Paris show: Benz debuts production SLS EV

THE most powerful production vehicle to come from Mercedes-AMG runs on electricity, in the form of the gullwing-doored SLS AMG Coupe Electric Drive unveiled at this week’s Paris motor show.

Taking the gong for world’s fastest electric production car, the SLS ED deploys its 552kW power output and 1000Nm of tyre-toasting torque through all four wheels via a quartet of electric motors.

Despite the prodigious outputs eclipsing the petrol version’s 420kW and 650Nm, a 548kg lithium-ion battery pack and 180kg worth of electric motors conspire to blunt the sprint to 100km/h by a tenth, to 3.9 seconds, and top speed is restricted to 250km/h.

For comparison, the Audi R8 e-tron develops 280kW of power and 820Nm of torque, accelerating from 0-100km/h in just 4.6 seconds on the way to a restricted 200km/h top speed.

The most 215kW/295Nm Sport variant of Tesla’s now discontinued Roadster – the original electric sportscar – could hit 212km/h and sprint to 100km/h in around 3.7 seconds.

Fetching a cool €416,500 ($A515,000) on the German market, the SLS ED was shown at Paris bathed in a stunning ‘electricbeam magno’ blue chrome paint finish that will be a no-cost showroom option and featuring AMG’s latest perforated grille mesh design.

A claimed driving range of 250km is available from the huge 60kWh battery pack, which pumps out 400 volts and has an electric load potential of 600W – statistics Mercedes-AMG says are “absolute best” in the automotive sector.

Audi’s R8 e-tron has a 49kWh battery providing a claimed 215km range but the Tesla Roadster’s 56kWh pack can manage a maximum range of 394km.

Driving each wheel with its own motor has endowed the SLS ED with a ‘Torque Dynamics’ feature that enables precise and fast-acting drive and braking control for each corner of the car.

The system has traction, handling, safety and ride comfort benefits while minimising the need for intervention from electronic safety nannies like electronic stability control and traction control.

A drive mode selector with Comfort, Sport and Sport Plus settings alter the drivetrain and Torque Dynamics system characteristics depending on driver mood and conditions.

Mercedes-AMG carefully located the battery pack and drivetrain components in the vehicle to achieve a low centre of gravity and optimum weight distribution to keep its dynamic abilities as close to the petrol-powered model as possible.

Each motor can spin up to 13,000 rpm, producing maximum torque from virtually standstill for quick responses, linear power delivery and vibration-free propulsion compared with the rumbling V8.

Mercedes-AMG says it did not mount the motors in the wheel hubs as this would result in too much unsprung mass, to the detriment of agility and ride quality, but placed them inboard, driving through axially-mounted transmissions.

To accommodate the front driveshafts, engineers had to redesign the front suspension, using race-style, horizontally-mounted push-rod dampers like the Lamborghini Aventador and McLaren 12C.

Steering is power assisted by an electro-hydraulic pump and the regenerative braking system is backed up by hefty, yet lightweight, carbon-ceramic friction brakes with huge 402mm front rotors and 360mm rear discs.

Precise control of the battery pack’s operating temperature, charging and discharge are said to extend its life and improve its efficiency.

In cold conditions a heating element is used to quickly bring the battery pack up to optimum temperature or in hot weather a cooling circuit comes into play, boosted by the vehicle’s air-conditioning system where necessary.

Temperature of the four electric motors and associated power management electronics are also controlled via a second cooling circuit.

The battery pack is made up of 12 modules each containing 72 Li-ion cells arranged to make best use of the available space, with individual cells linked using a parallel circuit said to “maximise the safety, reliability and service life of the battery”.

Mercedes-AMG in Affalterbach and Mercedes AMG High Performance Powertrains in Britain collaborated on the SLS ED project, using experience gained while developing the Kinetic Energy Recovery System (KERS) used in Formula 1 racing since 2009.

As a result, the SLS ED has a sophisticated regenerative braking system that enables “targeted recuperation” of energy to charge the battery under deceleration.

Customers can opt for a wall-mounted 22kW fast charger for their home, which tops the battery up in three hours compared with a lengthy 20-hour wait when using a standard outlet.

Lacking the sonorous V8 exhaust note that has become an AMG selling point, the SLS ED’s development team came up with a synthesised sound that “captures the exceptional dynamism of this unique super sports car with electric drive”.

A start-up tone is followed by a driving soundtrack that varies depending on whether the car is accelerating, at which point it sounds “incredibly dynamic”, while a subdued background note is present while cruising and a different tone is audible during regenerative braking.

All the while, a “sound cleaning” feature of the standard 11-speaker audio system cancels out unwanted background noise.