Electric Vehicles may not be commonplace in waste fleets just yet, but fleet managers should be prepared for this change and keep abreast of ongoing technological advancements.
By Darryl Purificati
The introduction of electric vehicles (EV) has begun and many industries, waste management included, are starting to see the impact. While traditional, internal combustion engine (ICE) vehicles remain by far the most common, the rise of EVs is set to continue.
As part of this change for waste fleets, fluid and lubricants are essential to capacity and efficiency. We are driving innovation in this space by working with EV Original Equipment Manufacturers (OEMs) to help them develop the next generation of technologies that will power waste fleets in the future.
Waste fleet owners and operators must be prepared for the coming transition be and familiar with the technologies they will have to work with every day. Following are key questions about EV lubricants we are seeing across the industry, and the answers that are shaping future technologies.
Efficiency in a Driveline Unit is Vital When it Comes to EVs, How Can Lubricants Contribute to Maintaining it?
There are various ways to improve the efficiency in the driveline unit and therefore key factors to consider when selecting lubricants.
A unique challenge to EVs is that heat must be removed from the motor as quickly as possible to improve its performance and overall system efficiency. This means that EV lubricants must have exceptional heat transfer characteristics. The fluid’s viscosity is a major enabler of improved fluid thermal management; EV lubricants have typically lower viscosity than conventional automatic transmission lubricants.
How Can EV Driveline Lubricants Offer the Right Level of Protection?
Electric motors run at high revolutions per minute (RPMs), meaning the driveline lubricants need to work hard to protect gears from wear damage. Waste fleets are subject to strenuous operating conditions, working long hours, seven days a week, often with stop-starts and idling, which makes gear protection incredibly important.
It is a challenge to combine sufficient protection with the high performance expected in the next generation of vehicles. Success means the lubricants will reliably transfer power to the wheelbase with minimum drag and churning in the gear set—all the while providing the protection that is required to keep the asset working for longer.
Driveline lubricants for EVs are typically low-viscosity lubricants, providing better flow throughout the electric motor and parts. The appropriate fluid can help reduce friction on the gears and bearings while allowing improved heat transfer and thermal efficiency. Combined, the motor will be able to run at its highest efficiency, keeping copper windings and motor components within optimal electrical motor efficiency.
Is Material Compatibility and Conductivity a Factor When Choosing an EV Lubricant?
Yes, material compatibility is essential with EVs due to the copper hairpin windings and electronic components. Unsurprisingly, EV fluid’s electrical properties are a key factor. Whereas an ICE-based driveline fluid, used by most waste fleets today, is primarily focused on durability and performance, for EV lubricants, it is critical to include a balance of conductivity, while avoiding issues with electrical arcing or sudden electrical discharge.
The hardware of an EV is fundamentally different to an ICE and in many cases the motor is in the same compartment as the gearbox. As there is an electrical current going through more components, OEMs must work collaboratively with EV fluid developers to design lubricants to their optimum conductivity—the aim is to keep it low but avoid electrical discharge and damage to the electric drive unit.
Of course, it is crucial to maintain adequate wear protection. This is particularly true for waste vehicles that are carrying high loads for long periods under significant demand. A quality EV fluid will protect the e-driveline unit by providing adequate protection, electrical properties and compatibility with copper and new materials while improving the unit’s efficiency.
How Essential is Thermal Management to Cooling EV Lubricants?
Thermal management lubricants are crucial to EVs and require a careful balance between thermal insulating quality, and electrical non-conductivity to prevent the build-up of electrostatic charges.
There are two types of fluid technologies for cooling in EVs—direct and indirect. Most major manufacturers have, to date, used indirect cooling, meaning various surfaces and plates are cooled by a cooling fluid, which then cools battery cells. This method does have some safety concerns, primarily, if there is a fire in one cell, it can spread to other cells and cause an explosion.
Comparably, direct cooling, or immersion cooling, while not directly used yet in many EVs, involves dielectric lubricants that help dissipate the heat from the battery and can reduce the chance of thermal runaway or explosion. Similar to transformer oils, both need to be non-conductive, however, differences emerge when it comes to material compatibility, safety, and performance.
Currently, the go-to fluid type is a water-glycol mixture. Unfortunately, they are relatively conductive and cannot be used in direct contact with a battery. We would expect to see the industry change to mineral oil-based immersion cooling lubricants in the very near future.
What am I Now Looking for in an EV-Bearing Grease?
The high operating speeds and materials compatibility requirements of the electric motors in the EVs that will typically be used by waste fleets require specialized greases. Greases designed for these provide extended high-speed bearing life through enhanced oxidative and thermal stability. They also use carefully selected base lubricants, thickeners and additive systems to provide both low friction to extend driving range and low noise operation. In addition, the additive systems must avoid the use of corrosive extreme pressure (EP) additives that can damage the copper motor windings. A final consideration is electrical conductivity. EV greases need optimized conductivity to protect bearings from damage due to electrical discharge.
The unique aspects of EVs impact grease choices in other areas as well. EVs are typically significantly heavier than their ICE counterparts due to their batteries. This added weight means extra stress on driveline components such as the constant-velocity (CV) joints. EVs bring an opportunity for more specialized CV joint greases that have higher EP protection than in a traditional vehicle.
Staying Ahead
EVs may not be commonplace in waste fleets just yet, but fleet managers should be prepared for this change and keep abreast of ongoing technological advancements, such as we are seeing in EV lubricants. | WA
Darryl Purificati is Sr. Technical Advisor, OEM/Automotive at Petro-Canada Lubricants, an HF Sinclair brand, and Chair of the American Petroleum Institute (API) lubricants committee. For more information about Petro-Canada Lubricants EVR, its first line of purpose-built lubricant solutions for EVs, visit power4evr.com.