Today's Trucking
products Engines/Drivetrains Trucks

Hybrids are Coming

Posted: August 1, 2014 by Rolf Lockwood

Financially difficult yet somehow compelling anyway, the hybrid truck is on its way. What remains to be done is what manufacturers call ‘commercialization’ — the process by which a new technology reaches a stage of critical mass such that it’s affordable to the many instead of the rich and adventuresome few. With the exceptions of FedEx and UPS, so far it’s only a few public bus and utility fleets backed by government purses that have actively explored hybrid alternatives.

That will change, probably, but it’s clear — in North America and Europe alike — that incentives of some useful size are required very soon if we’re to move ahead.

In our last Online Weekly Feature (Hybrids, Hybrids Everywhere — link at bottom of page), we looked at hybrid motive power in a general way and especially at the demands of the utility-fleet customer. The focus was on the diesel/electric combination. This time we’ll look at what Eaton and some others have been doing, including some very interesting diesel/hydraulic options.

I’ll have to save developments in battery technology for another issue in the next month or two.


Last year, a diesel-electric hybrid utility pilot program was launched in the U.S., focusing on 24 International medium-duty utility trucks with an Eaton diesel/electric powertrain.

Eaton, which appears to have a solid position at the head of the hybrid convoy, has also been working with the likes of Freightliner and Peterbilt on the heavy side, and especially with FedEx and UPS in making urban delivery trucks. In November, Eaton was awarded several U.S. patents for its hybrid electric power system, which will be formally available through several major OEMs next year. The patents are focused on controls and systems, but of particular interest to many fleets is the patented ePTO (power take-off) feature. In applications where a truck operates in an off-highway job site, such as utility and telecom applications, the Eaton ePTO feature provides the ability to run equipment while the engine is off — resulting in fuel savings of up to 60 percent and engine idle time reductions up to 87 percent.

As with other such systems, broadly, there’s an electric motor/generator located between the output of an automated clutch and input of the Fuller automated transmission. The system recovers energy normally lost during braking and stores it in lithium ion batteries. When electric torque is blended with engine torque, the stored energy is used to improve fuel economy and vehicle performance for a given speed, or it can operate with electric power only.

Last June Eaton announced it has begun development of a hybrid electric power system for heavy-duty trucks, and not just local refuse packers but on-highway machines. The class-8 system will be similar in design and will share many of the same components as the medium-duty equivalent. Eaton says fleets will see significantly reduced fuel consumption, adding that independent test results have shown a 5-7-percent saving versus a conventional class-8 vehicle while driving, and a saving of one gallon per hour when parked.

The system’s batteries power the heating, air conditioning, and truck electrical systems while the engine is off. When the idle-reduction mode is active, engine operation is limited to battery charging, an automatically controlled process that will take about five minutes per hour. In the proposed design, a proprietary feature minimizes engine vibration during start-up and shut-down during the recharge periods, allowing the driver to rest without interruption.

“We see an exciting future for hybrid electric vehicles in the heavy-duty market place,” says Kevin Beaty, manager of Eaton Hybrid Power Systems. He adds that the system is in the testing and development phases, and they’re working with truck and engine makers and select fleets to produce prototypes for field evaluation. The system is expected to be available well before 2010, and could help meet that year’s EPA emissions regulations.

Eaton is not the only player in this game on our side of the Atlantic, though its lead is substantial. Arch rival Arvin­Meritor is about to enter the fray as well. In a chat with chairman Chip McClure and the new president of Commercial Vehicle Systems, Carsten Reinhardt, at the recent IAA show in Hannover, Germany, I learned that the company has delivered a chassis with hybrid powertrain to Ontario body-builder Unicell. The project was announced late last year and it’s making headway, with the ball now in Unicell’s court.

The Eaton Hydraulic Launch Assist system works as
a secondary energy source during peak power demand

Also at Hannover, Volvo displayed a hybrid powertrain for heavy vehicles, combining a D7 diesel engine with electric power for stop-and-go city operations. Volvo says it will be possible to launch hybrid trucks on the market “within a few years.”

Mitsubishi Fuso is perhaps further down this road than almost anyone else. Now firmly part of the DaimlerChrysler empire, it showed its ready-for-market Canter Eco-Hybrid truck at two U.S. shows earlier this year and more recently in Hannover. It’s almost certain that we’ll see the diesel/electric class-4 truck here within a couple of years, possibly even in the Sterling 360, a badge-engineered version of the Canter. It’s for sale now in Japan. It combines a small, clean-burning diesel engine, an ultra-slim electric motor/generator, and advanced lithium-ion batteries in a drivetrain that also includes an ­automated mechanical transmission.

“We at Fuso really believe in hybrid power,” company president and CEO Harald Boelstler told me at the IAA show. “But our aim is that this technology must make a business case in the medium and long term.”


Then there’s Eaton’s joint venture to produce a hydraulic/diesel hybrid urban delivery truck for UPS in concert with the EPA, International Truck & Engine, and the U.S. Army. In lab tests the technology has achieved a 60-to-70-percent improvement in fuel economy and more than a 40-percent reduction in carbon dioxide emissions, compared to a conventional UPS vehicle. It’s being tested on the streets of Detroit now.

A high-efficiency diesel engine is combined with a unique hydraulic propulsion system, replacing the conventional drivetrain and transmission. The vehicle uses hydraulic pumps and hydraulic storage tanks to store energy, similar to what is done with electric motors and batteries in hybrid electric vehicles.

Fuel economy is increased in three ways: vehicle braking energy is recovered that normally is wasted; the engine is operated more efficiently; and the engine can be shut off when stopped or decelerating.

“Eaton sees the series hydraulic hybrid as a natural and exciting progression in the development of hydraulic hybrid systems,” says Craig Arnold, Eaton’s senior vice president and president of the Fluid Power Division.

Similar but simpler technology, which will be available as early as 2007, will find its way into some class-8 vehicles too. It’s been installed in a Peterbilt Model 320 LCF garbage truck, among others, and is presently being tested on the road. Called Hydraulic Launch Assist (HLA), it’s a parallel system in which a gas or diesel engine with conventional transmission and drivetrain is boosted by stored hydraulic power through a reversible hydraulic pump/motor that sends serious additional torque directly to the driveshaft. The system can provide high torque very quickly, even at very low speeds — like 1,000 lb ft at 0 rpm.

HLA works by recovering a portion of the energy normally lost as heat by the vehicle’s brakes, in the form of pressurized hydraulic fluid. This fluid is stored in on-board accumulators until the driver next accelerates the vehicle, at which point the hydraulic pump becomes a motor.

HLA is designed to provide maximum benefit for vehicles with 7,000 lb or higher GVW and engaged primarily in stop-and-go work. It’s been in development for ­several years and is currently in its third generation.

Among the trials is a truck built for the U.S. Army. In that case, Eaton says the HLA system can provide a 25-to-35-percent improvement in fuel efficiency, with 25-to-35-percent reductions in emissions, and even greater reductions in brake wear.

Ford has also been working with Eaton on HLA and has had the system in a heavy F350 pickup truck for a few years now. It’s pretty high on this technology.

“Ford thinks that both electric and hydraulic regenerative systems have a future,” says John Brevick, a Ford mechanical engineer working on the HLA system. “But for heavy vehicles like our 10,000-lb F-350 trucks, hydraulics are better at capturing lost energy than electric systems.”

With as much energy as the system captures and then reproduces, a 10,000-lb vehicle can accelerate from a dead stop to between 25 and 30 miles per hour with no assistance from the vehicle’s combustion engine.

While it’s impossible to get anyone to comment on price, it seems logical that hydraulic hybrid options could well be cheaper than electric and more appropriate in some applications. The controls are certainly simpler on the face of it. And maintenance would be a decidedly less complicated task. Sounds promising.

We’ll explore more of the future in the coming months.


  • This field is for validation purposes and should be left unchanged.
Related Links & Documents
Related Articles