Developing lubricants and fluids for electric vehicles is a tall order – and only partly because performance requirements are more difficult than for products used in conventional automobiles, a Valvoline official told a recent industry conference.
Anant Kolekar, the company’s chief scientist and tribologist for e-drive fluid development, noted that besides developing products themselves, the industry also needs to identify performance characteristics that are important and to develop methods to measure them and equipment on which to conduct tests.
Fortunately, Kolekar told the Tribology and Lubrication for E-mobility Conference hosted Dec. 1-2 in San Antonio by the Society of Tribologists and Lubrication Engineers, the industry is making progress on all of those fronts.
“EV fluid performance requirements are more challenging than internal combustion engine vehicles and need different approaches to achieve the optimum performance,” he said.
In terms of converting fuel consumption to propulsion, EVs are more efficient that vehicles powered by internal combustion engines, Kolekar said, achieving efficiency of 80%-85% compared to 25%-36% for engines powered by gasoline and 31%-45% for those running on diesel.
In EVs, however, a greater portion of power losses are lost in the drive system – four times as much as for ICE vehicles. “So EVs need a significantly better drive system fluid,” he said.
Automatic transmission fluids and gear oils have similar performance requirements for thermal stability, foam control, cooling, electrical insulation and overall efficiency, Kolekar said. The main difference between them is that automatic transmission fluids require compatibility with yellow metals as well as superior static friction, while gear oils require superior extreme pressure protection.
EV drive system fluids require little static friction performance but greater yellow metal compatibility, electrical insulation performance, cooling ability, thermal stability and foam control than the other two products.
Kolekar said Valvoline developed an apparatus to measure electrical conductivity based on corrosion that collects on copper wires. He also cited e-transmission and EV dyno rigs developed to measure performance of EV fluids.
Using such tools, he said, Valvoline developed a drive system fluid that improved efficiency by 3%. The company also developed an ultra-low-viscosity fluid that reduced operating temperatures as measured on a dyno rig by 8.5 degrees C compared to commercially available products.
The branch of Valvoline developing such products is part of the operations that Valvoline is in the process of selling to Saudi Aramco.