2018 Audi A8 to Feature 48-Volt Hybrid System

Despite the advancements in lithium-ion chemistry that makes these battery cells smaller, lighter, and more power-dense, the lead-acid box that at times strands you before a job interview is not leaving your car. Not even in the two thousand eighteen Audi A8, which features a 48-volt electrical system.

Similar to the systems found in the SQ7 TDI, Porsche Panamera, and Bentley Bentayga, the fresh A8 employs both 12-volt and 48-volt systems connected by a DC-DC inverter, only their operation is essentially reversed in the A8’s application. Here, the 12-volt system is the subsystem; powered by a conventional battery, it runs lighter-load accessories such as the lighting, stereo, and interior power outlets. It’s the primary 48-volt system that gives the car some hybrid functionality.

In principle, a hybrid like the A8 is old news. General Motors has continued refining its setup, called eAssist, since 2006. A secondary high-voltage battery powers a belt-driven motor-generator linked to the engine, which substitutes the traditional alternator and acts as a starter when the engine is warm. Honda’s now-defunct Integrated Motor Assist, very first seen on the one thousand nine hundred ninety nine Insight, put an electrical machine in the place of a torque converter. Neither of those systems could propel a car on electric current alone. Instead of a split-power hybrid as in the Toyota Prius, where a traction motor coupled to the transmission can drive the wheels on utter electrical power or in tandem with a gasoline engine, hybrids like the eAssist or this A8 can only reduce the engine’s workload under acceleration and very light geysers, such as a rolling begin. They also help run the vehicle’s 12-volt accessories and permit the engine to shut down when coasting with some light regenerative braking.

But the A8 advances this proven technology. A petite 48-volt lithium-ion battery (harshly the same size as the car’s 12-volt battery) powers a water-cooled, belt-driven motor-generator that substitutes a conventional alternator (like GM’s eAssist). As in the SQ7 TDI, a conventional 12-volt starter motor is still on board, but thanks to higher voltage, Audi says the A8’s belt-driven machine lets the engine embark quicker and more slickly. When coasting inbetween thirty four and ninety nine mph, the engine shuts off for up to forty seconds. The system also activates the stop-start feature more aggressively when rolling at speeds below fourteen mph. Audi won’t say how much its 48-volt system contributes to fuel economy and power improvements other that it can save seven-tenths of a liter for every one hundred kilometers. In American, that’s one gallon of gas over three hundred thirty six miles. GM’s latest LaCrosse eAssist increases city and highway fuel economy by four mpg versus the standard car, no puny figure. Together with a lighter curb weight, the next A8 also should produce higher EPA figures.

Gratefully, this hybrid setup doesn’t seem to sap any spectacle required of a $90,000-plus sedan. The 48-volt hybrid is slated for all A8 variants, the W-12 included. (That’s in stark contrast to the last A8 hybrid sold in China and Europe, which went front-drive and was saddled with a feeble four-cylinder engine.) Future four-cylinder Audi models will use the A8’s hybrid setup on a 12-volt scale, with less awesome coasting and fuel-saving results but a lower manufacturing cost. Eventually, Audi plans to put 48-volt primary systems into every car it makes. Before that happens, secondary 48-volt systems will begin running stereos, window heating, and various pumps and compressors as fresh models and refreshes arrive. The company, however, admits that electronic control units and lights will stick to 12-volt power for “well into the future.”

Perhaps even better than high-speed coasting is an auto stop-start system that relies on the car’s forward cameras and sensors to time engine shutoffs with greater—and possibly safer—precision. How often has a modern car shut off and restarted its engine numerous times in stop-and-go traffic, or shut the engine off in critical situations, like when waiting to make a left turn in busy traffic? The fresh A8 will be able to recognize traffic lights and take into consideration the car’s surroundings, such as when the driver is coasting to a line of stopped cars at a light that just turned green. If the driver releases the brake while coasting and there is a gap in traffic, the engine fires to life. While stopped, the engine will restart once the car recognizes the car ahead has begun to stir. If the A8 driver tailgates, the motor-generator underhood performs subtle regenerative braking.

Look for more details of this 48-volt hybrid system when the fresh A8 officially bows on July eleven after making a cameo in Spider-Man: Homecoming, out June 28th.

Related movie: