Management & Operations

Expect 42-volt systems to produce advantages and challenges

Posted on May 1, 2001 by Cliff Henke, former associate publisher/editor of METRO

Already being developed for cars and light trucks, 42-volt electrical systems will soon come to heavier vehicles, automotive experts say. They will first migrate to heavy trucks and then reach the passenger market, probably within the next five years, says Halsey King, a maintenance and technology consultant who is also a member of the Society of Automotive Engineers (SAE) Truck and Bus Council’s board of directors. King made his remarks at METRO Magazine’s recent Bus Technology Conference in Anaheim, Calif. When the systems arrive, they will dramatically improve bus electrical safety and operating performance, he predicted. However, like all new technologies in the transit market, 42-volt systems will greatly affect maintenance personnel. Marriage of convenience Through years of meetings in various SAE standards committees, the automotive industry has reached agreement on standards that will triple existing vehicle voltage for both battery output (12 volts to 36 volts) and generator output (14-volt to 42-volt). It’s a move that’s both dramatic and far-reaching, affecting virtually every area of vehicle supply, assembly, component design and manufacture. One such device enabled by the 42-volt system is something called an integrated starter-alternator (ISA). The ISA is basically what it sounds like: a device that performs the functions of starting the engine and generating juice for other onboard systems. The ISA unit is mounted directly on the crankshaft. It functions initially as a starter as the engine is ignited and then automatically switches over to alternator mode. It can support a variety of functions and technologies, including virtual “stop-and-go” power, which are particularly well suited to transit bus applications. With the ISA, there is no need to idle the engine. The engine can be shut off each time the vehicle stops and can be started when the vehicle needs to move. That will result in dramatically reduced emissions due to increased engine speed during starting. Other benefits include instantaneous starting (eliminating a not insignificant part of bus operators’ shifts at many transit properties), high electrical power to cope with ever-increasing loads from the growing list of onboard equipment, potential improvement of fuel consumption, high efficiency and minimal space requirements. With weight-saving, enhanced vehicle performance, emission reduction and improved fuel consumption, 42-volt electrical systems are the future. Dudley Wass, strategic business unit director for Visteon Corp.’s Electrical Conversion Systems, says that vehicle R&D changes due to the move to 42-volt technology will be sweeping. “The move to 42-volt entails a major redesign and re-think by OEMs as it encompasses everything from light bulbs to total integrated systems,” Wass says. A number of areas that will gain from the introduction of 42-volt technology include: better power steering, electrically operated brakes and suspension systems, more efficient water pumps, pre-heated exhaust catalysts and fully electric air conditioning. Expect shop adjustments These profound changes will most certainly affect the shop floor in an equally dramatic way. “Forty-two volt systems will totally rewrite preventive maintenance programs,” King says. “For one thing, they will probably reduce the list of PM procedures to a single sheet of paper—and that list will get shorter and shorter as vehicle systems are revised to take advantage of 42 volts.” King worries that the huge promise of 42 volts in future new buses will turn into a curse as the buses get older—unless shop floor personnel are properly recruited and trained. That message, he says, must be heard all the way to transit agencies’ executive suites and boardrooms—possibly even in the halls of Congress as it debates the industry’s funding levels.

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