Don’t go kindly on that good night, the cars should run and take care at the end of the day. Range, Range vs. Decaying Battery.
Yes, it’s a poor imitation of Dylan Thomas’ poem about getting old, but it’s a great metaphor for what Mercedes-Benz has just achieved with its highly streamlined all-electric Vision EQXX concept car. Offering another 87 miles of range still to go—something that didn’t run empty—this road-legal concept was able to run 11 hours and 32 minutes without stopping to charge its battery. On real roads and at real road speeds as I traveled from Sindelfingen, Germany, to Cassis in northern Italy. For those without a map of Europe, that translates to a total distance of 1,000 kilometers, or 621 miles, with an average speed of just over 54 miles per hour.
An epic journey of electric vehicle technology
The trip began on a cold, rainy morning in Sindelfingen. The goal, of course, was to run the EQXX on one more charge than any other electric car before. With Germany’s TUV – a certification body that works on everything from cars and their aftermarket parts to home electronics – coming in and checking for tampering at the charging port, the Mercedes and Vision EQXX set out on one incredible record-breaking journey. The achievement makes the EQXX, per Mercedes, the longest-running legal vehicle on the road to date, although we have to remind you again that although the EQXX is road-legal, you can’t buy exactly one, so it’s not technically a ‘production car’ “. “
While the first part of the EQXX race landed on the motorway at 87 mph, the rest of the driving involved driving through the Swiss Alps and the Gotthard Tunnel, normal street driving around Milan, and down to Cassis, Italy, via the road along the Cote d’Azur where EQXX ended late in the evening. For 11 hours and 32 minutes, the 621-mile endurance test will finish with an average speed of 54.43 mph. Even after nearly 12 hours of driving, the 8.7 kWh for every 62 miles of average EQXX consumption means it can still travel another 87 miles using the remaining power in the battery.
Even if you allocate 87 unused miles of range, the EQXX (which has not been and will not be EPA tested) breaks the official range numbers for the current champions in this arena, the Tesla Model S (405 miles) and Lucid Air (up to 520 miles per EPA). Working at 87 miles, the EQXX had the ability to go over 700 miles between charges. That would be an impressive range for an internal combustion car, not to mention an electric vehicle prototype.
It was also a demonstration of the high-energy, high-density silicon EQXX battery that is air-cooled rather than water-cooled. This means that despite being a 100 kWh battery pack, the package is 50 percent smaller and 30 percent lighter than the 108 kWh package in the Mercedes EQS. The battery measures 78 x 50 x 4 inches and weighs just 1,091 pounds. In order to keep the battery cool, the Vision EQXX uses permanent passive cooling with a cooling pad under the chassis. This battery gives an amazing power density of approximately 400W/L while allowing close to 900V at operating voltage.
While the battery is air-cooled, the 180 kW Formula 1 derived engine is not. However, the hydrocooling of the propulsion engine allowed Mercedes engineers to create an on-demand active cooling system that would open and close the shutters at the radiator vents as needed to keep the system cool. These shutters will also open when the air conditioning system needs intense cooling, so the cabin remains at a comfortable temperature while driving with minimal excess aerodynamic drag from the body vents.
On the other hand, the cabin heat is controlled by a heat pump that draws air sources from the heat exchanger and the drive system to regulate the temperature. It is powered and the entire 12V system is a solar roof made of 117 solar cells that reduce drag on the driving battery. It also uses its regenerative system during braking and during coasting to recover lost power while the entire drivetrain has been optimized to reduce losses by 44 percent over the standard electric vehicle powertrain.
The impressive EQXX range is also due to the use of lightweight materials. Most interesting is the use of aluminum disc brakes because the EQXX’s energy recovery system is strong enough to reduce the use of the hydraulic brake system. The rear floor also uses a new aluminum casting process that allows one part to be used on multiple parts that will add to its weight.
Moreover, anywhere the structure did not require additional strength, gaps were formed to reduce weight even more. While a metal plate is required to help passively cool the battery, the top of it is made of a new carbon fiber and sugar composite. Finally, the Vision EQXX weighs 3,869 pounds.
That weight is handled by a set of Bridgestone tires designed specifically for the Vision EQXX that have a rolling resistance of just 4.7 for the 185/65R20 tire. That’s significantly lower than the tires used in the EQS, which have a rolling resistance of 5.9. The lower resistance is achieved with new tire technology that reduces tire deformation while driving as well as a tire belt that is tighter than standard tires. Bridgestone not only reduces rolling resistance, but also reduces tire weight by 20 percent.
Air resistance is also a major detriment to high efficiency, which is why the EQXX features more than just the previously mentioned shutters. The transition from tire to rim is another part of the EQXX that has been aerodynamically optimized. The entire body is also sculpted to maximize aerodynamic efficiency and reduce drag for a CoD of 0.17 with maximum aerodynamic efficiency. That’s not bad for a vehicle with a front headroom of 22.82 square feet.
While the Vision EQXX is a one-off, the technologies built inside will all be carried over to the next all-electric vehicles from Mercedes-Benz. While aluminum disc brakes, high-silicon anode batteries, carbon-fiber composites and sugar may be out of full production, the use of aluminum one-piece structures, improved heat pumps and more efficient electric drivetrains are not. All along will lead to some impressive numbers in the upcoming electric cars from Mercedes.