A New Automotive Test Methodology – Friction Performance Assessment of Greases and Fluids for Electric Drivetrain

Electric vehicles (EV), either powered by lithium-ion batteries or by hydrogen fuel cells, represent the mainstream favored by policymakers followed by hybrid vehicles (HEV) and plugin hybrid vehicles (PHEV). The later still operate an internal combustion engine (ICE).

EV&HEV&PHEV lubricants and fluids must still keep anti-wear performances and drain intervals at a high level as well as significantly reduce friction in conjunction with compatibility to arcing and electrostatic fields when lubricating or being in contact with electric motor and reduction gears as well as fluids for cooling of inverter and battery pack.

The currently most popular e-configuration in EV&HEV&PHEV encompasses minimum one reduction gear and one differential all lubricated with one gear fluid (about 3 – 4 liters).

Electric vehicles have much different lubrication requirements than internal combustion engine vehicles, and thus a shift towards electric vehicles and electrified powertrains will demand for a new class of functionalized fluids and adopted tribometry. SRV is at the forefront in combining tribological testing with electrical contact resistance and arcing as well as is anticipating technological innovation in the direction of synthetic multifunctional lubricant and fluid formula-tions for CO2 neutral mobility.

Friction reduction in any moving mechanical system means savings in primary energy or reduced fuel consumption or longer ranges for electrical vehicles. SRV offers here tribotesting under oscillation and rolling motions, because electric and electrified powertrains use preferably rolling bearings.

Additional, hybrid (HEV) and plug-in hybrid electric vehicles (HPEV) extend the tribometric testing matrix and require more synthetic lubes, because start-stop cycles going quick to full load and heavy loads at cold start for charging or spontaneously delivering power surplus represent aggressive operation modes leading to an increased acid formation and sludge formation as well as fuel and water dilution by excessive blow-by.