DETROIT-A technological revolution is under way in the automotive industry as engineers globally have begun to develop 42-volt electrical systems to replace the current 14-volt systems in vehicles.
What's causing this switch?
The surge of new technology in cars is pushing auto makers to abandon the 14-volt standard-a move that is expected to free designers from many space constraints as well as help reduce automobile pollution.
European car makers-BMW, Mercedes and Renault S.A. for example-are likely to be the first to introduce 42-volt direct-current electrical systems.
But U.S. manufacturers won't be far behind. General Motors Corp. is planning to introduce Flex-Power, its first production-intent hybrid powertrain-an electric motor in GM trucks that won't power a vehicle at low speeds but will be used to restart a gasoline engine, which will shut off at stoplights instead of idling. The motor generates 42 volts of electricity and, GM said, has the ability to power many appliances in a house in the event of a power failure. The 42-volt system runs an electric pump in the power steering system and will be one of the first uses of a 42-volt system in autos.
Meanwhile, Ford said it would, by calendar 2004, offer a 42-volt Explorer sport-utility vehicle powered by a V-6 gasoline engine that features an integrated starter-generator.
The 42-volt system starts with the wiring harness. Low-voltage electricity must flow at a high amperage to operate a vehicle's accessories. That requires thick cables and wiring harnesses.
New electric systems also could eliminate dozens of mechanical drives from the engine compartment. Just packing the accessories around the engine is a design problem. Running the pumps electrically would free designers from many constraints.
Inside the engine, electro-mechanical valves could eliminate camshafts and timing chains. Auto makers also could improve fuel economy and engine emissions by integrating the valve cycles in the engine control computer.
Current 14-volt batteries generate about three kilowatts of power-barely enough to handle all necessary tasks. Adding to the burden are ``intelligent vehicle'' options such as adaptive cruise control, entertainment systems and onboard navigators.
Andrew Brown Jr., Delphi Automotive Systems director of engineering, said current 14-volt power generation systems on vehicles ``are pretty much tapped out.''
At the Robert Bosch GmbH division that makes alternators and starters, Michael Duemeland called the shift to a 42-volt system a rare opportunity for the industry to unify system design. ``It is a big step to new, innovative technologies.''
He believes 42-volt systems eventually could speed the development of hybrid-powered vehicles that use electric motors to supplement diesel or gasoline engines while helping reduce vehicle weight.
Long time coming
The auto industry was lucky the last time it boosted voltage in car electrical systems.
That was in the late 1950s, when the challenge of starting large, high-compression engines led engineers to push from existing 6-volt technology to the 14-volt charging system and 12-volt battery.
Unknowingly, the industry dodged a bullet in making the switch. Current flow below 15 volts is just under the threshold for persistent arc discharge. Sparking between electrical contacts occurs in a 14/12-volt system, but the arcing is unstable and is broken easily.
Boost the voltage to the emerging standard of 42 volts for charging (with a 36-volt battery), though, and what you get is an effect like a series of small welder's arcs.
The effect between connectors can generate temperatures above 1,832 degrees Fahrenheit. Connectors that vibrate loose can create the effect; so can a car owner accidentally disconnecting a live wire or a faulty switch.
The size of the connector doesn't matter. What does matter is the space between charged surfaces and how the contacts pull apart.
Almost all switches experience a small bounce as they bring electrical contacts together, and the result is like a car constantly trying to strike its own match. It is one of the biggest challenges to the higher voltage car.
Need for new connectors?
``The auto industry is going to have to face up to this,'' said Thomas Keim, director of the Massachusetts Institute of Technology consortium, a global leader in setting 42-volt standards.
Mr. Keim, who addressed a symposium earlier this year at the SAE 2001 World Congress in Detroit, said aviation has dealt with this kind of arcing for years, and only stringent, intensive maintenance has helped prevent electrical fires. Most vehicles don't receive that kind of maintenance, and mechanics agree that car wiring harness problems are notoriously difficult to repair.
It may take a new connector system in the car to handle electricity safely, at least on the high-power circuits that drive 42-volt features.
Researchers from the Fujikura Ltd. Automotive Products Division in Japan have posed a partial solution. Fujikura's Koji Sakiyama said researchers installed permanent magnets in either side of a 42-volt plastic wiring harness connector. The magnets create a field that electrical arcs must go around, making them longer and easier to break off, within 40 to 80 milliseconds. Mr. Sakiyama urged development of a global standard for safe disconnects.
Challenge for switch makers
Switch makers, meanwhile, are facing many instrument panel challenges that change the way electricity flows. At lower voltages, switches often carry the actual current used to drive devices in the car. Higher voltage switching will rely instead on indirect, low-voltage controls that may actuate remote power-handling solenoids, similar to that of a car's current ignition switch.
Suppliers also are reinventing the automotive fuse box, introducing smart fuses and computer-controlled switches to handle the loads imposed by 42 volts.
The simple replacement cartridge fuse likely will be a thing of the past for high-voltage electronics systems.
Six cylinders may be key
Six-cylinder engines may be the cutoff point between using a bolt-on stop-start alternator or an engine-changing integrated starter generator.
Bigger engines need more cranking power than the external alternator systems can provide, said engineers for Mannesmann Sachs A.G.
The supplier displayed a 90-percent efficient integrated starter generator at the SAE World Congress. Martin Sattler, supervisor for production of electric drive systems, said Sachs is supplying production versions of its starter-generator to luxury vehicle manufacturers in Europe, and is in talks with a North American luxury vehicle producer. Mr. Sattler would not name the manufacturers in either case, but said European agreements are in place and high-volume production of the starter-generator is expected in 2004.
``It is a problem to use a belt-driven starter generator with large engines,'' Mr. Sattler said. ``I do not think it is possible to start a six-cylinder engine, under cold conditions, with a belt-drive machine.''
Delphi Automotive Systems and Visteon Corp., have introduced concept starting systems that would use a belt-drive inductive starter-generator in place of the current alternator on cars-but not for traction uses.
Delphi Research Labs engineer Rassem Henry, addressing an SAE technical session, said such starter generators require less engineering disturbance because they fit in existing space at the front of the engine, while the serpentine belt drive they use is comparable to reliable, existing technology.
Delphi experiments found that the water-cooled 42-volt machine can produce up to about 3.4 kilowatts of power in a steady state.
Near-future cars are expected to demand just about that level of power, considerably higher than today's 14-volt systems. Many engineers, though, predict that cars will soon demand more than 8 kilowatts of power.
This story was compiled from information reported in Automotive News, a sister publication of Tire Business.