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A new generation of “mild hybrids” is expected to drive into the United States as automakers attempt to meet ambitious 2017-2025 federal fuel economy standards.

The vehicles feature so-called “48-volt” systems that can improve efficiency of fuel-saving technologies such as regenerative braking and stop-start systems, which shuts off the engine at a stop sign or red light to save fuel.

The 48-volt systems add about $1,000-$2,000 to the cost of a car with a traditional 12-volt battery system. But they offer upward of 70 percent of the benefits of full hybrid systems that can cost thousands more.

The systems rely on three main components: 1. An electric motor/generator that can run as an electric generator to assist performance while acting as a traditional alternator to distribute power. 2. A larger 48-volt battery that can store more energy to power the increasing number of electric components. 3. An electric supercharger.

In real terms, these systems improve off-the-line performance after a start-stop system shuts off an engine at a traffic light. The supercharger helps eliminate “turbo lag” in turbocharged engines. And they generally increase efficiency and assist in regenerative braking systems that generate power while braking.

“To me, 48-volt is going to be a very important technology moving forward. It should be one of those fundamental technologies that should be adopted by all gasoline vehicles in the future,” Michael J. O’Brien, Hyundai vice president of corporate and product planning, told The Detroit News on the sidelines of a recent conference in Dearborn.

Hyundai has not announced plans for cars with 48-volt systems, but it is something the automaker is “looking at very actively,” O’Brien said.

Industry forecaster IHS Automotive expects sales of the systems to expand from virtually nothing today to 13.5 million by 2025.

“We are predicting this to take off exponentially after 2020,” said Christian Müller, IHS Automotive Europe component forecaster and analyst. “We’re looking at about 2.7 million in 2020, so you can really see sort of the exponential take-up there.”

The growth is expected as a result of automakers attempting to meet the Corporate Average Fuel Economy (CAFE) standards of 54.5 miles per gallon by 2025. Although the systems aren’t expected to achieve that much, they are seen as a low-cost, interim solution.

General Motors Co. and others have used functions of a mild-hybrid system, but not with a full 48-volt system.

The Detroit-based automaker debuted its mild-hybrid eAssist system on the 2012 Buick Lacrosse. The system has stop-start engine capability and a 115-volt lithium-ion battery to power a small electric motor-generator. Battery-assist boosts acceleration and improves fuel economy. The lithium-ion battery is recharged through power generated anytime the driver is coasting or stepping on the brakes.

GM currently uses the eAssist system on some full-size pickups.

Fiat Chrysler Automobiles NV CEO earlier this year said the company will premiere mild-hybrid technology on the 2018 Ram pickup.

Auto suppliers, including Valeo and Delphi Automotive PLC, are viewed as leaders in developing the technology.

“This is really a low-cost solution,” said Matti Vint, Valeo’s engineering director of North American systems. “It’s a third of the cost of a regular hybrid, but it still comes up with 50 percent to 60 percent of the benefits.”

The system does not replace a car’s traditional 12-volt electrical architecture or battery. The system simply helps provide efficiency and power to other vehicle systems such as an electric supercharger. It can be used on gasoline or diesel engine systems.

Audi’s SQ7 SUV is the first vehicle to feature Valeo’s 48-volt system and electric turbocharger. It is currently on sale in Europe.

Delphi’s system is similar to Valeo’s, but each can be tailored with different software, architecture and other components that can be changed depending on what automakers’ demands.

“A mild hybrid is not the main source of propulsion or what drives the vehicle, it’s just really a little bit of extra aid to the engine to give it a rest,” said Mary Gustanski, Delphi’s vice president of engineering and program management. “It provides a little assistance to that engine and gets you some better fuel economy, meanwhile giving you more power.”

Delphi is working with two global automakers and could see production within 18 months.

Valeo’s 48V system also can be coupled with a new “extended start-stop” system that the company is developing. The “extended” system will turn a vehicle’s engine off when approaching a stop or while cruising at a consistent speed. It saves more fuel than a traditional system that turns off the vehicle when it comes to a complete stop.

“It saves a lot in real-world driving,” Vint said, adding the company is working with a number of automakers on implementing the technology on future vehicles.

mwayland@detroitnews.com

(313) 222-2504

Twitter: @MikeWayland

Detroit News Staff Writer Michael Martinez contributed.

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