[size=medium]Goodbye, 12-volts
48-volt electric systems will handle connectivity, hybridization and autonomous driving
Richard Truett
With fuel economy regulations tightening and connectivity and autonomous-driving capability proliferating, the old-fashioned 12-volt automobile electrical system has reached the end of the road. That’s the view of Mary Gustanski, Delphi Automotive’s vice president of engineering and program management. And I agree.
Gustanski is charged with looking into the future and developing electrical architectures that will have to support:
• All the components for autonomous driving -- cameras, radar, lidar sensors, computers, etc.
• A greater array of drivetrain components, such as the oil and water pumps, that will switch from mechanical to electrical power.
• An assortment of hybrid-drive parts that will propel the car under electric power.
• More computing power that will improve vehicles’ connectivity, not just to the Internet, but to other vehicles and buildings, traffic signals and other structures in the environment.
During a visit to Delphi’s North American engineering campus north of Detroit, I chatted with Gustanski on the changes coming to electrical systems. It isn’t clear yet how elevating 48-volt capability to handle some of a vehicle’s electricity-guzzling components will affect costs at the automaker and consumer levels. But it won’t be cheap. Delphi estimates that adding 48-volt capability could cost around $1,200. But that seems low to me.
It’s no longer a question of the technology being fully baked. It is. Delphi engineers let me test drive a European 2016 Honda Civic diesel they converted to 48-volt power. The trunk contains a compact 48-volt lithium ion battery and a power converter. Under the hood, Delphi engineers installed a beefy belt-alternator stop-start system, an electric turbocharger and a few other components.
In early testing, the car’s fuel economy improvement is averaging about 10 percent. That’s huge. Engineers struggle to wring out even a 1 percent gain. But the Civic test mule’s higher fuel economy does not come at the expense of performance. The electric turbocharger not only eliminates traditional low-end diesel turbo lag (the pause in acceleration as the turbocharger impeller reaches high rpm), but it enables the engine to pull strongly at low rpms.
I drove the car around Delphi’s Troy, Mich., engineering center for about 45 minutes, testing not just acceleration, but the stop-start system and the car’s overall refinement. It’s clear that 48-volt systems offer significant advantages over today’s 12-volt electrical architectures. The Honda diesel engine has a 16:1 compression ratio, which makes it difficult to engineer a 12-volt stop-start system that is smooth and lightning fast. The Delphi system was nearly seamless.
Gustanski believes hybridization and the electrification of energy-hungry components will be essential for most automakers to meet tighter fuel economy standards. By 2025, automakers must achieve a fleet average 54.5 mpg. But credits for such things as environmentally friendly air conditioners and stop-start systems means that the actual fuel economy rating on the window sticker will be less than 54.5 mpg in nine years, and vehicles still will meet the government’s mandates.
But, generally, full-line automakers -- General Motors, Ford, Fiat Chrysler Automobiles -- that are heavily dependent on sales of pickups and SUVs have to improve their fuel economy by as much as 5 percent each year to meet the standard. Today’s electrical architectures are not going to be robust enough to carry the workload. Gustanski says the move to downsize and downspeed engines also has reduced the amount of power available for the ever-increasing electrical load. “Automakers have backed themselves in to the most effective and efficient engines ever, yet the pull for features and functionality is at its highest,” she said.
Not every electrical component will switch to 48-volt. Lights, radios, electric windows and door locks, for example, would stay 12-volt. And Delphi’s vision is that vehicles with 48-volt systems would also have a strong regenerative braking system to capture much of the energy lost when a vehicle slows down.
Around the turn of the last century, it looked like the 12-volt electrical system was at the end of its life, but engineers developed a new generation of alternators that amped up power output. LED lights actually reduced electrical demand. But now, with the electrification of the powertrain, with the components for autonomous driving already being installed and with connectivity increasing, 48-volt’s time appears to have arrived. “Electrical architecture is not just about getting the voltage, getting everything powered and getting the signals going, it’s about the data speed,” says Gustanski. “It’s about the computing power and how you lay out the electrical system.” Today’s cars, Gustanski says, process data at about 65 megabits, or 15,000 pieces of data, per second. “Tomorrow, it’s 1.5 gigabits,” she says, “or 100,000 pieces of data every time you blink your eyes.”[/size]
