|SLS AMG E-CELL Click to enlarge.|
Mercedes-AMG plans to begin production of the SLS AMG E-CELL electric super sportscar (earlier post) in 2013, said Dr. Dieter Zetsche, Chairman of the Board of Management of Daimler AG during the company’s press conference at the North American International Auto Show. Mercedes first announced development of the electric gull-wing sportscar in July 2009.
The four synchronous electric motors in the SLS AMG E-CELL deliver a combined 525 hp (392 kW) of power and 649 lb-ft (880 N·m) of torque. The four compact electric motors each achieve a maximum rpm of 12,000/rpm and are positioned close to the wheels, substantially reducing unsprung masses compared with wheel-hub motors. One transmission per axle transmits the power.
The race for the best super sportscar with electric drive is on.—Dieter Zetsche
The SLS AMG E-CELL drive features a liquid-cooled, high-voltage lithium-ion modular battery pack with an energy content of 48 kWh and a capacity of 40 Ah. The maximum electric load potential of the battery, which consists of 324 lithium-ion polymer cells, is 480 kW. One of the technical bases of this performance is the intelligent parallel switching of the individual battery modules, which also helps to maximize the safety, reliability and service life of the battery, according to the company. The 400-volt battery is charged using targeted recuperation during braking.
|The incorporation of the electric drive components required no changes whatsoever to car’s weight-optimized aluminum spaceframe. Click to enlarge.|
The electric-only drive system was factored into the SLS development process at the concept phase. Its packaging is designed for the integration of the high-performance, zero-emissions technology, enabling the four electric motors and two transmission units to be positioned as close to the four wheels as possible and very low down in the vehicle.
The same applies to the modular high-voltage battery—its component parts are located in front of the firewall, in the center tunnel and behind the seats. Benefits of this solution include the vehicle's low center of gravity and balanced weight distribution—ideal conditions for optimum handling, and something the electric-drive SLS AMG shares with its gasoline sibling.
The additional drive to the front wheels necessitated a new front axle design. Unlike the series production vehicle with the AMG V8 engine, which has double wishbone suspension, the SLS AMG E-CELL features an independent multi-link suspension with pushrod damper struts. This is because the vertically-mounted damper struts in the series-production SLS had to make way for the additional drive shafts. Frequently found in racing cars, the new horizontal damper units are actuated via separate pushrods and transfer levers.
Another distinguishing feature is the speed-sensitive, rack-and-pinion power steering, with the power assistance operated by electro-hydraulics rather than conventional hydraulics.
The braking system on the prototype features AMG ceramic two-piece brakes, available as an optional extra on the series production model. It delivers extremely short stopping distances, a precise actuation point and outstanding fade resistance, even under extreme operating conditions. The generously dimensioned, radially floating rotors measure 15.83 x 1.54 inches at the front and 14.17 x 1.26 inches at the rear and are made of carbon fiber reinforced ceramic composite material connected to aluminum hubs.
The ceramic brake discs are 40% lighter than the conventional, gray cast iron brake discs. This reduction in unsprung mass improves not only handling dynamics and agility, but also ride comfort and grip. The lower rotating masses on the front axle also ensure a more direct steering response—which is especially effective in high-speed cornering. The ABS and ESP systems have been adapted to match the particular operating spectrum of the permanent all-wheel drive.