Chevrolet Volt Development Charges On
Source: GM Europe
Apr 6, 2008 - 1:02:08 PM
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Battery engineers develop new computer testing procedure, leverage global
resources to accelerate development of extended-range electric vehicles
(E-REV)
· Engineers integrate T-shaped battery into vehicle structure
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Designers improve aerodynamics to lower energy consumption
Engineers at GM’s battery test facilities have developed a new computer
algorithm to accelerate durability testing of the advanced lithium-ion batteries
needed to power the Chevrolet Volt for up to 40 miles (64 km) of electric-only
driving. This advanced computer program duplicates real-life vehicle speed and
cargo-carrying conditions, and compresses 10 years of comprehensive battery
testing into the Volt’s brisk development schedule.
The battery cycling
equipment is used around the clock in GM test facilities in Warren, U.S.A. and
Mainz-Kastel, Germany. It charges and discharges power from the prototype
batteries based on the Volt’s approximately 40-mile electric-only drive cycle.
Results from this test data will help predict the long-term durability of the
battery.
“Production timing of the Volt is directly related to our
ability to predict how this battery will perform over the life of the vehicle.
The challenge is predicting 10 years of battery life with just over two years of
testing time,” said Frank Weber, global vehicle chief engineer, Chevrolet Volt
and E-Flex systems. “The battery team is able to utilize human and technical
resources around the globe to reduce testing time.”
Testing the batteries
in the laboratory provides a predictable environment to compare technologies
under controllable situations. The batteries will soon be integrated into
“mule,” or test, vehicles with other E-Flex system components for on-road
tests.
Vehicle engineering
Engineering an
electric vehicle with a battery roughly 6 feet (1.8 m) long and weighing more
than 375 pounds (170 kg) requires innovation. The T-shaped battery will be
located down the center tunnel of the vehicle and under the rear seats. This
integration requires the battery to be treated as part of the vehicle structure.
Simulation data also indicates that the center placement provides greater
protection to the battery.
Engineering innovations are also required to
maximize the Volt’s 40-mile electric-only range and minimize the use of its
range-extending internal combustion engine. To reduce mass, the Volt is being
engineered with a relatively small fuel tank. This reduces weight, but still
provides a driving range in excess of 400 miles between
fill-ups.
Designing the interior
The battery
placement created interior design opportunities that led to several creative
solutions that improve aerodynamics and overall comfort.
“We made a
conscious decision to make the Volt a four-passenger vehicle to keep the roof
low, an important aerodynamic enabler,” said Bob Boniface, design director,
E-Flex. “As designers, we must be sensitive to the energy efficiency gains that
can be achieved by optimizing aerodynamics. This not only contributes to
improved fuel economy or extended range, but can produce beautiful exterior body
shapes and innovative interiors.”
“By having the battery in the middle,
we were able to move the occupants apart and give them more space,” said Tim
Greig, interior design manager for the Chevrolet Volt. “We also shrink-wrapped
the interior, particularly the doors, for comfort and spaciousness. There is no
wasted space.
“Being an electric vehicle with a battery down the middle
presented unique opportunities to our design team,” he said. “The net result is
a very creative and innovative design, appropriate for an electric
vehicle.”
Reducing drag
Aerodynamic drag, or wind
resistance, accounts for about 20 percent of the energy consumed by an average
vehicle, directly reducing fuel efficiency.
GM’s aerodynamics laboratory,
located in Warren, is the center of expertise for optimizing airflow. In
addition to fuel economy, range, emissions and acceleration are all affected by
aerodynamic drag. The cooling of components like brakes is affected by airflow,
as is cornering capability, crosswind response, directional stability and
on-center handling. GM’s aero lab allows for the testing and development of each
of these characteristics.
“After extensive aerodynamic testing of the
Volt, the vehicle now has a coefficient of drag that is 30 percent lower than
the original concept,” said Ed Welburn, GM vice president, Global Design. “It’s
not easy, but it is a necessity.”
The ongoing development of the Volt is
just one part of GM’s commitment to displace petroleum use in the auto industry
through a range of propulsion alternatives, including:
- GM is the leading producer of E85-capable biofuel vehicles, with more than 3
million on U.S. roads today. GM has committed to having 50 percent of annual
sales volume E85-capable by 2012.
- By the end of 2008, GM is expected to offer more hybrid models (eight) in
the United States than any other automaker.
- The Saturn Vue Green Line, Saturn Aura Green Line and Chevrolet Malibu
Hybrid will feature GM’s mild hybrid technology.
- GM’s two-mode hybrid technology is available in the Chevrolet Tahoe Hybrid
and GMC Yukon Hybrid, and will be added later this year to the Cadillac
Escalade, Chevrolet Silverado Hybrid and GMC Sierra Hybrid, delivering highly
efficient performance and full functionality.
- Going into production later this year is the front-wheel-drive Saturn Vue
Green Line 2 Mode Hybrid, expected to deliver up to a 50-percent improvement in
combined city and highway fuel economy compared with the current non-hybrid Vue
XR, based on current federal test procedures.
- Earlier this year, GM launched “Project Driveway,” the largest market test
of fuel cell vehicles in the world, lending 100 Chevrolet Equinox Fuel Cell
vehicles to everyday drivers. GM engineers will analyze customer feedback and
use it to develop the next generation of fuel cell vehicles.
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