42-Volt Electrical System Is Needed To Meet Future Vehicle Needs, GM Finds.

Power demands of vehicles for 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 that looks most promising is 42 volts. General Motors has been actively pursuing higher voltage research and applications.

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."