other major components in the powertrain, and that this reinforces the case for involving them early on to optimise the operation of the vehicle as a whole. Critical issues for early discussion include thermal conductivity, viscosity and compatibility with electrical components. Early involvement improves understanding the overall system design concept, while providing more time to evaluate the wide variety of products and matching them to critical needs such as high-voltage isolation, tolerance of harsh operating conditions and high temperatures. “In our view, the best strategy would be direct cooling with dielectric single- phase fluids in a spray or impingement system,” the fluid specialist says. “That is because these cooling methods allow significant reduction of thermal resistance and a lower pumping power demand, and they can be integrated with other EV drivetrain subsystems such as the traction motor, e-drive and geartrain.” Another approach to cooling power electronics is the use of an internal diverter plate, the electrification specialist says. This can produce uniform temperatures across all the power modules in an inverter, for example, reducing the risk of excessive temperatures in chips. “With the increased interest in the use of new wide-bandgap semiconductor Moving heat around and between components in an EV’s powertrain using heat pumps, refrigerant loops and heat exchangers is essential in the drive for energy efficiency (Courtesy of Mahle) January/February 2023 | E-Mobility Engineering 67 Focus | Thermal management