Fuel Smarts

The Case for On-Board Electrification in Class 8 Trucks

February 2018, TruckingInfo.com - Feature

by Jim Park, Equipment Editor - Also by this author

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This schematic drawing illustrates some of the potential for off-boarding drive components to lessen parasitic loads on engines. Source: Eaton
This schematic drawing illustrates some of the potential for off-boarding drive components to lessen parasitic loads on engines. Source: Eaton

The business case for electric trucks is no longer in any doubt. Even with their limited range, battery powered light- and medium-duty trucks work very well in applications tailored to those constraints.

While the case for battery-powered, long-haul Class 8s is still iffy, there’s no question that on-board electrification can take some of the load off the main diesel engine, allowing for greater operational flexibility and efficiency.

The move toward 48-volt electrical systems is still in its infancy, but SuperTruck concept fuel efficiency truck projects from Volvo and Navistar have shown they work. Likely applications for 48-volt power include HVAC, all-electric power steering, accessory drives like coolant and oil pumps, air compressors, engine fans, hybridization, etc., possibly right up to an electromechanical valve-train that can be very precisely controlled for improved engine efficiency (still maybe a decade away). We’re very restrained today by our legacy 12-volt systems, but the SuperTruck research is helping to build a compelling case for a faster move up the voltage ladder.

Larry Bennett, Eaton director of engineering, technology and innovation, says electrification will play a pivotal role in trucking powertrain technology over the coming decade. “Engine makers would like to take as much as they can off the engine itself to reduce all those parasitic losses,” he says. “We can drive a lot of it off-board, and do a great deal more in terms of power management and distribution, all using the transmission as the controller.”

Bennett says, for example, the generator and starter could be mounted on the transmission rather than the engine. It would allow electrical power to be generated while driving, but also, if engine-off coasting is developed, the transmission would continue generating power (driven by the rear wheels), and all the electrically powered systems, such as power steering, the air conditioner and the air compressor, would continue to operate.

Also, since all the accessory systems would be electric, like the air conditioner, a 48-volt electrical system would be better scaled to run the system for longer periods than the current 12-volt battery systems. This of course would require a switch from our current 12-volt battery to some advanced type of 48-volt battery, but that would all happen as these systems evolved.

“Once we have the 48-volt power distribution system in place, driven from the transmission, the OEMs can develop plug-and-play components, like 48-volt power steering and HVAC that just plug into a power distribution module,” Bennett says.

Once such systems are in place, trucks could be equipped with a hybrid powertrain where the motor/generator is capable of low-speed maneuvering, like when docking, or providing a power boost to smaller displacement engines when climbing hills, for instance.         

Bennett says Eaton already has the components to develop power management systems and power distribution modules, and lessons have already been learned that make it possible to better manage batteries.


  1. 1. John Baxter [ February 23, 2018 @ 07:31AM ]

    True, for sure. Eaton demonstrated a hybrid power train some years ago on their Marshall Michigan test track. Hot topic, for sure!


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