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Nissan Bets on the Electric Car


Thanks to a higher-energy, lower-cost battery, Nissan believes the electric car is ready for prime time. But are consumers prepared for all-electric performance?
Charles J. Murray, Senior Technical Editor, Electronics — Design News, June 24, 2010
Dan Hofstadter deliberated for weeks before recently plunking down $99 to reserve a Nissan Leaf electric car. A Tucson-based consultant who specializes in engineering analysis, Hofstadter wanted to make sure everything about the Leaf – driving range, size, cost, reliability, emissions – would be right before making the deposit.

“The environment is probably more important to me than it is to the average person,” says Hofstadter. “But not to the extent where I’ll buy a car that inconveniences me.”

Clearly, Hofstadter isn’t alone. At the end of April, just a few days after Nissan began taking reservations, more than 6,600 people had lined up their deposits, despite the fact that the Leaf won’t be available until December. For industry observers, the large number of reservations is a sign that the appeal of electric vehicles (EVs) is creeping outside the realm of committed, EV-at-any-cost environmentalists, to people like Hofstadter. And that’s the way Nissan wants it.

“To buy this vehicle, there should be an economic rationale,” says Minoru Shinohara, senior vice president of Nissan’s Technology Development Div. “The customer has to believe it makes sense, compared to buying a conventional vehicle.”

With the Leaf, Nissan believes it has reached that economic plateau. Since shelving the electric Altra almost a decade ago, it has kept its eye on the all-electric prize, working non-stop on EV batteries. The automaker has pulled together big teams of engineers at its Technical Center and at its Advanced Technology Center in Atsugi, Japan, as well as at its Research Center in Oppama and its Operations Center in Zama. Their task: to build a higher-energy, lower-cost, EV battery.

Because electric motors produce immediate torque, EVs accelerate more quickly than internal combustion engines. Source: Nissan
Click here for a larger version

The Leaf’s engineering team says the resulting battery will take the car 100 miles between charges, without clogging up valuable space in the back seat or trunk. The key, they say, has been a dedicated 17-year effort that has resulted in a two-fold boost in the battery’s energy density. By packing more energy into less volume, the battery provides Nissan engineers with choices – longer range or smaller batteries, or an idealized combination of the two. That’s why they’ve been able to store the battery under the Leaf’s floor while still reaching 100 miles of range.

“The breakthrough happened in 2002 or 2003,” says Mark Perry, director of product planning for Nissan USA. “We changed the chemistry, went to laminate cells, and at the end of the day, we had twice the energy density. That allowed us to optimize the vehicle platform. Suddenly, we had a mass market vehicle concept.”

Inglorious History

For automakers, the idea of a mass market electric vehicle has been a technological Holy Grail since a string of EV failures a decade ago. Back then, Nissan’s Altra EV died, along with the GM EV1, Chrysler EPIC Minivan, Ford Ranger EV, Honda EV Plus, Toyota RAV4-EV and GM S-10 electric pickup. In the end, EV enthusiasts blamed a host of perceived troubles, but manufacturers were in lockstep on one issue: They needed a better battery.

The EV battery lacked energy density, they said, just as it had for nearly 100 years. Legend has it that Thomas Edison and Henry Ford collaborated on the challenge of building a higher-energy battery a century ago. Given five years, they said, they could lick the battery problem. But while they developed a product, their battery’s energy density was just a fraction of that of a gallon of gas, and the EV gradually disappeared.

When major automakers resumed the quest in the 1990s, they tried a succession of technologies: zinc-air; lithium-sulfur, zinc-nickel oxide, sodium-sulfur, lead-acid, nickel-metal hydride, lithium-polymer, lithium-ion and others. Nickel-metal hydride and lithium-ion emerged as strong candidates because of their higher energy density, but the cost was high. Meanwhile, the venerable lead-acid battery offered low cost, but its energy density numbers were just too puny.

Worse, high-energy battery technologies – lithium-ion being a case in point – typically suffer from high costs. Cost estimates vary dramatically (see sidebar), but even the most optimistic automakers agree that today’s lithium-ion battery cells cost around $500/kW-hr. Add cooling structures and battery management to that, and the entire pack comes to about $700/kW-hr, and that’s an optimistic figure. Some experts contend the real figure is closer to $900/kW-hr.

Given such costs, automakers face a dilemma. Most believe there’s a market, willing and anxious, for electric cars. But a big 40-kW-hr EV battery could cost $30,000 or more. All costs of the remaining vehicle must be placed atop that. At that point, the electric vehicle leaves the realm of the working man, who often can’t afford a second car that costs $40,000 or more, and who doesn’t want a primary car with a 100-mile range.

That’s why some automakers, such as General Motors, aren’t migrating to battery-electric vehicles for now. After famously shutting down the EV1 program, GM’s executives say they’ll be very careful about pursuing pure electrics. “What we learned from the EV1 is that if you have a limited amount of range and a less-than-predictable driving pattern, then you’ll always run across the possibility of range anxiety,” says Rob Peterson, a GM spokesman. “In general, people don’t want to plan their lives around charging.”

Lessons Learned

Against that backdrop, Nissan challenged the status quo by deciding to re-enter the pure electric car market. The company’s executives say they can’t point to a particular moment of decision, but the public learned of it at the Los Angeles Auto Show in November 2008. There, Nissan CEO Carlos Ghosn laid out his zero-emission vehicle vision in a way no one ever had. “In China there are 50 cars for every thousand people; in the U.S. there are 800 cars for every thousand people,” he told reporters. “We will need another planet if China catches up to the U.S.”

Although Ghosn talked about zero-emission vehicles on that November
day, Nissan engineers say the decision may have been reached as much as four years earlier. By that time, they’d had sufficient experience with their own monolithic lithium-ion EV battery and they knew the vital signs were trending upward. Power was up two-fold. Energy was up
two-fold. Cost was declining.

“We had a huge number of engineers dedicated to the (battery) project,” recalls Shinohara of Nissan. “It was the largest scale engineering focus we’ve ever had on a single technology, outside of engine design.”

Most important, Nissan engineers had learned from their foray into EVs with the Altra a few years earlier. There, they had employed thousands of cylindrical, flashlight-sized 18650 lithium-ion batteries. The little batteries, each not much larger than a AA-sized cell, employed a costly cobalt-based electrode.

In the 2002-2003 time frame, Nissan engineers began working with another battery design. Instead of a small cylindrical battery, they employed a laminate structure for the cell. That raised their volumetric efficiency, largely because stackable flat cells use space more efficiently, whereas cylindrical cells have voids between them. Moreover, engineers changed the battery chemistry, jettisoning the cobalt-based lithium-ion design and replacing it with a so-called “manganese spinel,” which uses a crystalline structure that remains stable, even during charging. In addition to providing greater energy density, Nissan engineers realized another benefit: Manganese was far less costly than cobalt.

“Suddenly, we had a battery pack that was horizontal, instead of vertical,” Perry says. “That way, you don’t have to give up rear-seat room or trunk space. We were able to stack these things like wafers, under the front seat and under the load floor.”

The big breakthrough, though, was the energy density. Energy density, which translates directly to driving range, had suddenly jumped two-fold. Nissan still won’t say what their energy density is, but experts estimate it to be between 140-150 W-hr/kg, a gigantic leap beyond what was used in earlier EVs.

“An energy density of 150 (W-hr/kg) is a great number,” says David Swan, founder of DHS Engineering, which specializes in battery-related research and development. “It’s a number we would have given our front teeth for back in the ‘90s.”

Beyond the Vehicle

How well Nissan has learned the lessons of electric car design is evident from the company’s choices for the Leaf. Some of the Leaf’s technology is carried over from the Altra EV of a decade ago, but with additions – sort of an “Altra-plus” approach.

The Leaf’s drive motor is a perfect example. It delivers a tad more pep than the Altra motor – about 107 hp (80 kW) for the Leaf, compared to 83 hp (62 kW) in the Altra. Speed is up, too. The Leaf tops out at about 90 mph, compared to 75 mph for the old vehicle. At the same time, however, Nissan engineers kept the technologies that worked. The Leaf, like the Altra, uses ac synchronous motors (Nissan won’t say, however, whether they still employ neodymium-iron-boron magnets).

Moreover, the battery control and motor control are a direct result of earlier experience. Having learned from the Altra, Nissan engineers carefully programmed the battery management algorithms to watch battery temperature, as well as charge and discharge. That way, they could conserve energy and eke out as much range as is feasible. “We know all of this by experience,” Shinohara says. “We learned, then we applied our knowledge to manage the state of power and energy in the battery.”

With the exception of microcontrollers and a few minor parts, virtually everything is done in-house. Motors and inverters are designed and built by Nissan. Battery modules are designed in-house, then shipped off to NEC Corp. for manufacturing.

The greatest lesson learned, however, goes beyond the realm of component design. With the Altra, Nissan engineers found that consumers were concerned with recharge time. In the minds of many, recharge time trumped range as the EV’s biggest drawback. Forget the 100-mile range, consumers said, they didn’t want to drive to a distant location and then find they had an eight-hour wait before they could return. To deal with the problem, Nissan executives began teaming with the U.S. Dept. of Energy (DOE), municipalities and private companies to begin the odyssey of making recharging simpler. Working with the Electric Transportation Engineering Corp. (eTec) and a whopping $100 million DOE grant, Nissan will deploy up to 1,000 battery electric vehicles in five states, which will install 12,500 220-V charging stations and 250 more 440-V fast-charge stations.

The key to such efforts could be the 440-V stations, which would enable electric cars to go from near-depleted to 80 percent recharged in 25 minutes. “You could drive 100 miles and have a sandwich while your vehicle recharges in the parking lot,” says Nissan spokesman Brian Brockman. “Then you could go another 70 or 80 miles before you’d have to charge
it again.”

At the same time, however, Nissan is also partnering with AeroVironment Inc. on the installation of home charging stations for the Leaf. The home charging stations, which combine charging algorithms with intelligent thermal management, are capable of charging a Leaf in about eight hours on a 220-V line. Nissan is working with AeroVironment, not only to provide the stations, but also to enable Leaf buyers to access a nationwide network of licensed electricians to install the chargers in garages. The charging stations could be a key part of the marketing puzzle for Nissan because, without them, many buyers would be looking at a 16-hour recharge on a 110-V power line.

“If customers want to do a one-stop shop, they can do it,” Perry says. “They can purchase the Leaf and have Nissan do the charger installation anywhere in the country.”

A New Beginning

By taking advantage of the growing nationwide infrastructure and the gradual improvements in battery technology, Nissan executives believe the Leaf may be in a position similar to that of the Prius of 10 years ago. The Leaf, they say, is ready to grab a share of the global automotive market. Its 480-lb battery pack is far smaller than the packs of a decade ago that filled trunks and rear seats. It’s less costly and still offers 100 miles of range. At the same time, the Leaf’s electric powertrain provides better acceleration than those of gasoline-burning vehicles and is significantly quieter

Moreover, Nissan executives believe today’s consumers have a different mindset than those of a decade ago. “The number of people who are trying to live sustainably is growing and growing,” Perry says. “They’re worried about the environment and they’re worried about what they’re leaving behind for their children. You can see it in all the market research data.”

The belief in EVs is also spreading to other corners of the auto industry. Ford, Chrysler, Mitsubishi, BMW, Infiniti, BYD, Daimler, Tesla and others have announced pure electrics.

Still, not everyone is on board. Toyota and GM believe the immediate future lies in plug-in hybrids. Many auto industry analysts are unconvinced, as well, largely because they believe the battery issue is still unsolved. “The energy density is a lot better,” says Donald Hillebrand, director of the Center for Transportation Research at Argonne National Lab. “But it still isn’t good enough to convince the bulk of consumers that they can rely on an electric vehicle.”

“It might be a losing proposition,” adds Donald R. Sadoway, professor of materials chemistry at MIT and nationally recognized battery expert. “But if it keeps the electric car alive in the minds of policy makers, then when we do find the right battery – which will be as good as lithium-ion but at a more acceptable price – we’ll be ready.”

Although Nissan plans to build 50,000 of the vehicles per year, the company’s executives have acknowledged that electric car adoption will be slow, at least in the beginning. But they’re prepared for the Leaf’s powertrain to play a back-up position to the internal combustion engine for some time. “We’re not saying that electric cars are our singular strategy as we move forward,” Perry says. “But in the end – 2030, 2040, 2050 – we’ll reach a point where the transportation sector has to switch over. We’re all going to have to do it.”
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Source: designnews.com

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