23rd International Colloquium Tribology - January 2022 177 Improved energy efficiency and thermal management in EVs using novel synthetic base stocks Babak Lotfi ExxonMobil Chemical Company 1. Abstract Advanced hardware designs aim to optimize performance of electric vehicles. To maximize energy efficiency, manufacturers are looking for lower viscosity lubricants. These challenges require stepout lubricant performance and novel base stock molecules. Integrated drive units, where the lubricant is also used to cool the e-motor and electrical components, bring new challenges around thermal management, electrical properties, and material compatibility. Base oil, the major component of the lubricant formulation, plays a critical role in delivering enhanced performance. Therefore, base stock properties are becoming more critical when developing superior lubricants. This research explores the use of novel PAOs in EV driveline fluids. Their balance of low viscosity and volatility, critical for the optimum performance of EV fluids, enables lubricant formulations below 3 cSt KV 100 to deliver maximum energy efficiency benefits. Novel PAOs, along with other synthetic base stocks, have been evaluated for their energy efficiency, thermal management, and electrical properties. Thermal management and cooling properties of synthetic base stocks have been studied compared to next best alternatives in an actual e-motor system. Testing suggests superior performance of synthetic base stocks which results in lower system operating temperatures. This enables increased input power and a more compact design of the system. Novel PAOs also demonstrate improved energy efficiency, which enables extended driving range. 2. Introduction Innovation is key in driving new technology opportunities. Fig. 1. depicts next generation synthetic PAOs in comparison to conventional PAOs and Gr II and Gr III base stocks. Next generation synthetic PAOs can provide an excellent balance of low viscosity and low volatility properties, which can provide an advantage for drive unit (gear-box and e-motor) performance in EV applications where new challenges like material compatibility and operating conditions pose new requirements in comparison to conventional driveline design. Novel synthetic PAOs bring new solutions and products to address increasingly challenging demands in EV as well as many other applications. Fig. 1: Viscosity vs. volatility. 178 23rd International Colloquium Tribology - January 2022 Improved energy efficiency and thermal management inEVs using novel synthetic base stocks 3. Thermal management As discussed, many automotive manufacturers have been adopting the integrated drive-unit design. In this approach, a single fluid is being used for cooling the electric-motor and electrical components, in addition to lubricating the gears, bearings and possibly clutches in the drive-unit. This can pose new challenges to the fluid development, while the compact design in the integrated system can provide more efficiency in vehicles. In this design, synthetic base stocks like PAO with desirable dielectric properties and enhanced thermal properties compared to Gr II/ III base stock can provide superior thermal management. This method can also provide a safer, lighter, and more efficient system. 4. Energy Efficiency Improving energy efficiency in both conventional and electric vehicles (including both hybrid and fully EVs) has been of high interest for automotive manufacturers. EV driveline fluids are essential in maximizing the energy efficiency in drive unit systems. Higher energy efficiency in mechanical systems, like reduction gears, can offer extended range, which is highly valuable for automotive manufactures and consumers. In this work, FZG energy efficiency FVA 345 has been used to evaluate the traction coefficient between a next-gen PAO blend and Gr II+/ III+ blend. Fig 2. shows the nextgen PAO blend has significantly lower traction than the Gr II+/ III+ blend at different lubrication regimes. Results suggest higher energy efficiency for the next-gen PAO blend compared to the Gr II+/ III+ blend, which can extend driving range in EVs. Fig. 2: FZG energy efficiency test (FVA 345), next-gen PAO blend vs. Gr II+/ III+ blend at similar viscosity (KV100) 5. Conclusion • EV design and performance targets continue to evolve and continue to bring new challenges for EV fluids • Low-viscosity low-volatility next-gen PAOs help bring new solutions to address challenging demands in EVs • Next-gen PAOs can enable enhanced thermal management and improved energy efficiency resulting in extended driving range for EVs