42-Volt Electrical System Is Needed To Meet Future Vehicle Needs, GM Finds – Brief Article
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.”
A 42-volt vehicle would 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.
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.”
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