Lube-Tech
Drivetrain fluids for electrified vehicles (EVs), both hybrid and full electric, have differing requirements from conventional fluids. Traditional performance needs such as oxidation protection, material compatibility, aeration resistance, and wear protection are still important, but new challenges exist in the form of electrical conductivity, heat transfer, high speed durability, compatibility with new and different materials, and battery cooling. Conversely, friction performance – critical to applications employing wet clutches - is now of lesser importance as the range of system operating speeds is now covered by variable speed motors, rather than conventional step gear transmissions. Adding to the complexity of the electrified drivetrain space are the myriad hardware configurations as each drive unit manufacturer seeks their own solution to transmit power to the wheels. There are no “one size fits all” solutions.
While many existing systems employ automatic transmission fluids in their electrified drivetrains, these fluids may not be optimal for each solution, as they were designed around the needs of more conventional applications. In order to improve fluid performance in electrified vehicles, it is vitally important that formulators designing these fluids have tests at their disposal that properly correlate to real world systems.
24 LUBE MAGAZINE NO.170 AUGUST 2022
PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
No.141 page 1
Test methods for evaluating electrified vehicle fluids
Matt Jackson, Director, Fuels and Driveline Lubricants Research, Southwest Research Institute (SWRI)
Suitable tests for conventional fluids have been developed and improved over decades. These controlled test methods are used to assess fluid performance and allow the evaluation of formulation changes against known standards. Unfortunately, similar tests for electrified vehicles simply do not exist, or are at best in early stages of development.
There are industry efforts underway to adequately identify the performance needs of EV fluids and develop tests to evaluate them. SAE International has authored “Information Report J3200 on Electric Drivetrain Fluids (EDF)” as a guide to understanding the terms related to EV fluid properties and existing tests that may have applicability to EV fluid evaluation. Southwest Research Institute’s Advanced Fluids for Electrified Vehicles (AFEV) Consortium is a joint industry project whereby member companies pool resources to explore precompetitive concepts to properly characterise EV fluids.
Ultimately, new tests will need to be developed that address the specific needs of EV fluids. These new tests will need to assess performance with respect to electrical and thermal properties, compatibility with materials unique to EV systems, high speed durability, oxidation and aeration resistance, and battery performance.
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