BMW provides inside look at EV experiences

  • 26-Mar-2010 03:38 EDT
To capture increasingly critical electric vehicle knowledge in-house, BMW is building its own electric motor and transmission for the ActiveE and is assembling its own battery packs using SB Limotive lithium-ion cells.

BMW has revealed new research into the use of its MiniE battery-electric test fleet cars. The company says that the findings will guide the company’s ongoing development of a future battery-electric production model it refers to as the Mega City Car.

The company says that building its test fleet of converted Minis, and its new, larger fleet of BMW 1 Series-derived cars it calls the ActiveE, has been a useful experience in many regards. The company is learning about the challenges of assembling electric-drive cars so that it can do this more efficiently when they go into production, points out Rich Steinberg, Manager of Electric Vehicle Operations and Strategy for BMW of North America.

But just as important, by putting these cars into the hands of regular drivers in the real world, BMW is learning what aspects of the electric-car driving experience are acceptable to consumers and which still need improvement, he said.

For example, in a study conducted by Tom Turrentine, Director of the plug-in hybrid electric vehicle center at the University of California at Davis, it turns out that even the meager 100-mi (160-km) driving range of the MiniE was satisfactory for most of the cars’ drivers. Nearly half of the drivers achieved the expected range of 100 mi, and the majority of them were able to achieve a range of between 70 mi (112 km) and 100 mi, and they found that range to be acceptable, Turrentine reported.

Conversely, test drivers found the MiniE’s lack of a back seat and paltry cargo space intolerable, said Steinberg. Having learned this, BMW now knows that it would not be worthwhile to sacrifice too much cabin space in search of additional driving range, he said.

Even with the relatively short driving range of the MiniE, the test drivers did almost all of their recharging at home, according to Turrentine’s data. That means that the lack of a public recharging infrastructure may not be the obstacle to sales of electric vehicles that it was imagined. This suggests that the planned gradual roll out of electric models in markets believed best able to support them may not be necessary, which is good news for Midwestern EV enthusiasts plotting trips to California to buy electric cars not available in their home markets.

Some of the test drivers said they preferred the electric Mini to their own gas versions of the car, and 45% of drivers said they drove the MiniE more than the car it replaced. An amazing 100% of surveyed drivers said they like the MiniE’s “one-pedal” driving experience. The MiniE was programmed with aggressive regeneration on lift-throttle, so the electric motor provides most of the car’s braking. This means that drivers rarely even need to touch the brake pedal, an experience Steinberg likened to driving a golf cart.

Normally that is a negative comparison for electric cars, but in this case it is a characteristic drivers uniformly preferred, so that will continue with production electric cars. This is another example of BMW’s learning from experience with real customers, because the aggressive regeneration is a “relatively intrusive” technology, Steinberg acknowledged. Because the cars slow down almost as quickly as with the brakes, the MiniE is set up to illuminate the brake lights when the driver lifts off the gas pedal more than a little bit.

With the project’s recognition of consumer acceptance of electric drive even in fun-to-drive models like the Mini, BMW has focused more of its attention on the technology. For the ActiveE test fleet, BMW will assemble its own battery packs using cells provided by SB Limotive, a joint venture by Samsung and Bosch, Steinberg said. “This is an area we think we are good in and we can differentiate ourselves,” he said.

The company is also building its own electric motors and the transmission for the ActiveE.  The MiniE customer experience underscored the importance of having in-house knowledge of battery packs and electric motors, said Steinberg, while the single-speed transmission wasn’t a challenge even though the company normally sources its gearboxes from suppliers.

Another area where BMW plans technical innovation for future electric models is in heating systems. This is a sensitive area for battery electrics because of the ability of heaters to drain a battery and dramatically shorten an EV’s range.

The company has an innovative solution to this problem, but Steinberg wouldn’t reveal even the basic nature of the planned heating system, other than to say it will be more efficient than the electric resistance heat used in the MiniE. The ActiveE uses water that is heated by waste heat from the power electronics to keep the batteries warm in cold weather, and the future production model will also tap this heat source for cabin climate control, he said.

BMW will offer a smartphone app to let drivers precondition their car’s cabin remotely while the car is still plugged into the grid. This will reduce the burden on the batteries once the car is underway, because then the climate-control system will only need to maintain a comfortable temperature and not change the temperature of all the air and upholstery inside the car.

The Mega City Car will appear before 2015, targeting the world’s cities with populations of 10 million or more. It will be a dedicated compact model that does not share its design with existing gas models as the MiniE and ActiveE have.

The goal is for it to be as small as possible for convenient parking, while providing comfortable space for four occupants and a useable amount of cargo space. BMW is focusing on reductions in rolling resistance, aerodynamic drag, and vehicle mass to maximize the range of the car.

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