Electric Axle Offers Fuel Savings for Long-Haul Operations

February 2018, - Feature

by Deborah Lockridge, Editor-in-Chief - Also by this author

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Mesilla Valley Transportation, PAM Transport, and Ryder conducted initial road testing on Hyliion’s 6X4HE hybrid-electric axle. Photo: Hyliion
Mesilla Valley Transportation, PAM Transport, and Ryder conducted initial road testing on Hyliion’s 6X4HE hybrid-electric axle. Photo: Hyliion

A start-up company has launched production of an add-on hybrid axle system designed to save fuel in long-haul Class 8 trucks.

Hyliion says its 6X4HE hybrid-electric axle system technology can deliver fuel savings, lower emissions, instant telematics and a better driver experience.

The company, which initially launched designing a hybrid axle product for trailers, showcased the new tractor axle at last fall’s American Trucking Associations’ Management Conference & Exhibition. At that point it was just coming off of initial testing on trucks run by Mesilla Valley Transportation, PAM Transport, and Ryder. Since then Hyliion has been working on fine-tuning the system, but it is already available for order.

“Hyliion is bringing hybrid technology to the Class 8 trucking market, but we’re doing it in a very unique way,” explained CEO Thomas Healy in an interview. “You keep the existing diesel-engine truck that you own, and we add a hybrid electric assist to it to help reduce the amount of fuel you consume.”

When the truck goes downhill or applies the brake or Jake Brake, the system uses regenerative braking to help capture some of the wasted energy and stores it in a battery pack mounted between the frame rails behind the cab.

“When you go to climb a hill or accelerate, we can take that electric energy we have stored and apply it to our electric motor, which then applies torque and helps reduce the amount of fuel the vehicle uses,” Healy said.

Hyliion’s 6X4HE system replaces a 6x2 truck’s non-driven dead axle or is added to a 4x2 truck, turning either into a 6x4. Existing 6x4 tractors can be converted by removing one mechanically driven axle and replacing it with a Hyliion axle. The system includes a motorized axle, lithium-ion battery pack, and electronic controls. It adds about 800 pounds to the weight of the truck.

PAM’s test unit was installed on a new Peterbilt 4x2 tractor, while MVT and Ryder converted in-service International and Freightliner 6x2 tractors, respectively. Systems operate autonomously with no driver involvement.

The axle’s hybrid action alone will save 15% in fuel, the company says, predicting fleets could see up to a total 30% fuel savings using the battery pack to run an auxiliary power unit during rest periods.

“The system has a separate warranty that does not affect the manufacturer’s warranty,” Healy said. “We are offering a three-year warranty and the ability to extend it for another two years. Our warranty will cover the Hyliion components and will not affect the OEM/truck components.”

The Hyliion system includes a motorized axle, lithium-ion battery pack, and electronic controls. Photo: Evan Lockridge
The Hyliion system includes a motorized axle, lithium-ion battery pack, and electronic controls. Photo: Evan Lockridge

On the road

Initial fleet testing focused on driveability and system integration. Ron Knowles with Mesilla Valley Transportation has been in charge of the Hyliion project at the Texas-based company, a fleet known for its innovation in fuel efficiency.

“At first I didn’t know what to expect when I picked it up,” he told HDT. “I was expecting more of a kick like a Tesla car. It’s a really gradual, easy transition. Sometimes you don’t even think it’s actually powering, but at times you do, and you get out of the throttle and can feel it propelling you up the hill. When you’re coming off the hill it goes into regenerative energy and starts collecting the energy back into the batteries, so it almost acts like an engine brake.”

Kim Kasee, vice president of marketing for Hyliion, told HDT in a follow-up interview in late December that driver comments in testing so far praised the smooth ride. “It felt like they were hauling a half load instead of a full load,” she said.

Paul Pettit, vice president of maintenance for Arkansas-based PAM Transport, said the Hyliion technology could potentially be a game-changer.

“I think the fuel savings is the thing everybody’s chasing in the industry,” he said. “I think having this technology to be able to potentially save 30% on your fuel economy is second to none, and it’s an innovation that has not been done before.”

However, when asked about the fuel economy, Knowles and Pettit both said testing thus far has not really focused on the efficiency numbers.

Pettit told HDT early last month that PAM was scheduled to receive an updated production version of the system on its truck mid-month. “I think we’ll be a little closer to what is anticipated for the fuel savings,” he said. “We weren’t really close as far as fuel savings proposed numbers with the [pre-production] test unit, because they were working out the kinks and making sure all the hardware was up to speed and ready to be used.

“We’re excited to really put it through its paces and see how it’s going to be best used in our fleets and what kind of numbers we can get utilizing it with our freight.”

It adds about 800 pounds to the weight of the truck. Photo: Evan Lockridge
It adds about 800 pounds to the weight of the truck. Photo: Evan Lockridge

The brains of the system

Key to the performance of the Hyliion system is its computer brain. Kasee explained that the Hyliion controls are a “passive listener” on the vehicle’s CANBUS. “So we can see what they’re doing, but we don’t undo what they’re doing. “

The Hyliion 6X4HE, Kasee explained, looks at how much energy it has stored, and at the topology of the road in front of it, and determines how to take that energy and apply it for the best fuel savings.

“If you have a road that’s up and down and up and down with smaller inclinations and declinations, then it’s pretty simple how we drive the energy into the motor and create energy on the downhill side to replenish that. If it’s a steeper hill, like a mountain, it applies it a little bit differently to try to keep that engine in the sweet spot.”

In fact, she said, on some steep inclines the system may not stay on during the entire incline. In order to be able to power up long mountainous grades, it would have required a larger battery that would reduce the available cargo payload too much. “So it’s more of an assist than a pure power play.”

Those electronic controls are still being fine-tuned. “As with any algorithm-based product, the more data you have, the more performance you can eke out of the hardware. So what’s really critical to us is that we keep growing that database so we can keep tuning how the system reacts to elevation changes and to what the tractors are doing.”

Hyliion is running further tests with the updated production units on the first three trucks, and more fleets are going to participate, she said. In addition, Hyliion is putting the system on three new Peterbilt trucks it has purchased. It will lend them to fleets to try in their operations without having to retrofit one of their own trucks.

Pronounced HIGH-lee-on, Hyliion is a true start-up company, less than three years old, the brainchild of some mechanical engineers who wondered why there were hybrid cars but not hybrid big rigs. They weren’t from the trucking industry, but have drawn heavily on the expertise of fleets near the company’s Pennsylvania headquarters. Healy sees being an outsider as an advantage rather than a drawback: “Since we all come from different backgrounds, we bring technology used in other industries to the trucking industry in a very unique way.”


  1. 1. Jerry_54 [ January 16, 2018 @ 11:31AM ]

    This is the kind of tech we need today! Not this 100% electric stuff that requires we buy new rigs and wait for charging stations to pop up along our routes. This is the first truly exciting development in the field that I've heard of.

  2. 2. KJMeekins [ January 19, 2018 @ 06:06AM ]

    Similarities in applicability to natural gas fumigator system where passive power assist is offered without altering vehicle design. Like the fumigator system this unit could conceivably be swapped out for use in another truck at trade in.

  3. 3. Steve [ February 26, 2018 @ 06:19AM ]

    why not just swap out your driveline carrier bearing for an electric motor.
    ( this would be accepted by a much larger pool of potential truckers )


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