IEEE Spectrum May, 2017 - 13

eaton

cessors. Today's mild-hybrid standard is
48 volts, which allows for lighter batteries with fewer cells and requires far less
electrocution shielding.
Most mild hybrids employ a motorgenerator that absorbs braking energy to
charge a lithium battery and then returns
that energy to the engine's crankshaft
during acceleration. An example is the
electrified Silverado pickup that General
Motors began offering in California last
year and expanded in April to Hawaii,
Oregon, Texas, and Washington. The
technology cuts fuel use in city driving
by up to 13 percent: It helps keep half of
the V-8 engine's cylinders deactivated
and lets it turn off at red lights.
Daimler plans to make 48-V motorgenerators ubiquitous in Mercedes-Benz
vehicles, starting with an electrically
boosted S-Class sedan launching later
this year. Besides its motor-generator,
the mild hybrid's electrical system will
supercharge the turbo engine, eliminat-

mild yet electric: eaton's electrically
Assisted Variable speed supercharger uses
braking energy and engine exhaust to power a
mild-hybrid system.

ing the traditional exhaust-driven turbo's
torque lag.
Top-tier suppliers, meanwhile, have
pushed the mild-hybrid concept further. Both Ohio-based Eaton and Ricardo,
based in the United Kingdom, are testing
mild hybrids that use engine exhaust to
generate electricity, adding to the regenerative braking that charges the hybrid
battery. Mihai Dorobantu, technology
planning director for Eaton's vehicle
group, says the company is showing off
a demonstrator vehicle to automakers
at its proving grounds in Marshall, Mich.
The challenge to selling such efficiencyboosting technology is that it increases
a vehicle's sticker price. GM charges a
US $500 premium on its hybrid Silverados. With gas prices in the United States
currently averaging a low $2.30, the added

system will take seven years to pay for
itself. Most consumers-and the automakers serving them-do not make such investments unless mandates force their hands.
Mild hybrids were projected to make
up 18 percent of cars and light trucks sold
in 2025 in the United States, according
to a joint analysis issued last year by the
EPA, the National Highway Traffic Safety
Administration, and California regulators. That number was 2.5 times as large
as the combined share projected for full
hybrids and battery EVs.
That projection looks optimistic under
the Trump administration, according
to Abuelsamid. He says Trump's EPA
may retain Obama's standards but make
them more flexible and lower penalties-
in practice, rendering the rules voluntary. Abuelsamid says he had expected
significant mild-hybrid growth from
2019 in the United States, but that could
be delayed by four to five years.
Delay could hurt companies like Eaton
that spent big on development. "Weakened or delayed standards would ultimately leave technology on the table," says
Nic Lutsey, program director at the Washington, D.C.-based International Council
on Clean Transportation (ICCT). A recent
survey of suppliers by Ricardo found that
70 percent favored maintaining the EPA's
rules. "They've made...those investments,
and now they want to make sure there's
still a market for them," Lutsey says.
That said, suppliers still have tougher
mandates in markets such as China and
Europe to rely on. European regulations,
for example, limit gasoline-fueled cars
to just 4.1 L/100 km (57 mpg) from 2021,
and will require a further 17 to 28 percent
reduction from 2025. Of the 5.6 million
48-V electric turbochargers that Navigant
projects will be installed worldwide in
2025, 85 percent are for Europe and Asia.
As Dorobantu puts it, the "quest for
higher and higher efficiency in vehicles"
are "macro trends" that are independent
of the EPA's standards. "It is those macro
trends that are guiding our investments."
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Table of Contents for the Digital Edition of IEEE Spectrum May, 2017