Chevrolet’s 2014 Spark EV will be the first production electric vehicle capable of quick charging on direct current (dc), or conventional ac charging using SAE International’s revised J1772 standard and new Combo Connector, when the car goes on sale next summer. The five-door Spark EV is General Motors’ first production battery-electric vehicle and features a GM-designed-and-produced traction motor. It will have a $25,000 base price before U.S. and state tax credits, which can drop the vehicle price by as much as $10,000.
The car was unveiled to the public at the 2012 L.A. Auto Show. AEI was given a deep background review of the car at a media event earlier in November. An early test drive in San Francisco showed the car to have quick acceleration; GM engineers claim 0-60 mph (0-97 km/h) in less than 8 s.
GM plans to sell the Spark EV initially in California and Oregon, as well as in Canada, Europe, and South Korea, according to Larry Nitz, Executive Director of GM Global Electrification Engineering, who played a key role in development of the Chevrolet Volt.
The SAE Combo Connector enables both ac Levels 1 and 2 charging (110/120 and 220/240 V, respectively) as well as dc quick charging, formerly known as Level 3. According to Nitz, the car can be charged in about 7 h with a 240-V outlet. With the optional quick-charger incorporated into the Combo Connector, the Spark EV’s battery pack can reach 80% state of charge in 20 min. That’s among the fastest, if not the fastest charging for a plug-in vehicle to date, Nitz said.
A 120-V charge-cord set is standard. Charging can be monitored and managed remotely using the car’s OnStar smartphone app.
Nitz also claimed the car will have the best range in its segment but declined to specify until U.S. EPA testing is completed.
Spark EV’s 20 kW·h, lithium-iron-phosphate battery pack is liquid cooled with active heating and cooling. This design ensures optimal thermal performance in all ambient climates, as well as ensuring reliability for an eight-year, 100,000-mi (160,934-km) warranty, noted Bill Wallace, GM Director of Global Battery Systems. The pack is supplied by A123 Systems and contains 336 prismatic-pouch cells (3P112 type) arranged in four modules.
Wallace noted that the A123 pack used in the Spark EV is the same as the one used in the GM-Shanghai Sail Springo and has accumulated more than 200,000 h of testing.
The battery pack is designed to sustain multiple dc quick charges per day, Wallace said. The pack weighs 560 lb (254 kg), and its addition to the Spark along with the rest of the electric propulsion system (and combined with the deletion of the combustion engine and its related systems) contributed to a 400-lb (181-kg) overall mass gain compared with the conventionally powered Spark, according to Lead Development Engineer Trista Scheiffer.
The rectangular pack is located below the Spark’s rear seats, directly over the rear axle. It’s housed in a sealed, composite enclosure. The pack is situated in the same space used for the fuel tank in the conventionally powered Spark, which required minimal body modifications, Scheiffer noted.
In addition to the dc quick-charging capability, the Spark EV also debuts GM’s new 120-kW traction motor, which is neatly integrated into the car’s front-drive unit. The permanent-magnet electric machine weighs 400 lb (181 kg), was designed by GM, and is manufactured in the company’s White Marsh, MD, plant near Baltimore. According to E-motor Development Manager Matt Laba, the Spark’s motor features a bar-wound stator for better thermal performance and torque.
“We have intellectual property around the 20 different wire forms in this motor,” Laba told AEI, “as well as in the stator design, motor controls, and in the core machine design.” He explained that placement of the neodymium-iron-boron magnets went through thousands of design iterations to minimize NVH and optimize torque ripple.
See this GM animation of the Spark EV’s propulsion system: http://bcove.me/2qpl0vbx.
The Spark EV’s compact drive module may be the most cleverly designed and packaged element of the car’s propulsion system. Assistant Chief Engineer Mary Ann Jeffers explained (using a cutaway property) that the e-motor’s rotor connects to a planetary gearset that drives an output gear and the differential, which then spin the car’s halfshafts.
Smartly, her engineering team designed the drive unit to incorporate a number of components carried over from other programs, including the range-selection system (from GM’s two-mode hybrid transmission); the differential (from the 6T70 six-speed transaxle); and the traction inverter and oil pump (from the Volt).
Both the drive unit and traction motor are oil-cooled (with ATF), Jeffers noted, and use a liquid-to-air heat exchanger to moderate operating temperatures. Together they provide up to 400 lb·ft, which is a major factor in the Spark EV’s zippy acceleration performance.