Of all the components attached to the engine, none has been asked to carry a bigger load year after year than the alternator.
As electronics take over a greater number of mechanical functions, the performance of the alternator, the device that produces electricity to power accessories at engine speeds as low as idle, will become even more critical.
Consider: The average car in 1960 - the year Chrysler Corp. introduced the alternator on passenger cars - didn't have much in the way of electrical accessories.
The alternator powered the engine, lights, radio, heater motor and wipers. The alternator needed to generate about 30 amps to keep everything running smoothly.
Some of today's vehicles are outfitted with electric power steering, DVD players, mega-watt stereos, computerized front and rear air conditioning systems, high-performance lighting systems, electric window defrosters, heated and cooled power seats, sunroofs, electric engine fans, and electric water pumps.
The alternator on a typical light vehicle puts out somewhere between 130 amps and 200 amps.
In the 1990s, engineers were concerned that cars would require so much electricity that the 12-volt electrical system used in cars since the 1950s would have to be replaced with a 42-volt system.
The flexible 12-volt
But the 12-volt alternator has proven flexible and adaptable.
Not only have engineers been able to figure out how to increase electrical output, they also have been able to more efficiently use the energy generated by the alternator.
Paul Nicastri, a Ford Motor Co. staff technical specialist in Dearborn, Mich., says power consumption is increasing about 5 percent annually as vehicles acquire more electrical items.
But the alternator has been able to cope in part because efficiency has been improved. Nicastri says engineers have created more efficient windings in the alternator. They also have reduced electrical current losses by lowering the resistance of the copper wiring inside the alternator and have used better steel. Nicastri also says that easier rolling bearings and more efficient fans have contributed to the alternator's improved performance.
Even though power consumption continues to increase, the industry isn't likely to switch to 42-volt systems anytime soon, says William Mattingly, a Chrysler group vice president.
"We keep figuring out ways to make 12-volts work," he says. "From a passenger-car standpoint (42-volts systems) are in the pretty distant future."
Alternators also have been adapted to work with gasoline-electric hybrids, such as the Toyota Prius, Honda Insight and Chevrolet and GMC hybrid trucks.
The reliability of the alternator has been improved despite the fact that it is under increased stress.
Master mechanic Larry Parry, who writes a syndicated newspaper column on car repair and owns The Magic Mechanic auto repair shop in Orlando, Fla., says it is not uncommon for an alternator to last 250,000 miles "Under normal circumstances just bearings and brushes will wear," he says.
Alternators began replacing generators in the 1960 model year on Chrysler Corp. passenger cars such as the Valiant compact.
Because alternators were cheaper to produce, produced more electricity and needed less maintenance, the technology caught on fast. The 1967 Triumph TR4-A sports car was one of the last to use a generator.
But alternators had been around since the 1940s. The Leece-Neville Co. of Cleveland, now a part of Prestolite Electric Inc., produced some of the first alternators.
The difference between an alternator and a generator is that a generator struggles to keep a battery charged at low speeds. Also, generators had to be geared to run at slower than the engine RPM because their internal parts tended to fly apart at RPMs higher than 5,000.
Today's alternators easily handle RPMs and higher loads, but they require bigger, fatter fan belts because of the strain they put on the engine under full load.