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As BMW i3, i8 electric cars charge to market, more tech details emerge

Consumer Reports News: October 05, 2011 05:28 PM

BMW is taking the next step in the development of plug-in hybrids with its i3 electric car due out at the end of 2013. The i3 will be a city car made of carbon fiber that BMW plans to sell in big cities around the world.

Last year, BMW announced the i3 would come with an optional gasoline-powered range extender—an internal combustion engine that runs a generator to provide additional range once the batteries are depleted.

The Chevrolet Volt and the Fisker Karma have similar set-ups. Both use versions of General Motors’s Ecotec four-cylinder engine. The Volt uses an 84-hp, 1.4-liter version, while the Karma uses a 260-hp, turbocharged, 2.0-liter version. Intended as a city car, the i3 will use a much smaller gas engine.

This follows more in line with what Dr. Andy Frank—a mechanical engineering professor at the University of California who is considered the father of the plug-in hybrid—had in mind years ago. (A plug-in hybrid is another name for an extended-range electric vehicle.) His idea included reducing the size and capability of the gas powertrain to make up for the extra weight of the batteries.

At a BMW-hosted event in New York City yesterday, we had an opportunity to meet with key people on the i3 development team, to learn more about this intriguing car and the technology within it.

BMW-i8-concept-pr-f.jpgWhen asked whether the i3 would use an engine from BMW’s car or motorcycle parts bin, Chief Engineer Ulli Kranz, initially demurred. But his eyes lit up when it was suggested that a motorcycle engine might be a perfect fit for such a car. At the same event, BMW announced that its upcoming i8 plug-in hybrid supercar will use a small three-cylinder engine, boasting 220 hp, to drive the rear axle. BMW has claimed the i8, which will cost more than $130,000, will have acceleration times of less than five seconds from 0-60 mph. Reports have noted that the electric motor on the front axle is good for 260 kW, or 349 hp, though we’re not sure how much of that it will use. Presumably most of its power will come from the electrically-driven front wheels.

In electric cars, BMW has said, reducing the overall weight has an exponential effect on reducing weight and cost in the battery and thus boosting performance and range (and reducing charging times). That’s why the i3 is made of carbon fiber and aluminum.

The i3 will use an all-aluminum chassis that will house all the drivetrain components, including flat-format prismatic lithium-ion batteries (made by Bosch and Samsung, and assembled by BMW), and an electric motor on the rear axle. Kranz estimates the carbon fiber that sits on the chassis will offset the total weight of the batteries, saving about 500 pounds. A further benefit, these smaller batteries will reduce charging time. The batteries will be liquid cooled, which will allow owners to pre-heat and pre-cool the cabin, and thereby minimize the effect of cold weather on range.

Kranz also announced that the car will be 100-percent recyclable. That’s right, 100 percent including the batteries. To aid that goal, the i3 will make extensive use of naturally grown fibers in the interior, including the dashboard and seats. BMW believes that sustainability will be seen as a luxury feature when the car goes on sale.

The i3’s drivetrain will be tested in BMW’s upcoming Active-E electric car, a 1 Series coupe converted to electric power. Unlike BMW’s previous electric car, the Mini-E, the Active-E won’t have its back seat consumed by batteries. The new 32-kWh flat-format battery pack and its cooling system are smaller than the 35-kWh battery pack in the Mini-E. Kranz says this is the drivetrain prototype for the i3.

The i3 will roll out in major cities around the world, including the Mini-E markets. It will include two new cities in the United States: Boston and San Diego. Other U.S. cities include: Los Angeles, San Francisco, Sacramento, and New York (including New Jersey and Connecticut suburbs).

Rich Steinberg, manager of BMW’s electric-car programs in the United States, says the company is focusing on cities that have planned for electric vehicle rollouts and have some public charging infrastructure in place to ease electric-car buyers’ “range anxiety.” Of course, that would not be an issue for owners of the version with the optional range-extending gasoline engine. He says he sees public infrastructure as eliminating a psychological barrier, even though BMW’s analysis shows most electric-car drivers will charge at home.

BMW expects that between 5 percent and 15 percent of cars will plug in for some or all of their power by 2020.

The i3 will fit in with other electric cars on the market such as the Chevrolet Volt and the Nissan Leaf. Like the Leaf, the i3 is targeting about a 100-mile range without the range-extending gas engine. Our just-released test of the Leaf has shown that its claimed 100-mile range is about 75 miles in the real world (and about 90 miles on an ideal day). Our tests show electric cars are very inexpensive to run. If BMW’s weight saving technology can bring down the required size and cost of the batteries, that could strengthen the case for electric and plug-in hybrid cars.

Related:
Preview: BMW i3 and i8 plug-in cars

Eric Evarts

   

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