Fiat and Chrysler unveil 2014 battery-electric 500e

  • 28-Nov-2012 11:18 EST
2014 Fiat 500e cutaway.jpg

Chrysler engineers in Auburn Hills did a commendable job of packaging the 500e's electric propulsion system in the diminutive A-class hatchback.

Chrysler has lagged most of the industry in bringing electrified vehicles to production, but the 2014 Fiat 500e, officially unveiled Nov. 28 at the 2012 L.A. Auto Show, is a big step toward getting the automaker into the game. Unlike the rest of the growing 500 family that is based on Fiat’s global Mini platform, the battery-electric 500e—Chrysler Group’s first production EV—was developed by Chief Engineer Brett Giem’s American engineering team based at Chrysler’s Auburn Hills, MI, tech center.

“The 500e is not for electric-vehicle customers,” said Tim Kuniskis, Head of Fiat Marketing for North America. “Rather, we are positioning it for Fiat 500 owners who want to try a new technology.” The vehicle will be assembled in Toluca, Mexico, and launched first in California.

The A-segment EV is claimed by Chrysler to deliver an estimated 116 mpg-e (miles per gallon equivalent) city and 100 mpg-e highway electric-drive efficiency, with more than 80 mi (129 km) range per charge. The U.S. EPA is currently evaluating Chrysler data as part of the official rating process. Chrysler is claiming the 500e will accelerate from 0-60 mph (0-97 km/h) in less than 9 s.

Battery details

The car’s electric propulsion system features a 24-kW·h NiMgCo lithium-ion battery sourced from SB LiMotive, the Bosch-Samsung partnership. The 22-A·h pack is comprised of 97 cells. It is liquid cooled to ensure robust thermal performance in all markets and to help guarantee the car’s +80-mi range, Giem explained. Chrysler will warranty the battery pack for eight years.

Driving the car’s front wheels is an 83-kW permanent-magnet motor and single-speed final drive that Fiat has named “e-Drive.” The 3-phase synchronous electric machine generates 147 lb·ft (200 N·m). According to Giem, the system has 45 kW of total regenerative capacity. Chrysler engineers developed the car’s fully blended regen braking control strategy and included a “creep” function to better acclimate 500e customers who are used to the low-speed feel of torque-converter-equipped automatic transmissions.

The system is engineered with an auxiliary power module, which reduces the battery’s high-voltage output to 12 V to support the standard vehicle electrical system.

There are two cooling system loops—one for the battery pack and one for the passenger cabin. The battery thermal-management system, in addition to maintaining optimal operating temperatures for the high-voltage system, also incorporates supplemental passive cooling. Using the car’s brazed aluminum radiator, the system is configured to remove heat from the ethylene glycol-based coolant as air enters the front of the vehicle. The radiator also provides cooling benefits for the eDrive motor and the power inverter.

There is a high-voltage heating core for the interior. Giem said users can expect a 10% reduction of driving range on a cold day with the cabin heater turned on. The vehicle features remote battery preconditioning capability through a smart-phone app.

Architected for J1772 quick-charge

The 500e program was launched in 2010. An initial fleet of 40 mules grew to the current 100-car test fleet. The program was virtually in parallel to SAE International’s development of the revised J1772 standard for quick-charging EVs and PHEVs (go to www.sae.org/mags/aei/11484 to read more on the updated standard). The revision accommodates dc charging (previously known as Level 3) in addition to ac Levels 1 and 2 and features the new “combo connector” hardware that experts believe will dramatically reduce charging time for vehicles so equipped.

“The car is technically and architecturally prepared for the new SAE J1772 Level 3 quick charging, but we just timed out on the first-phase launch so we’re using Level 2 [240 V] hardware at launch,” Giem told AEI. He said upgrading the car to quick-charge capability, to be compatible with the new SAE combo connector, will mainly require retooling of the right rear quarter panel to provide a larger charge-coupler port and access door. The current round door is a carryover from the gasoline 500 and doesn’t provide enough clearance to fit the female charge connector or enough access clearance for the larger male combo connector.

The high-voltage battery is hard-mounted to the body structure and located longitudinally in the floor along the 500e’s centerline. The pack is considered a structural member and provides a 10% increase in bending stiffness, according to Giem. The packaging of the propulsion system is remarkable, given the diminutive platform. Giem’s team was careful not to let the battery intrude into the 500’s trunk, which has a special cubby for the charging cord. The rear passenger seats, already a tight squeeze on the conventional 500, are raised about 100 mm (4 in) to accommodate the battery pack underneath.

Adding 617 lb mass, reducing NVH

Chrysler engineers put a lot of work into the 500e’s aerodynamics, which are a traditional challenge on A-segment vehicles. Unique front and rear fascias, a more efficient rear spoiler, and new 15-in aluminum road wheels, along with underbody fairings, were worth 48 counts of aerodynamic drag, lowering the car’s drag coefficient to .311 Cd vs. .359 Cd on the conventional 500. Tires with low rolling resistance were designed specifically for the 500e.

Electrifying the 500 brought a 617-lb (280-kg) curb weight penalty vs. the base 500. The 500e weighs 2950 lb (1338 kg), and the car’s front-to-rear weight balance has shifted to a more rearward bias: 57/43%, compared to 64/36% on the conventional 500.

Chassis and suspension engineers designed the 500e’s suspension specifically for the additional mass, with a focus on retaining the 500’s fun-to-drive qualities. Spring rates are increased and the tuning of the front struts and rear shocks is unique to the EV. Calibration of the electronic power steering also is specific to the 500e, which features a 16.3:1 steering-gear ratio for improved responsiveness, according to Giem.

Eliminating the combustion engine put a new focus on improving the 500’s NVH characteristics. In addition to the major aero improvements, Giem’s team executed 12 product-specific improvements aimed at reducing cabin noise. They include new acoustic windshield glass; additional mastic patches and sound-deadening material on the floor pan, doors, rear quarter panels, and in the wheelhouses; thicker carpet layers; and an additional 8 mm (0.31 in)-thick acoustic pad installed in the rear floor area.

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