Very seldom do auto companies make giant strides in fuel economy through the use of single technologies. More often, it’s the result of small savings here and there, which all add up – including “smart” alternator technology used by companies such as Hyundai.


The car’s alternator generates electricity to recharge the battery while the engine is running. The shaft that spins inside the alternator to make electricity runs off the car’s engine, requiring some of its power. The alternator’s shaft is always turning, but it draws more engine power when it is required to charge the battery, which can happen when accessories such as lights, wipers or the stereo drain it.


“The battery is constantly losing energy to feed these systems, and when it gets low enough, it says, ‘I need more energy,’ and the alternator feeds the battery,” says John Juriga, director of powertrain at the Hyundai Kia America Technical Center in Detroit, Michigan. “With a smart alternator, there’s a constant check as to what the battery voltage is.”


Unlike a conventional system, the smart alternator selects the best time to recharge the battery, such as during deceleration. When the driver is accelerating, and if the battery doesn’t need to be charged immediately, the smart alternator holds off. “You want that energy to go to the wheels, to move the vehicle forward,” Juriga says.


The smart alternator itself contains some electronics, but the system primarily depends on the engine control module, which determines the battery’s charge, the vehicle’s speed, and if the car is decelerating.

“If the battery voltage was below the minimum threshold, it would still charge the battery during acceleration,” Juriga says.

“You’d lose a little performance, but the battery takes priority and that’s why it’s ‘smart.’ It can decide when it makes the most sense to charge the battery, rather than just being ignorant of how the vehicle is operating. They’re small numbers (in fuel savings), but everything counts.”