Fleet Maintenance - 26

Healy says. "With a passenger car,
you're typically making a 30-mile
commute to work every day, and then
parking in the garage and recharging
every night. So full electrification is
catching on more in the passenger
vehicle industry. That said, we think
it will still be quite a while before Class
8 trucks can go fully electric."
In the meantime, the hybrid
approach can make a lot of sense.
According to Healy, an electric axle
in a hybrid vehicle can help a fleet
save 5 to 10 percent on fuel in rolling
terrain areas, and 10 to 15 percent
in more hilly areas. When a truck
reaches an uphill climb, the electric
axle kicks in and helps relieve some
of the load placed on the engine. Then,
when travelling downhill, that same
axle can use regenerative braking to
charge the battery pack. As a result,
the truck never has to be plugged in
to recharge, which is a big efficiency
and convenience gain for fleets.
With an electric axle, electric power
from the truck is transferred to a
battery bank, control box, and cooler,
and then to the rear axle with an integrated motor. Healy says it is difficult
to put a drive system on a steer axle, so
the Hyliion system is not designed for
that right now. Instead, it focuses on the
two rear axles of the tractor.
Since the Hyliion system is a hybrid
system, the truck still needs diesel
power. Thus, a driveshaft is still needed to run from the transmission to the
front axle.
However, that is where the driveshaft stops. The electric axle is complete-

» Dana's Spicer eS9000r e-Axle is
an integrated motor, transmission
and axle power system designed for
Class 4, 5, and 6 vehicle applications.
It is shown here with the TM4 SUMO
MD motor/inverter system that is
designed to interface directly with
standard rear differentials and/
or gearboxes and/or e-Axles.
Photo courtesy of Dana

ly independent and located at the rear.
Fleets must also mount a battery box,
cooling system, and controls box to the
frame of the truck.
"All of these components connect
together and work in unison," Healy
says with respect to the Hyliion
system. "When the truck accelerates,
we are passively reading the CAN bus
of the truck so we know how hard the
engine is working and how much fuel
is being consumed. We also have our
own algorithm with our software that
is analyzing the data coming off of
the truck. Our system then determines when it is appropriate to kick
in and supplement what the engine
is already doing."
A side benefit of the Hyliion hybrid
system is that a driver can use the unit
that cools the system batteries to function as an auxiliary power unit (APU)
when the driver is sleeping in a rest area.
That could potentially spare a fleet the
need to invest in a separate APU.
In addition to long-haul, Trost says
there are many other fleet applications
where an integrated electric axle can
be beneficial - from Class 4 all the way
through the variants of Class 8. Dana
is developing a full lineup of e-Axles
for 6- to 12-meter buses, as well as
medium duty vehicles such as city

As the technology evolves and more
OEMs begin to adopt these types of
integrated electric solutions, even bigger
changes could be on the horizon.
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26 Fleet Maintenance | June 2019
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