Plug-in electric cars are slowly becoming more common, but internal-combustion engines will remain a significant presence on the world's roads for decades to come yet.

That means automakers will continue trying to squeeze ever-greater efficiency out of these engines, making them more complex in the process.

This will almost certainly include a degree of electrification that falls short of full hybrid powertrains.

DON'T MISS: 48-volt mild hybrid systems: what they do, how they change the car

One option—often discussed by suppliers marketing such systems—is a more aggressive engine start-stop system, teamed with a 48-volt electrical system.

Many new cars are already equipped with start-stop systems, which shut off the engine while the car is stationary.

But a more robust 48-volt electrical system could allow this feature to be used more often, and could help provide supplementary power for accessories, proponents note.

Bosch 48-volt mild hybrid

Bosch 48-volt mild hybrid

Because these setups are less complex than full hybrid powertrains, they could provide some fuel-economy benefit at a lower cost to manufacturers.

A 48-volt mild or micro hybrid is estimated to provide 70 percent of the benefit of a conventional hybrid, 30 percent of the cost," said Sam Abuelsamid, senior research analyst with Navigant Research.

It could also boost the electrical power available in a vehicle from 2.5 kilowatts to 10 kW, Abuelsamid said.

MORE: Jeep Wrangler Diesel To Come Well Before Wrangler Hybrid

Electrical output is becoming increasingly important as automakers add more and more infotainment and convenience to their cars—all powered by electricity.

Navigant expects sales of start-stop equipped vehicles to grow from less than 25 million in 2016 to 61 million in 2025.

Current start-stop systems—not linked to 48-volt electrical systems—cost an average $300 and can improve fuel economy by 4 to 5 percent, according to The Detroit News.

2016 GMC Sierra 1500 eAssist

2016 GMC Sierra 1500 eAssist

Tightening emissions standards are often cited as the impetus for increased use of start-stop systems, but systems that can turned off are not used in EPA fuel-economy tests.

However, General Motors has begun selling cars with start-stop systems that can't be turned off, according to The Detroit News.

The Detroit automaker has a checkered history with more conventional mild hybrids, having offered two previous generations of mild-hybrid models that proved unsuccessful.

It recently returned to the concept with eAssist mild-hybrid versions of the Chevrolet Silverado and GMC Sierra full-size pickup trucks, although without 48-volt electrical systems.

GM's plans are also fairly small scale, with 500 Silverados and 200 Sierras to be built during 2016 and the option continuing for the 2017 model year.

Fiat Chrysler Automobiles (FCA) is expected to offer a 48-volt mild-hybrid system on its Ram 1500 full-size pickup and Jeep Wrangler.


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