Hollow aluminum extrusions keep power source prime in new electric vehicle
November 2011 - The functional fundamentals behind an electric vehicle do not deviate much from a traditional combustion car: It gets you from point A to point B with peace of mind that it will operate safely. A clean fuel source, quiet ride and cost are major draws for switching to an electric vehicle, while the hidden guts of the innovative fuel source may not receive immediate consideration. But with only a battery at the heart of the drivetrain, there are material design elements that set the car apart.
Coda Automotive, a Los Angeles-based electric vehicle startup and developer of lithium-ion battery systems, designed the chassis of its Coda Sedan to integrate the 728 lithium iron phosphate battery cells that turn the wheels. The cells are arranged symmetrically across the Coda’s chassis between the rear wheels and front axle at a low center of gravity, which stabilizes the car’s handling.
Phil Gow, vice president of battery systems at Coda Automotive, says the arrangement of components is important with such a large battery. “The packaging for the battery, thermal management system and electrical components needed to be precisely balanced for optimum performance,” he says. “Engineers had to balance new technology layouts and configuration in order to ensure passenger comfort and vehicle handling were optimized.”
Power-management components are located where a traditional gas tank would be, and the entire assembly is bracketed by aluminum air ducts. The ducts cycle air through a motor that heats or cools the batteries, depending on their temperature. “The battery supporting structure is made from custom aluminum extrusions that are welded, riveted and bonded together,” Gow says.
Aluminum extrusions are crucial because they provide an air intake to the battery compartment. The aluminum active thermal management system keeps the battery warm in cold weather, which maximizes range, performance and charging, while the cooling system sustains the battery’s longevity in hot weather.
Gow adds aluminum is ideal for this application not only for the ease of fabricating custom extrusions but also because of aluminum’s “light weight and corrosion resistance.” Therefore, rust isn’t a concern for the battery’s frame. On the exterior, the Coda’s body is comprised of “a variety of grades of steel, including ultra-high-strength steel,” he says. Additionally, the Coda’s 17-inch wheels are forged from aluminum alloys and ride on four independent MacPherson struts.
Global part sourcing
According to Coda’s company overview, it has a global joint venture with Lishen Power Battery, Tianjin, China, a manufacturer and supplier of lithium ion batteries whose clients also include Apple and Motorola. Because each vehicle contains hundreds of battery cells, “the cell and battery pack production are highly automated,” says Gow. “The quantity and level of high-voltage components is much higher than the typical vehicle.”
The battery delivers 36 kilowatt hours (approximately 150 miles in optimal driving conditions) at 333 volts. Equipped with a single-speed transmission, common in electric vehicles on the consumer market, the Coda’s 134 horsepower motor tops out at an electronically limited 85 miles per hour, according to Coda’s specifications.
Coda vehicles are assembled initially in Harbin, China, before Amports, an automotive processing company, completes the final assembly at its Benicia, Calif., facility. “The motor and inverter are both sourced from U.S. companies,” Gow says. Currently, California is the only state where the vehicles are available on the consumer market.
This past September, Coda opened its first consumer store in Los Angeles, the facade of which is constructed from recycled stainless steel, mixed with concrete and salvaged wood elements from Utah’s Lucin Cutoff Railroad Trestle—a nod to the environmental philosophy that underlies the company’s goals. Coda’s store, named the “experience center,” allows potential customers to test drive electric vehicles and get comfortable with charging an electric car.
“We want to open dialogue between consumers, provide a stress-free purchase experience and ultimately accelerate the adoption of electric vehicles,” said Phil Murtaugh, CEO of Coda, in a press release. MM