Electric propulsion courtesy of liquid-cooled lithium-ion batteries makes the gullwing-doored Mercedes SLS AMG E-Cell the supercar of tomorrow.
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The SLS AMG uses four electric motors, one to drive each wheel
By Stuart Birch 7:30AM GMT 23 Dec 2010
The cockpit of the gull-wing Mercedes-Benz SLS AMG E-Cell was totally silent as I looked over the long bonnet at the short, straight stretch of racing circuit. “Engage Sport-plus mode and floor the accelerator,” were my orders – so I did exactly that.
Four seconds later it was still almost silent inside the car but I had already exceeded 60mph and acceleration was building rapidly along a closed section of Valencia’s Formula One street circuit.
In theory, the E-Cell would have continued beyond 150mph but by then I would have been out of the closed section and mixing it with the city’s tumultuous traffic. Applying four huge composite ceramic brakes stopped that possibility in its tracks.
The only sound then was the resumption of my breathing.
This was Mercedes-Benz’s way of demonstrating an extraordinary supercar: zero tailpipe emissions, very few decibels, precise handling and the ability to literally deserve the application of that cliché beloved of those who experience rapid acceleration: electrifying performance.
Mercedes wants to show what can be done with electric powertrains, demonstrating that there need be nothing dreary about them. There is a similarity to the startling advance of diesel power from smoky, rattly dullmobiles to Le Mans winners such as Audi’s R10 TDI.
Technically, the SLS E-Cell is four-engined, with an electric motor placed close to each wheel it drives. In total, the synchronous motors provide a hefty 649lb ft of torque and have a combined power output of 392kW.
The electric SLS is about 660lb heavier than the conventional £157,000, 6.2-litre V8 SLS AMG (563bhp, maximum torque 479lb ft at 4,750rpm) but only felt it to a moderate degree when powering through tight bends or down a slalom test course. Its time to 62mph is only 0.2 seconds greater, thanks to the instant torque delivery of its motors, each spinning up to a maximum 12,000rpm.
There is only a modest whirring and humming during its rapid progress, and none of the snarling aural overtness that makes the regular car so memorable.
But it really doesn’t matter. The syrupy-smooth, aloof SLS E-Cell is a strong silent type that never needs to raise its voice.
Externally, the electric SLS looks very similar to its petrol sibling. Not so the interior, with different instruments and centre console, information including charge status of the battery and estimated range (up to 112 miles, but that depends on how much the performance is enjoyed). Transmission buttons are simply Park, Drive and Reverse.
The SLS AMG E-Cell is part of Mercedes’ “AMG Performance 2015” strategy that targets low fuel consumption and emissions while demonstrating that environmentally responsible cars can still be great fun to drive.
Its advanced technology includes liquid-cooled, high-voltage (400V) lithium-ion batteries positioned in the spine of the car and the luggage area, and a high-performance electronic control system. Cooling circuits are needed to control temperature of those and of the electric motors.
Mercedes has built only one example of the SLS E-Cell and has painted it a memorable shade called “fluorescent AMG lumilectric mango”; so if you don’t hear it coming you’ll certainly see it.
An electric version of the conventional SLS AMG supercar was planned from design conception, so packaging has not been a major challenge – although the E-Cell’s front suspension is a highly sophisticated multi-link set-up.
The prototype, which probably cost about £2million to build and develop, is not just a fanciful PR message. Mercedes-AMG boss Ola Källenius says: “It is continually our goal to reduce the fuel consumption and emissions of new models while at the same time enhancing the core brand value of performance.”
The SLS E-Cell could result in a limited edition production run by 2013 and would probably be available to lease.
Mercedes’ electric car programme is broad and includes the Smart Fortwo (available in Britain from 2012 to buy or lease), the A-class E-Cell (smooth and competent) and the hydrogen-fuelled B-Class F-Cell, neither of which is scheduled for Britain at present.
The production fuel cell is a bold step because there is only a minimal hydrogen infrastructure in Europe. But Mercedes believes it is vital to develop the technology. According to its research into the likely powertrain picture in 2020 and then on to 2050, Mercedes reckons that in 10 years one in 40 new cars will be electric-powered. But if oil prices rise steeply, in 40 years the picture could be very different. Then, petrol or diesel engines might power only about five per cent of new cars. The rest would be plug-in hybrids, battery power and fuel cells.
Hopefully the great great grandchild of today’s smooth SLS AMG E-Cell will be there to fill the supercar slot and, like Tate and Lyle’s golden syrup, deliver what it says on the tin: “Out of the strong came forth sweetness.”