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

are so many thermal interface products available,” he says. One important aspect of optimising heat transfer is maximising the effective contact area between the heat transfer material and the component, the fluids specialist argues. “Dielectric thermal management fluids offer advantages in this respect, because the entire system can be immersed in an effective heat transfer fluid,” he says. “There is also much less need for thermal transfer materials, because the hot surfaces are in direct contact with the fluid. That means more heat can be removed from a greater surface area compared to an indirectly cooled system.” High-voltage ancillaries A further trend in EV thermal management systems is the move to powering components such as coolant pumps and heat exchanger fans from the high-voltage supply, which has implications for the system as a whole. Powering any component from the high-voltage supply makes it more efficient because of the reduction in ohmic losses resulting from the reduction in current for any given power level, the fluids specialist points out. Being more efficient, he adds, the pumps and fans can deliver more cooling power. “Ultimately, EV manufacturers will implement a thermal management system that meets the cooling and heating requirements of the vehicle at the right cost,” he says. “Using more of the pack energy to cover more miles and less to power auxiliary components will be a differentiating factor.” Being able to run the cooling peripherals at higher power will certainly have a significant and positive impact on cooling system efficiency, the first materials specialist notes. With EV designers targeting high charging rates – a full charge in 10 minutes in 800 V systems, for example – optimising the power of the cooling system will help to operate cells at lower and more uniform temperatures, increasing the system’s robustness and reliability. Developing the next generation of systems is focused on eliminating energy consumption from components that are not in use, the automotive powertrain specialist notes. “For example, eliminating the energy use from valves and sensors can help to increase the energy efficiency of the entire system,” he says. Polymer e ects The use of polymers in battery module and pack structures will have an impact on thermal management systems. The main driver here is a reduction in the overall mass of the pack without sacrificing structural integrity, but it also allows for the integration of additional functions by moulding facilities for them directly into modules. Coolant paths are prime candidates for this, the automotive powertrain specialist says. The fluids expert stresses the importance of co-engineering when addressing the designs and materials for direct thermal management of battery systems containing structural polymeric material. “For immersive thermal management systems, the materials and functional tests should be carried out very early on in the design pathway to ensure compatibility with the fluid and to maintain system safety,” he says. If not specifically engineered for thermal conductivity, the first materials specialist says, polymer cases will need smart heat path solutions to achieve the required heat transfer rates. “The design key is to make sure the system – no matter where the hotspots are – has a way to transport heat, which with thermal isolators such as plastics is a challenge,” he says. The fluids specialist recently launched a new dielectric coolant for directly cooling batteries, power electronics and motors as part of a range of fluids for EVs that also includes e-transmission fluids and e-greases. Independent tests show that the fluid performs better than water-glycol indirect coolants and other dielectric coolants in EV lithium-ion batteries, company literature says. Compared with a water-glycol-based coolant, for example, the new fluid enabled 41% faster charging, meaning 10 minutes to 80% charge compared with 14.1 minutes for water-glycol fluids for the same type of cells. During discharge, it has been shown to lower peak cell temperatures by 28 ºC and to reduce variations in cell temperatures by 8 ºC compared with water-glycol fluids. Compared with other dielectric fluids, it reduced peak cell temperatures by 11 ºC and variation between cells by 2 ºC. The equivalent figures demonstrated during charging are C17 and C2 compared with water-glycol, and C11 and C3 compared with other dielectric fluids. These improvements enabled higher performance at a given maximum temperature, the company says. Thermal management is a key enabling technology for e-mobility, and the pace of its evolution dictates that of the whole industry to a great extent. Focus | Thermal management Acknowledgements The author would like to thank Dr Marc Payne at Castrol BP, David Nash at Dana, Holger Schuh at Henkel, Dr Roger Busch at Mahle, Eric Dean and Dr Anurodh Tripathi at Parker Lord, Lewis Evans and Christian Marks at Senior Flexonics, and John Williams at Aspen Aerogels for their help with researching this article. Cooling plate design is an important contributor to minimising any temperature differences between cells in a battery pack (Courtesy of Senior Flexonics) 72 January/February 2023 | E-Mobility Engineering