Building a better car battery

By Alex Taylor III, senior editor

(Fortune Magazine) -- Since Nissan began developing lithium-ion batteries in 1992, it has increased their power density 1,100% and driven prices down to 1/16 of their old levels. But the biggest gains have come from the changeover in 2002 from cylindrical to more versatile laminated rectangular cells.

The shape and flexibility of the laminated battery enable it to be fitted in different cars without the need to redesign the cell itself. Laminated lithium-ion batteries also have twice the capacity and twice the power of a conventional battery of the same weight, yet are only half the size.

"In all-electric cars, Renault-Nissan's battery technology puts them clearly in the lead," says Wolfgang Bernhart, who has studied the field extensively for the consulting firm Roland Berger.

The Leaf's power source is a 24-kilowatt-hour laminated battery comprising 192 lithium-manganese cells. The pack provides electricity to an AC motor that produces 80 kilowatts (107 horsepower) -- comparable to an internal-combustion engine in a traditional subcompact. The motor also cranks out 207 foot-pounds of torque, sufficient for the Leaf's leisurely acceleration.

With a special boost from a three-phase charger, the battery can be replenished to 80% of its capacity in 30 minutes. Most private owners will opt to plug in at home for a slower overnight charge with a unit that will cost about $1,000. Nissan figures that with electricity at 11¢ to 12¢ an hour, the cost per mile for driving the Leaf is less than 3¢.

In April 2007, Nissan announced it was joining with NEC and its affiliated company, NEC Tokin, to form a joint venture for further battery research and the manufacture of the laminated batteries. Named the Automotive Energy Supply Corp. (AESC), the new company began operations in May 2008 and promised to invest $114.6 million over the next three years. NEC focuses on cell technology and electrode manufacturing, while Nissan manages mass production.

AESC built its first battery factory at Nissan's operations facility in Zama, Japan. Trial production began in 2009, and the factory will have a capacity of 65,000 by this year. Nissan is also gearing up manufacturing capability in Tennessee (200,000 units capacity by late 2012), the United Kingdom (60,000 units by early 2012), and Portugal (50,000 by 2012). Eventually it plans to make its batteries available to other automakers.

Advances in battery technology are coming quickly. Nissan reportedly has tested a next-generation battery that would extend the Leaf's range up to 186 miles while costing no more than ones used today. More improvements like that, and EVs will move much closer to the mainstream. To top of page