For Release: October 4, 2000

CONTACT:

Charles Licari
PHONE: 810-986-0077
E-MAIL: charles.licari@gm.com

WARREN, Mich. - We've all chuckled at Tim Allen's oft-repeated line in the TV show "Home Improvement": More Power! But electrical engineers at General Motors and throughout the global automotive industry are taking it very seriously.

The growing power demands of vehicles for "green" features like electric power steering and customer convenience features like electrically-heated windshields are quickly eating up the energy budget provided by a traditional 12-volt battery and generator. For vehicles to continue to improve to meet growing customer needs, electrical power must be increased. As it is, wires and semiconductor switches get unmanageably big. It takes a higher voltage to get them back down in size.

The industry standard being pursued is 42 volts. In the U.S., that number was selected by an industry-wide research consortium led by the Massachusetts Institute of Technology. In Europe, Forum Bordnetz chose the same voltage. It's not as odd as it may at first seem: 42 volts is three times the voltage of the system now in use, which operates at 14 volts when the vehicle is running. (The 12-volt battery becomes a 36-volt battery).

However, converting to 42 volts is much easier said than done, according to Dennis Wiese, GM program executive for 42-volt architecture. "To change voltages, everything from a vehicle's lighting to charging systems will have to be redesigned," Wiese said. "Wiring, connectors and relays all need to change, and you'll also need a new 36-volt battery for energy storage. Even service stations and dealerships will need new equipment."

Lydia Sobo, the GM advanced purchasing engineer working on the program, said the whole point of GM's program on 42-volt architecture is to find out the best way to do all this. "Part of the GM program's mission is to identify suppliers who are working on 42 volts and begin working with them," she said.

The key question on everyone's mind is: will vehicles be completely converted to 42 volts in one step, or will they go through a transition period where they have both 42 and 14 volts?

GM's EV1 was the first recent vehicle to use components in the 42-volt range, and the knowledge gained will be used on the GM 42-volt program. Wiese thinks the first 42-volt systems on conventional vehicles will appear within the next couple of years, but on a car or truck that has both 42 and 14 volts. That means two batteries and more weight and expense. "Dual voltage systems are inevitable, because suppliers are not ready with all the 42 volt components," he said.

"We are undergoing fundamental changes in vehicle electrical architecture and 42 volts will be a part of that, " Wiese said. "The new architecture will enable some exciting advancements." GM is leading the industry in telematics with systems like On-Star, and its researchers in chassis control and engine control have plenty of ideas for by-wire systems; it becomes a question of how to roll everything out in a cost-effective fashion, he said.

To meet future fuel-efficiency demands, for example, many vehicle engines would shut down instead of idling at traffic stops. A logical way to do this is with a 42-volt flywheel-alternator-starter that replaces traditional starters, belt-driven generators and flywheels. A single device mounted on the end of the engine's crankshaft works as a starter motor by spinning the crank at starting. A flywheel-alternator-starter is much quicker to reach ignition than current starters, and will enable the stop-and-start engine. The same device serves as a generator, charging the battery both directly from the engine, and during braking, allowing recovery of energy ordinarily dissipated in the brakes. This even reduces brake wear.

A 42-volt vehicle would also have lighter and smaller wiring because amperage decreases when voltage increases, according to Michael Matouka, a GM staff development engineer and member of the GM 42-volt program team. He is also GM's representative to the MIT 42-Volt Consortium. Also, switching semiconductors are expected to cost less as the amperage decreases, enabling more electronic controls and customer-desired features. However, many loads such as incandescent lights and computer circuits must stay at lower voltages, requiring changes in their power supplies, Matouka said.

There are many challenges with a higher voltage system, Matouka added. For one, the electrical relays throughout the vehicle's wiring either have to be redesigned or replaced with semiconductors. When a relay opens and closes at 14 volts, there's a slight arc. But at 42 volts, that arc becomes much more pronounced, and could pit the contacts and cause premature wear on the device. Arcing is also a concern when making or breaking connections such as during fuse or battery replacement. Another concern is jump starting 42-volt cars and trucks from those with 14 volts, and vice-versa.

GM is building test cars and trucks with 42-volt components, Wiese said. He added, however, that a lot of modeling and testing will be done on computer simulations to save time and expense.

"42-volt architecture is an industry opportunity, not just GM's," said Wiese. "We look forward to working with our industry colleagues to develop that opportunity. Of course, once 42 volts is out there, GM wants to be the first to take advantage of it."