Early prototype suggests production version will be every bit as entertaining to drive as it looks

What is it?

The SLS E-Cell. A very new, very yellow plug-in electric supercar that is undergoing intensive development at AMG’s skunk works on the outskirts of Stuttgart, with sales set for late 2012.

The SLS E-Cell driven here is the first running prototype Mercedes-Benz’s AMG division has constructed as part of a three year development program for the new car.

As its familiar appearance suggests, the SLS E-Cell uses the same aluminium intensive body shell as the SLS AMG with some slightly different detailing, including a totally flat undertray to lower the overall drag co-efficient.

However, some serious changes have taken place underneath. In a move that provides it with a weight distribution of 46:54 front-to-rear and lowers the crucial centre of gravity by 24mm over its petrol engine sibling, Stuttgart’s new age supercar uses four individual motors – one at each corner.

They combine to produce 526bhp and a mighty 649lb ft of torque. By comparison, the SLS AMG’s naturally aspirated 6.2-litre V8 delivers 563bhp and 479lb ft.

But while the SLS AMG places its drive through the rear wheels, the SLS E-Cell gets it down via two individual transmissions from Getrag – one mounted on each axle - to all four wheels. Mercedes-Benz has also provided it with torque vectoring.

Other changes? The packaging of the two motors up front has also required a rethink of the suspension; the standard SLS’s double wishbones makes way for a new multi-link arrangement complete with space saving pushrod dampers. The rear multi-link set-up, on the other hand, remains largely unchanged.

The electric motors draw from a bank of lithium-ion batteries mounted under the bonnet, down the middle of the floorpan and behind the seats. They have a capacity of 40Ah, are rated at 48kWh and add a hefty 450kg to the car’s weight.

Recharging is via a multi-pin 240 volt plug, with total recharge time of eight hours at 16 amps. With an external 240 amp charger this can be reduced to less than one hour, although the values are in no way final.

The SLS E-Cell also uses a sophisticated brake energy recuperation system to continually recharge the battery pack with electricity created under braking.

The brakes themselves use lightweight carbon ceramic discs – 402mm in diameter up front and 360mm at the rear. They’re the same hydraulically operated units available as optional equipment on the SLS AMG.

What’s it like?

Press the start button of the SLS E-Cell and its futuristic looking instrument panel lights up in an impressive burst of blue and green. But there’s no sound. No nothing...

Applying the small amount of throttle sees the hi-tech Mercedes-Benz glide away from standstill with only the muted roar of tyres over bitumen, the action of the suspension and the sound of loose stones being thrown up into the wheel arches providing evidence of progress.

You’re also more aware of changes in the road surface – the roar of the tyres, which constantly alter in pitch as the road begins to open up and speeds rise. Wind noise around the exterior mirror housings also becomes a continual factor as speeds rise.

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It might weigh a good deal more but the SLS E-Cells kicks with a force comparable to the SLS AMG – and it does this instantly without the need to change gear at any speed. The thrust is seamless and, while achieved in virtual silence, is even more brutal than the claimed 0-62mph time of 4.0sec suggests.

Keep your foot planted and you reach 124mph in just 11.0sec. To preserve the level of charge, top speed is limited to 155mph – just 13mph short of the SLS E-cell’s theoretical top speed.

The SLS E-Cell doesn’t handle quite as well as the SLS AMG at this early stage. But given that the prototype weighs close on 2000kg, its overall dynamics are a revelation compared to some of the half baked electric cars that have gone before it.

One area where it really excels is traction. With four motors powering each wheel, it stomps out of corners with a level of athleticism equal to the SLS AMG.

If there is a weak link right now, it is the steering. The electric system is highly geared but it lacks the responsiveness of the hydraulic set-up found on the SLS AMG. It also fails to provide sufficient self centering when you’ve wound on a good amount of lock, leaving you to feed it back on the exit of corners.

Should I buy one?

There’s little doubt this car will be a hit among wealthy early adopters looking to set themselves apart from the motoring masses. The interesting thing is that Mercedes-Benz says the car will not be offered on lease but rather sold outright, which should also tempt collectors seeking an investment.

On the promise shown by the early prototype driven here, we’re confident the production version is going to be every bit as entertaining to drive as it looks – garish paint scheme and all.

Join the debate

Add a comment…
dpeilow 3 July 2010

Re: Mercedes-Benz SLS E-Cell

The article states that the recharge time is 8 hours at 16 Amps. In the paper magazine it is less committal with:

"Nor can we confirm whether the claimed eight-hour charge time is possible on a 16-amp/240-volt system, such as the UK's."

Leaving aside that a standard UK plug is in fact 13 Amps / 230 Volts, this is in fact easy to confirm from your article:

The battery is stated to be a 48kWh one.

16 Amps x 240 Volts gives 3840 Watts, the available power to charge.

48,000 Watt hours divided by 3840 Watts gives 12.5 hours charge time.

However, this assumes 100% efficiency. In reality charging is more like 90% efficient, so in fact the charge time on a normal plug will be closer to 14 hours.

I suspect that the claimed 8 hour charge time is when the car is plugged into a 32 Amp outlet, which is fair enough as they are very easy to install and can be had for less than £10 in Screwfix.

At the end of the day though, this is schoolboy maths, yet it seems to be wrong every time I read an electric car article.

ciz 29 June 2010

Re: Mercedes-Benz SLS E-Cell

It's a pity they don't just get a small electric car out that normal people can buy, imagine an a-class that costs the same as a normal model, thats when one of these big corps wins . This is just window dressing

ACCobra427 25 June 2010

Re: Mercedes-Benz SLS E-Cell

So it's slower and heavier (normal SLS), worse at handling has a 100 mile range (optimum!), 8 hours to recharge (cost?) at 16 amps, 450kg's of lithium ion batteries (nice and safe and great for the environment, haha) that will be completely knackered after 2-3 years and will probably cost, what, £10,000 to replace? It has no soundtrack other than the whine of motors (with lots of rare-earth magnets) and tyre noise and you dare not put the headlights or A/C on in case you run out of go-go juice before you get to wherever you're going.

What is there not to like?!