PARIS MOTOR SHOW: Benz SLS AMG Electric v Audi R8 e-tron

It wasn’t long ago that the world’s electric cars were scattered around a few wannabe hippies. Then Tesla arrived with a Lotus-based sportscar and a sedan, both powered solely by electricity.

Now the world is about to see its first fully electric supercars hit production, with both Audi and Mercedes-Benz using the “electrifying” pun for their most expensive models.

Mercedes-AMG has finally unveiled the full production version of its thumping SLS Electric Drive at today’s Paris motor show. The SLS EV will start the ball rolling with an astonishing 1000Nm of torque and is officially on sale from right now.

It is a fabulous piece of engineering, delivering more power and torque than the standard SLS AMG, and it is a fraction quicker to 100km/h, too.

While it is not disclosing the weight of the electric SLS, you can expect it to be significantly heavier, not only because of its big battery pack but its four separate electric motors – all of which replace the standard car’s 6.2-litre petrol V8.

Each weighing 45kg, the four permanent-magnet synchronous motors combine to deliver 552kW of power, hurling the SLS to 100km/h in just 3.9 seconds.

It’s also all-wheel drive, thanks to having a single electric motor taking care of each wheel and each individual tyre will receive a unique amount of power.

Call it a step up from Torque Vectoring, because the car’s on-board computer will determine exactly how much power and torque each tyre can handle in a given situation and each motor will instantly deliver precisely what that given tyre needs.

It’s a solution that AMG calls “Selective All-Wheel Drive” and does away with any need for differentials, because AMG claims the SLS can now do the job of a differential far more precisely – without braking the wheels – to maximise grip, security and speed in any situation.

While the V8 SLS weighs 1623kg, expect the Electric Drive to (un)comfortably outweigh that, largely thanks to a 548kg ‘fuel tank’ of Lithium-Ion down its centre.

This 60kW/h unit is more like a series of batteries than one big battery, because it’s made up of a dozen modules, each with 72 Lithium-Ion cells in them.

Developed in close consultation with the Mercedes-Benz Formula One engine people in Brixton, England, the system contains a 400-volt battery unit, a control unit to convert its direct-current energy into three-phase, alternating-current electricity and two separate cooling circuits.

The Brixton operation has been dealing with the high energy charging and discharging that comes with KERS since 2009, and much of that rapid, high-power, high-reliability technology is exactly what’s needed in the SLS Electric Drive.

Benz admits the SLS Electric Drive will deliver a new style of driving, with huge amounts of mid-corner drive and a wall of instant torque each time its driver accelerates.

That its potential range at full power is only just beyond 10 minutes doesn’t phase AMG.

“That’s all you would get out of a Veyron at peak power, too,” said one AMG source, “But that’s not how people drive them normally.”

They don’t even charge them normally anymore, because the SLS Electric Drive will come with a 22kW Wall Box high-speed charger to fully recharge the batteries in three hours, though it would take 20 hours via a normal household socket.

The lack of noise doesn’t phase Benz either, because it will synthesise the sound with a range of high-performance notes derived from its V8 model.

But Benz won’t deliver the only production electric supercar this year. AMG has been trading electric-car potshots with Bavarian upstart Audi for more than a year, with Benz having journalists test the electric SLS first, then the Audi.

Audi thought it had gained the upper hand, using its R8 e-tron to set an electric car lap record of 8:09.99 on the Nurburgring’s Nordschleife loop, but the Benz will enter production first.

Audi claims the record-breaking R8 was, in fact, the production version of the R8 e-tron, a car which will officially be on sale before the end of 2012.

At 1780kg, it is almost certain to be lighter than the AMG SLS, thanks to a heavy reliance on carbon-fibre panels and support parts, but it will need to be.

It carries two asynchronous electric motors – one for each wheel – at the back and a smaller synchronous motor at the front, combining to produce 280kW of power and 820Nm of torque.

Its power number is just a little over half what the Benz offers, though its torque output is very strong. Torque is, after all, an electric car’s backbone. Besides, the R18 Le Mans winner from earlier this year had only 275kW, but could call on additional short bursts of 75kW for each front wheel.

The R8 e-tron runs to 100km/h in 4.6 seconds – again, slower than the SLS Electric Drive – and is limited to 200km/h (the Benz runs to 250km/h).

Audi claims it will deliver 215km of driving range in everyday driving and though the car only managed two consecutive hot laps on the Nurburgring, a high-powered petrol-engined car can use more than 60 litres of fuel with the same style of driving over the same distance on the historic German track.

Audi is particularly proud of its new battery system, with modular, plastic-encased Lithium-Ion cells that are mounted in the central tunnel and even arranged so they can move against each other to help absorb crash energy.

Inside, it’s similarly technical, with the navigation screen replaced by an iPad to help drive the car and run normal systems including navigation, climate control and audio.

But while the Audi and AMG will be the first serious electric supercars, they won’t have the eco-supercar scene to themselves for long.

Porsche and BMW are heading there, too, but with plug-in hybrids rather than pure electric cars.

Porsche’s 918 has, in fact, already slammed around the Nurburgring’s Norschleife about a minute quicker than the R8 e-tron, with a 7:14 lap a week ago.

It combines a twin-turbo 4.6-litre V8 petrol engine amidships with a pair of electric motors up front to deliver 585kW of power, a 325km/h top speed and a 0-100km/h sprint of 3.2 seconds.

While all of those numbers are true supercar numbers, its fuel economy claim of 3.0 litres/100km definitely isn’t.

It runs a parallel hybrid system, with each engine capable of turning at least one wheel all by itself, and is an all-wheel drive car.

Still, it will be lighter than the SLS Electric Drive, at 1700kg, and will travel up to 25km on pure electric power. In fact, it will be able to hit 150km/h in pure electric mode.

Porsche will build 918 of them, all in left-hand drive starting in September 18 next year (hence 918) and they will sell for (breathe deeply) $US845,000 apiece.

BMW is using its plug-in hybrid i8 as a flagship for its all-new eco brand, yet its swoopy supercar will cost considerably less than the 918 at about $300,000.

On sale by mid-2014, the i8 has a 165kW turbocharged 1.5-litre three-cylinder petrol engine turning the rear wheels and a single 96kW electric motor in charge of twisting the front axles via a one-speed gearbox.

All up, it will have 260kW and 550Nm of power for sub-five-second sprints to 100km/h. BMW claims it has up to 30km of pure electric range and, like the faster Porsche, an economy figure of 3.0L/100km.

It will be the lightest of the eco super-coupes at 1630kg, and will also be the quickest to recharge, with a 105-minute claimed zap time.

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