Mercedes Vision EQXX concept escapes EV weight spiral

Making the Vision EQXX a benchmark for electric vehicle efficiency meant avoiding a downward spiral.

It’s one of the main reasons Mercedes-Benz has stuck with the idea of ​​an air-cooled battery-powered Vision EQXX concept, and listening to project manager Malte Sievers, it’s one of key decision points of the project that allowed him to surpass his initial objective. : 1,000 km (621 miles) on a single charge, at real speeds.

“Putting the liquid cooling system in that battery would have triggered a sort of spiral – and you can see that with a lot of larger systems,” Sievers explained to Green Car Reports last week at Mercedes’ Immendingen proving ground before I was allowed to drive this part of the future (and the only one on Earth).

To sum up: liquid cooling would have added weight and increased the height of the battery. This would have increased the height of the vehicle in order to maintain interior space, which would have increased frontal area and affected aerodynamics. And this combined would increase the energy required and therefore the size of the battery needed.

As we’ve previously reported, the futuristic Vision EQXX is the most efficient car Mercedes-Benz has ever built, and in April the EQXX had a real-world run, covering a 746-mile trip from Stuttgart , in Germany, to Silverstone, England, on a single charge and with energy to spare for a few laps of honor.

The EQXX is by no means a production vehicle. It’s proof of how the automaker’s electric vehicles could be made more efficient – much more efficient – in the future.

As Sievers pointed out, the EQXX represents a holistic approach, ensuring that every element of the vehicle, including but not limited to the propulsion system, takes the simplest and most efficient route possible. .

“In order to achieve this car and make it the most efficient Mercedes we’ve ever built, you have to look at every element of the car that impacts efficiency, and that’s basically it,” he said. -he declares.

From the 20-inch forged magnesium rims and specially developed Bridgestone Turanza Eco tires specially developed for the EQXX, to the fiberglass-reinforced plastic for the doors and a mega-cast aluminum at the rear of the vehicle, with towers of damping, the EQXX is fighting for a different and more efficient future in every way.

And when I went back to find out more about cooling, Sievers quipped, smirking, “We really don’t.”

He makes a point. The EQXX battery contains carefully selected cells, arranged in such a way that they require nothing more than outside air. Occasionally.

Sievers said that at the proving grounds in the summer heat, the EQXX’s pack didn’t significantly exceed ambient temperatures – 86 degrees as we spoke, with a high of 99 predicted for this afternoon. He reported by remote sensing that the pack was currently at 90 degrees.

Regarding these cells, Sievers noted that due to improvements in internal resistance, the cells simply don’t heat up as much as they did in previous generations under load.

“It shows there’s a lot to be gained even by sticking with currently conventional chemistry,” he said, perhaps in a hint of what the automaker is planning for these future electric vehicles. “And it’s not just solid state; there are all kinds of new things coming.

The EQXX does not avoid cooling completely, however. There is water cooling for the electric drive unit and inverter, as well as an oil-to-water heat exchanger which helps cool the motor bearings. The flaps that open at the front of the vehicle only open when needed, allowing a thin layer of air to pass through the battery and these systems, dissipating heat.

Mercedes-AMG High Performance Powertrains, which works with Formula E and Formula 1, designed the inverter for the car, which operates on a “plus 900 volt system”. It incorporates many Formula E learnings and is a key part of how the overall efficiency of the electric drivetrain is 95% from cell to wheel. The inverter, Sievers said, looks “radically different from anything we’ve done so far.”

“Basically, we’re looking for every watt here,” said Julien Pillas, who worked specifically on the electric drive system.

Much of the development of the drive system for the EQXX, which began in 2020, was carried out on a vehicle dubbed Emma – for the next MMA platform, due around the middle of the decade with models at little close to the size of the Tesla Model 3 and Model Y, which will reap some of the benefits of the EQXX project. Emma weighs nearly 5,300 pounds with the EQXX’s roughly 100kWh air-cooled pack mounted below. That’s just a few hundred pounds more than the weight of the production EQB with its 70.5 kWh liquid-cooled block.

Thank the air-cooling again for the EQXX pack’s 1,089-pound weight and, by extension, its sub-3,900-pound total.

I have to take a ride to Emma first, on a closed course, to get a feel for the interface and calibration of the throttle and brakes, which are exactly the same as the EQXX (but with this additional mass). Part of that involved getting to grips with regenerative braking, which is much more aggressive than in Mercedes’ current EVs – keeping modes ranging from D- (moderate regen) to D+ (slip) but adding a ” D–” which allows one-pedal driving without holding the brake. Keeping the most efficient in the EQXX also meant keeping the throttle light and staying within a 25kW power band.

In the proving grounds teeming with engineers, of course they kept the telemetry on us. So I was able to check the efficiency – and much more – of my discs. On a loop of around 16 km (10 miles) covering a range of terrain and speeds of up to 100 km/h (62 mph) and an average of around 50 km/h (30 mph). I averaged 12.1 kwh/100 km (5.1 miles/kwh) at Emma, ​​which is almost double the efficiency I had seen on a country road loop in the US. ‘EQB earlier today.

This proved the value of the drive system. Now I headed for the real thing – the EQXX with its beautiful aerodynamic bodywork and 0.17 coefficient of drag. I slide into the mushroom-based vegan leather seats and pull the Biosteel fiber door strap, adjusting the seat, and I find it’s actually quite comfortable for my six-foot-six long legs.

The EQXX felt more perkier for sure, and I found myself driving faster than I did in the mule SUV, requiring constant speedometer attention to stay within the speed zones of the proving grounds. While I heard the whine of the drive systems and a bit of road noise, there was almost no wind noise—the reward of aero.

After a bit of fun after the efficiency loop, I had the chance to harness the 180kW (241hp) and check that the communicative steering and a very low center of mass make this quite a fun vehicle to drive rapidly.

And then, a final count. In the EQXX I averaged 8.39kwh/100km, or about 7.4 miles per kwh, or about 45% better than what I saw at Emma. Or about twice the distance with the same kwh that I would be able to cover in most relatively efficient electric vehicles today.

A curious piece of the EQXX efficiency puzzle is solar power. In the EQXX it only works in the 12 volt system, with no way for power to reach the traction battery. Maximum system power is around 600 watts, with the potential for the system to gain around 16 miles of range over an entire day.

Sievers admits that’s not necessarily the decision they’d make in a production model – like omitting the on-board charger – but for the EQXX and its range goals, it made the best sense and freed up the battery from traction for high voltage use – with occasional operation of a DC-DC converter when needed. In the EQXX, the heat pump is powered by the high-voltage system, but the rest of the climate control system, steering, control units, infotainment system, etc. all run on 12 volts.

Likewise, the EQXX was not designed for fast charging. Although its air-cooled pack can charge to a respectable 140kW without heat buildup, enough to gain 186 miles of range in 15 minutes.

“We’re not trying to show that fast charging is bad,” Sievers said. “In researching efficiency, we realized after fasting that it actually helps load up a bit – that’s the fun side of engineering, that we actually discover new things that we didn’t see coming. .”

While those with the project are hesitant to give more clues as to what exactly might go into production MMA electric vehicles, we’ll take that as one of the clues.

In some ways, the EQXX is the VW XL1 of this decade, as a hyper-efficient poster car. Although VW built the XL1 super mild diesel hybrid in very small numbers, much like the EQXX, it was designed as a technological stunner.

That said, having explained why the EQXX exists and drove it, I can say that while the EQXX won’t be produced, it means a whole lot more to help steer a generation of EVs away from this downward spiral.