The SLS AMG E-Cell: Mercedes' fluorescent premonition

Despite its limitations, the Mercedes-Benz SLS AMG E-Cell demonstrates that, in the future, performance and responsibility need not be mutually exclusive.

Its flashy shape and wild green hue notwithstanding, the Mercedes-Benz SLS E-Cell supercar turned surprisingly few heads during a test drive in scenic Norway.

There's got to be something wrong. There's just gotta be. Either Norwegians are colour blind or their enthusiasm for cars is equal to my own for performance art and cottage cheese. I am driving a lime-green Mercedes-Benz SLS supercar, gull-winged no less, through rural Norway and for all the excitement I am generating I might as well be driving a rusted out 1.3L Ford Fiesta. I knew that Scandinavians were reserved, but this borders on the comatose. Even those who might be mistaken for car enthusiasts didn't blink an eye.

A gaggle of BMW drivers - including one guy in a 5 Series tricked out with lowered suspension and big rims, which, in this land of strictly enforced 80kph speed limits, passes for a supercar - barely gave the fluorescent apparition a second glance as I warp-sped by. Imagine your enthusiasm for the 25th annual rendition of your doddering grandmother's traditional Christmas jello salad and you have some idea of the ambivalence. Would it have been too much to ask for even one half-hearted head swerve?

And, as if a bright, lime-green Mercedes supercar wasn't uncommon enough, this particular SLS was rarer still, the very one and only electrically powered prototype of what AMG hopes will be an EV future. Yes, you read that right, AMG - Mercedes' in-house tuning division - is producing an electric car, their often over-the-top reputation going a long way to explaining why Mercedes chose to paint this emissions-free supercar the very same jarring hue - "lumilectric magno" in AMG-speak - that newbie motorcyclists and paranoid bicyclists don in their fluorescent "conspicuity" vests in the hopes we'll give them the wider berth normally reserved for "baby on board" bumper stickers. It truly is eye-catching and, anywhere but in Norway, it seems, would immediately command your attention.

But it's not just the prepubescent, look-at-me paint job that catches your eye. Beneath that dissonant skin, there's some wildly impressive performance statistics that do nothing to shame the SLS's already-formidable reputation. The four onboard 400-volt electric motors (one for each wheel working through individual, fixed-gear 5.5:1 transmissions), for instance, generate 533 horsepower and 650 pound-feet of torque, an unusual combination of power and torque for an electric vehicle (most EVs, like diesels, produce lots of torque but correspondingly little in the way of horsepower). It's all made possible by the high-revving nature - 12,000 rpm - of the Mercedes motors. They accelerate the E-Cell, claims AMG, to 100kph in a scant four seconds - just 0.2 seconds slower than the petrol-fed car - despite weighing some 300kg more than the stock SLS.

Indeed, a sense of unrelenting acceleration permeates the electrified SLS. Unlike the Tesla Roadster, which can boast nearly the same breathtaking acceleration to 100 klicks, the E-Cell doesn't "run out of breath" at higher speeds, sprinting to the 160kph (the most I was permitted in this test), relentlessly punching through the air on its way to a top speed that Mercedes says is well over 250 kilometres an hour.

That's if it is in its "Sport+" or "Manual" modes. This being a German car and German engineers loving their gadgetry, there is a knob on board that allows the four electric motors to be limited to 40, 60 or 100 per cent of their maximum output. The base "Comfort" mode's 40 per cent limitation, for instance, is the equivalent of a conventional car's consumption-reducing "eco" mode, extending the SLS's range. "Sport" allows 60 per cent of maximum throttle for extended range on the highway while both "Sport+" and "Manual" offer full warp engines. It's a well thought out system that covers parameters such as the basic amount of regenerative braking and the immediacy of the throttle response.

Where it all gets a little complicated is that the system also lets the driver alter the amount of regen braking. Unable to ignore the steering wheel paddles that the stock SLS uses for quick-shifting the double-clutch transmission, the gearheads from Affalterbach programmed four separate levels of regen accessible via those paddles. The problem is that it's nigh on useless - no one is going to alter the amount of regenerative braking for every corner - and unnecessarily complicated - certain levels of stronger regeneration aren't allowed until the battery pack has depleted a specific amount. A better solution would have been programmed specific levels of regen into the E-Cell's four basic modes and left it at that.

As for the perennial EV bugaboo, range, AMG claims the electrified SLS can travel 150 kilometres between plug-ins. However, I used about 60 percent of the battery's available energy (Mercedes generously - compared to current production EVs - allows its Li-ions to be discharged to 10 percent and charged to 95 percent of their maximum 48 kilowatt-hour capacity) in just 67 klicks indicating a maximum range of just under120 kilometres. And, yes, we had to sit around for a couple of hours while the batteries were juiced up before we could go home.

It's also worth noting that, with 48 kW-h of battery on board, it can take some time to replenish all those errant electrons. On Europe's higher-voltage 220V circuits a full charge would take eight hours (expect more than double that figure on our wimpy 110V systems) and an hour even when feeding from a high-tech (read expensive) 400V recharger. At least AMG is realistic about the E-Cell's intent. It is, like all AMG's products, says Pietro Zollino, AMG's global communications public relations manager, "a fun car," meant to showcase the company's talents but also show that the future that "performance and responsibility" are not mutually exclusive. Not for them the delusion, common to other manufacturers, that EVs are ready for prime-time consumers. But it is, just like its gasoline-fueled mainstream counterpart, barrels of fun.

But it's not just the prepubescent, look-at-me paint job that catches your eye. Beneath that dissonant skin, there's some wildly impressive performance statistics that do nothing to shame the SLS's already-formidable reputation. The four onboard 400-volt electric motors (one for each wheel working through individual, fixed-gear 5.5:1 transmissions), for instance, generate 533 horsepower and 650 pound-feet of torque, an unusual combination of power and torque for an electric vehicle (most EVs, like diesels, produce lots of torque but correspondingly little in the way of horsepower). It's all made possible by the high-revving nature - 12,000 rpm - of the Mercedes motors. They accelerate the E-Cell, claims AMG, to 100kph in a scant four seconds - just 0.2 seconds slower than the petrol-fed car - despite weighing some 300kg more than the stock SLS. Indeed, a sense of unrelenting acceleration permeates the electrified SLS. Unlike the Tesla Roadster, which can boast nearly the same breathtaking acceleration to 100 klicks, the E-Cell doesn't "run out of breath" at higher speeds, sprinting to the 160kph (the most I was permitted in this test), relentlessly punching through the air on its way to a top speed that Mercedes says is well over 250 kilometres an hour. That's if it is in its "Sport+" or "Manual" modes. This being a German car and German engineers loving their gadgetry, there is a knob on board that allows the four electric motors to be limited to 40, 60 or 100 per cent of their maximum output. The base "Comfort" mode's 40 per cent limitation, for instance, is the equivalent of a conventional car's consumption-reducing "eco" mode, extending the SLS's range. "Sport" allows 60 per cent of maximum throttle for extended range on the highway while both "Sport+" and "Manual" offer full warp engines. It's a well thought out system that covers parameters such as the basic amount of regenerative braking and the immediacy of the throttle response. Where it all gets a little complicated is that the system also lets the driver alter the amount of regenerative braking. Unable to ignore the steering wheel paddles that the stock SLS uses for quick-shifting the double-clutch transmission, the gearheads from Affalterbach programmed four separate levels of regen accessible via those paddles. The problem is that it's nigh on useless (no one is going to alter the amount of regenerative braking for every corner) and unnecessarily complicated (certain levels of stronger regeneration aren't allowed until the battery pack has depleted a specific amount). Specific levels of regen programmed into the E-Cell's four basic modes would have been a better solution. It's not easy building an electric car out of an existing model (just ask Tesla). Luckily, the SLS's basic framework seemed ideally suited to electrification. Of the gullwing's basic structure, only the front suspension is changed - to accommodate the front-drive axle and motors - going from a classic double wishbone to a multi-link setup with a race-car-like rocker-arm actuation and horizontally mounted dampers. And, in a further attempt to minimise changes to the chassis, the E-Cell's 48 kW-h of Li-ion batteries have been divided up into three parts tucked in various nooks and crannies, such as the recess left by the absence of a fuel tank. That doesn't mean the SLS's handling is unaffected by its electrification, however. After all, those large batteries push the weight up by some 300kg (the batteries' all-up weight of 450kg is somewhat offset by the loss of the stock 6.2L V8 and its seven-speed transmission). In addition, placing the four rather hefty electric motors at the front and rear axles has futzed with the gullwing's polar moment of inertia. Worse yet, the steering box is a carryover from the S400 hybrid. The result is steering that is both uncommunicative and heavy that is further "blessed" with very little on-centre feel. It's a bit like driving an Xbox console on a real road; curves are handled easily but, like a recalcitrant recidivist fresh from the "yard", the E-Cell tends to wander when on the straight and narrow. Much will be improved as prototyping continues. AMG engineers will certainly work out the wonky steering and the suspension calibration is already spot-on. Performance - either speed or handling - will not be the SLS E-Cell's issue. As for the perennial EV bugaboo, range, AMG claims the electrified SLS can travel 150km between plug-ins. However, I used about 60 per cent of the battery's available energy (Mercedes allows its battery to be discharged to 10 per cent and charged to 95 per cent of its maximum 48 kilowatt-hour capacity) in just 67km, indicating a maximum range of just under 120km. And, yes, we had to sit around for a couple of hours while the batteries were juiced up before going home. In fact, it's also worth noting that, with 48kW-h of battery on board, it can take some time to replenish all those errant electrons. On Europe's 220V circuits, a full charge would take eight hours, while even when feeding from a high-tech (read expensive) 400V recharger it takes a full hour. At least AMG is realistic about the E-Cell's intent. It is, like all AMG's products, says Pietro Zollino, AMG's global communications public relations manager, "a fun car" meant to showcase the company's talents but also shows that, in the future, "performance and responsibility" need not be mutually exclusive. Not for them the delusion, common to other manufacturers, that EVs are ready for prime-time consumers. But it is, just like its petrol-fuelled, mainstream counterpart, barrels of fun. [e-mail]