• Apr 4, 2008
If the Chevy Volt were a 150 mpg dairy cow, the General's marketing department would have a hand on every udder. The Volt is still more than two years from production, and the series hybrid is all over the Internet, TV, and magazines. When a vehicle promises as much as the Volt does, though, any update is big news. This time, engineers have come up with a computer algorithm to accelerate battery durability testing. The test decreases battery testing from ten years to two by duplicating real-life vehicle speed and cargo-carrying conditions in a controlled environment while constantly recharging the batteries. The next step for the Volt is test mules that can put GM's e-Flex system through more unpredictable conditions like snow storms and Michigan potholes.

Since the Volt's 375-pound battery pack resides down the center of the car and beneath its rear seats, GM had some unique packaging issues to optimize interior space. Volt design director Tim Greig described the Volt's four seats as far apart from one another, which gives the vehicle's occupants more personal space. Designers had to be keenly aware of aerodynamics when designing the Volt, which means a lower roof-line, yet a 6' 2" adult can fit in any of the four seats. For more on the Generals Chevy Volt update, go to Autoblog Green, or hit the jump to check out GM's press release.

PRESS RELEASE:

Chevrolet Volt Development Charges On

WARREN, Mich. – 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, Mich. 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.

"Extensive analysis in our battery labs is an important step in proving this technology. We expect to further validate these batteries when they are integrated into engineering development vehicles," said Weber. "The conditions in a vehicle – where the battery is exposed to shaking, moisture and rapidly changing temperature conditions – are much more extreme than the controlled settings of the lab."

Vehicle engineering

Engineering an electric vehicle with a battery roughly 6 feet long (1.8 m) 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.

"The battery is more than just an energy carrier; it's a structural component that affects many other aspects of the vehicle," said Weber. "It's an integral part of the vehicle that interacts with the vehicle's thermal and safety systems and chassis components."

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, whether it's occupant packaging or overall styling. This not only contributes to improved fuel economy or extended range, but can produce beautiful exterior body shapes and innovative interiors."

The battery pushed the occupants outboard, or to the sides of the vehicle, so the design team had to get creative with the sections of the roof structure to enable aerodynamics and provide adequate head room. The interior will accommodate a 6-foot 2-inch (99 th percentile) male comfortably in the front and rear seats.

"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.

Aerodynamics development begins with a 1/3-scale model where basic shape and major features are defined. The model includes a highly detailed underbody and engine compartment. Radiator and under-hood cooling flow are developed with computational fluid dynamic models. Simultaneously, computation development takes place to determine the aerodynamic drag of design alternatives. Development continues with full-scale models, where shape is refined and optimized for low wind noise. The development process concludes with a vehicle prototype validation of the math-based analysis and physical testing.

"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.

Additionally, GM provides more vehicles that achieve 30 mpg on the highway than any other manufacturer in the U.S. market. GM is also a member of the U.S. Climate Action Partnership (USCAP), a group of global companies and non-governmental organizations that support an economy-wide, market-driven approach to reducing carbon emissions.



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  • 29 Comments
      • 6 Years Ago
      "A hand on every utter"? Is that a pun I'm not getting or just another example of the blogworld's "Yesterday I couldn't spell writer and today I are one"?
        • 6 Years Ago
        If you really want to be correct, there is only one udder on a cow. The sentence should read, "a hand on every teat."
        • 6 Years Ago
        Teat would have been the right word... I really should milk at least one cow before talking about the udder.
        • 6 Years Ago
        Cuda- exactly correct, although someone might get the wrong idea.
        • 6 Years Ago
        Stephen: I'm glad you don't get it... that means it was just clever enough. I know I originally spelled utter wrong (fixed it, thanks.)

        Just imagine a plug-in Chevy dairy cow, with a bunch of guys in blue suits trying to milk it for all it's worth. That is the kind of stuff you would see on Looney Tunes if Warner Bros. were able to draw udders on cows. The thought of cow-milking marketing execs makes me laugh, but I guess nothing is ever universally funny.

        You can knock blogworld all you want, but ya do show up here every day to read what we have to say, so it can't be all bad.
      • 6 Years Ago
      Why does it take a special algorithm to test 10 years of use in 2 years when testing takes place around the clock? I mean, my car is running only about 2 to 3 hours per day meaning my car is on about 14% of the day. 10 years use in 2 year time assumes 20% use per day. Doesn't seem like an accomplishment...more like "yeah we run the thing around the clock."

      Also, I'm not too hyped-up over this vapor ware. Until GM produces a drivable reliable car at the dealer I'm not going to be the least impressed.

      Also, +1 for The Truth About Cars
        • 6 Years Ago
        Ronnie & LOL Correy,

        Thank you for the clarifying explanations to this post. Unfortunately, we not quite singing from the same sheet of music. I think the problem lies in my original explanation so let me try again.

        Ronnie, building from your paint-testing example I can see how an engineer can test real-world wear by essentially intensifying the environment. Theoretically this accelerates effects from salt, water, road debris, etc allowing engineers to both infer actual damage and extrapolate data to predict what would happen over a longer period of time.

        In the case of GM, engineers need to use a battery for 10 years then measure how well its holding up. This is simply too long to wait, of course, so they develop an algorithm that runs the test " around the clock" in order to speed testing.

        My contention is that this is not a breakthrough in testing. The reason is that over the 10-year life of a battery it will be used for a fraction of each day, say 15% or 3H:36M. Over 10 years that equals 1.5 years. This still allows for 25% down time to allow for cooling or change of environmental factors such as temperature and humidity and still make the 2-year window for battery development. Correct me if I'm wrong, but the battery can not sense "vehicle speed and cargo." It only senses faster or slower drain, or faster or slower charge. By simply draining and charging the battery at levels that look like the fat-burning workout programmed into my treadmill, engineers can simulate 10 years of driving. No special algorithm and no press release is needed.

        I suppose my larger point is that the continued reporting of non-news items will continue to set the VOLT up for failure by setting unrealistic expectations. Most customers will walk in to the showroom on Day 1 of sales and expect to see the flying cars from Back to the Future 2, replete with flux capacitor.
        • 6 Years Ago
        I guess that makes two of us Bob. I suppose if you could more accurately describe the need for fancy algorithms you would have.

        Anyway, thanks for putting me in my place while at the same time adding to the intellectual discourse surrounding this most-hyped of auto developments. I know your contributions in defending GM's engineering strategy will be rewarded with an honorary model designation: Chevy Volt Bob Edition. It will feature a Mr. Yuk sticker on the fuel filler door and a "DO NOT LICK" warning on the battery terminals.
        • 6 Years Ago
        You are a moron, not an engineer.
      • 6 Years Ago
      "...unpredictable conditions like ... Michigan potholes."

      Since when is a Michigan pothole unpredictable? I'm no math major, but I think the predictability of Michigan potholes is approaching "1."
      • 6 Years Ago
      Aww only people who are under 6'2 can sit comfortably in all seats? I am 6'4, so is my dad..my best friend is 6'5...any one of us would be uncomfy in this car and yet I hear I can fit in a telsa roadster just fine! (why do i think this? Because I fit in a lotus elise just fine)

      If i don't fit in a volt but I can fit into 300zx's and 350z's i will be upset :( I like eco sports cars (well this looks sporty at least)
      • 6 Years Ago
      Ugghh - We've got three kids, so no Volt for us.

      I wonder if GM plans any family-friendly PHEV efforts...
      • 6 Years Ago
      Just think that with almost no gas bill every month you can add another 15k to the price and still be paying the same as a regular car! There will also be reduced costs to run this thing and the brakes will last forever due to the regenerative breaking. Also they are testing more then one battery pack at one time and Toyota only seems to have negative things to say because they are competitors, that just got caught with there hand in the government hand-out jar.
      • 6 Years Ago
      They have a packaging problem with the batteries? I can help. Switch to hexagonal packing.

      http://mathworld.wolfram.com/CirclePacking.html
        • 6 Years Ago
        Tighter (hexagonal) packing might make cooling a bigger issue than it already is. That's my hunch, anyway.
      • 6 Years Ago
      Dang- at first thought that was a party fridge in console!
        • 6 Years Ago
        Haha that made me laugh out loud.
      • 6 Years Ago
      The Volt during commuting can easily be shown to produce an average of 284 MPG across all drivers (and that's without any workplace recharging!) Any estimate of 150 MPG is absurdly low. And since GM is reporting 44 miels of range,that would provide 350 MPG during commuting.
      The only obstacle to the Volt at this point is the EEStor
      supercapacitor. If that works, as everyone by now thinks it will, the Volt will transform into an all electric - no range extender needed.
      If you want news on the Volt, only www.gm-volt.com (run by a New Jersey neurologist) is the place to go.
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