The 42-Volt Challenge
In a popular song, folk singer Jimmy Buffet explains how "changes in latitude lead to changes in attitude." That may be true in the Caribbean paradise he often sings about, but it doesn’t apply to the U.S. auto industry.
Engineers in Detroit still sit at the same latitude and try to maintain a positive attitude in today’s cost-conscious environment. However, the traditional electrical system that powers vehicles is about to undergo a radical change.
Carmakers are starting to convert from 14-volt systems to a new 42-volt architecture. Ironically, Detroit is situated at a latitude of 42 degrees North.
The dramatic voltage increase is necessary to support power-hungry vehicles, improve overall fuel efficiency and reduce emissions. The transition to 42-volts will make it possible for engineers to eliminate nearly all of today’s inefficient mechanical and hydraulic systems. They will be replaced with new technology, such as integrated starter-generators, steer-by-wire systems, brake-by-wire systems, active suspension and electromagnetic engine valve systems.
"There are more revolutionary innovations waiting to debut on vehicles than any other time in our industry’s history, and 42-volt technology is the system that will help put many of these technologies on the road," claims Walter Fields, vice president of automotive engineering materials at DuPont Automotive (Troy, MI).
However, the new system will affect how alternators, connectors, motors, relays, starters, switches, terminals, wiring harnesses and other components are assembled and tested. "Higher voltage systems will have far-reaching effects on the automotive industry, from component design and manufacture to supply and assembly," says Dave Wright, director of advanced engineering at the Packard Electric Systems div. of Delphi Automotive Systems (Troy, MI).
During the last 30 years, the power requirement for vehicles has risen more than 50 percent. Today’s typical luxury vehicle has more than 3 miles of wiring, 2,000 terminals, 50 connectors, 1,500 electronic circuits and 100 electric motors. Every year, more and more cars are equipped with new features, such as cell phones, personal computers, satellite navigation systems and other onboard communication devices. The next wave of automotive electronics will require more power as they replace outdated mechanical systems.
The current 12-volt battery and 14-volt electrical system is being stretched to its power limits to run navigation systems, lighting, engine electronics and dozens of other applications. Indeed, the typical luxury vehicle demands up to 2.8 kilowatts of power, while the current 14-volt system only generates about 3 kilowatts of power. By comparison, 42-volt systems will provide 8 kilowatts of power.
"For vehicles to continue to meet growing customer needs, electrical power must be increased," says Dennis Wiese, program executive for 42-volt architecture at General Motors Corp. (Detroit). "As it is, wires and semiconductor switches get unmanageably big. It takes a high voltage to get them back down to size."
Why 42 Volts?Automotive engineers and suppliers began discussing higher-voltage systems more than 10 years ago, when they first noticed the difficulties associated with thick wiring bundles. Those problems grew as they added audio, video and cellular components.
The industrywide standard of 42-volts was selected several years ago by an automaker consortium led by the Massachusetts Institute of Technology (MIT, Cambridge, MA). The Consortium on Advanced Automotive Electrical/Electronic Systems and Components, which operates under the auspices of MIT’s Laboratory for Electromagnetic and Electronic Systems, is working to resolve challenges surrounding 42-volt systems.
According to Tom Keim, principal research engineer and director of the consortium, 42 volts is three Arial the voltage of the system now in use, which operates at 14 volts when the vehicle is running. Instead of the traditional 12-volt battery, the new system will operate with a 36-volt battery.
Keim says 42 volts is the threshold—anything higher presents safety concerns. Because 50 volts can stop a human heart, anything higher than that requires special safety systems to prevent contact with wiring. In addition, any voltage above 60 needs more heavily insulated wires and connectors that would add weight.
The auto industry has used 14-volt battery technology for more than 40 years. Automakers in the United States switched from 6- to 12-volt batteries in the late 1950s. General Motors led the charge to the 14-volt power system. It introduced the first 12-volt battery in 1955. European car companies were slower to adapt the technology, but finally made the big switch in the mid-1960s.
Because the auto industry has used 12-volt battery technology for more than 40 years, the switch to 42-volt systems is expected to create new challenges for manufacturing engineers.
Numerous BenefitsThe shift to a 42-volt standard will offer numerous benefits. For example, some devices that are now driven mechanically will be driven electrically, since the needed power will be available. Components such as air conditioning compressors, water pumps and power steering systems, will be operated only on demand, instead of remaining a continuous parasitic load on the engine when they are in the "off" part of their operating cycle. This feature will reduce fuel consumption and emissions.
Other benefits include:
- Higher efficiency electrical systems. Conventional alternators are designed to optimize current flow only at idle. A 42-volt integrated starter-alternator (ISA) will replace traditional starters, belt-driven generators and flywheels. Vehicle engines will shut down instead of idling at traffic stops. And an electric motor, rather than a belt to the engine’s crankshaft pulley, will drive the water pump, reducing load on the engine.
- Better components. A single device mounted on the end of the engine’s crankshaft will work as a starter motor by spinning the crank at starting. An ISA will reach ignition much faster than current starters, enabling the start-stop engine. The same device will serve as a generator, charging the battery both directly from the engine and during braking, allowing recovery of energy ordinarily dissipated in the brakes. This will help reduce brake wear.
- Improved fuel economy. The ability to add technologies, such as start-stop with an ISA, brake regeneration and torque boost, will improve fuel economy 10 percent to 15 percent.
- Reduced emissions. The internal combustion engine’s current slow start routine is where most hydrocarbons are emitted into the atmosphere. Because 42-volt systems will enable fast start-stop strategies, a high rpm start will eliminate the typical slow, rough start and reduce emissions.
- Reduced weight. Increasing the amount of current will allow for a 10 percent reduction in the overall weight of wiring by reducing the size of heavy gauge wire. Wiring harnesses will become lighter.
- Solid-state circuitry. The 42-volt technology will make it more cost effective to use advanced solid-state circuitry, which will allow for increased networking capabilities. Switching semiconductors, for instance, are expected to cost less as the amperage decreases, enabling more electronic controls and customer-desired features.
- Design flexibility. Components that have traditionally been clustered around the engine, such as heating and cooling systems, will be more evenly distributed around the vehicle, enabling sleeker, better balanced designs. There will be fewer belts and pulleys to contend with.
- New technologies. With the 42-volt system, technologies that were previously impractical or impossible will be feasible. Higher voltages will enable more effective and efficient use of drive-by-wire technologies, ride control systems, electronically heated catalysts and electromagnetic valve systems.
Transition PeriodCars equipped with 42-volt electrical systems were expected to be on U.S. roads by 2003. But, a longer than anticipated development time has pushed the technology off to a 2005 time frame.
"People were quick to figure out the benefits, but slower to look at the obstacles to making the transition successful," says MIT’s Keim. "I think it will be a slow transition period. It will probably take more than 10 years for the technology to become widespread." By 2010, the annual production of 42-volt vehicles worldwide is projected to be 13 million units.
But, some observers are skeptical of such predictions. "People in the auto industry are very reluctant to make big moves like this," claims Richard P. Bodine Jr., chairman of Bodine Test and Assembly Systems (Bridgeport, CT). He compares the transition from 14- to 42-volt electrical systems to another revolution that shook the auto industry 20 years ago: the switch from carburetors to fuel injectors.
However, Bodine says "it’s not a question of ‘if’; it’s when." That’s why American, European and Japanese automakers are busy testing cars and trucks equipped with high-voltage components.
"We should begin to see 42-volt technology on the road in the next 2 to 3 years," says Delphi’s Wright. "Widespread use is still somewhat uncertain, and could vary depending on various market factors, including fuel economy requirements."
Volume ramp up is expected to occur around 2007. Until then, car companies will be slowly introducing the technology in limited production, probably beginning with select 2004 model year vehicles.
According to Norman Traub, director of 42-volt initiatives at the Society of Automotive Engineers Inc. (Warrendale, PA), the first 42-volt vehicles will be marketed in countries with higher fuel costs and more congestion, such as Japan. In fact, Toyota Motor Co. (Tokyo) recently became the first automaker in the world to offer a hybrid 42-volt system as an option. Its Crown Royal Saloon—a luxury car only available in Japan—is 40 percent more fuel efficient than vehicles not fitted with the system.
The first cars to feature the new technology in the United States will be sport utility vehicles (SUVs) and light trucks. For instance, Ford Motor Co. (Dearborn, MI) plans to equip its popular Explorer model with a 42-volt system featuring an ISA. General Motors plans to offer a 42-volt architecture in a special pickup truck.
Hybrid SystemsTo ensure a smooth transition, electrical systems will not be completely converted to 42 volts in one giant step. Instead, the auto industry will go through a period when vehicles are equipped with both 14- and 42-volt architectures.
Traub says the dual 42/14-volt system is an interim step that is expected to be the norm for several years. Low-voltage devices, such as radios, will continue to use 14 volts. "Components that draw large amounts of energy and run more efficiently at higher power, such as seat heaters, will benefit from the 42-volt system," says Upton Bowden, a vehicle systems engineer at Visteon Corp. (Dearborn, MI). "It’s more economical."
Dual-volt systems will require two batteries: one traditional 12-volt unit and a 36-volt unit. The 36-volt battery will take current from a new generation of higher voltage alternators, while the 12-volt battery will recharge directly from the 36-volt unit.
"Dual-voltage systems are inevitable, because suppliers are not ready with all the 42-volt components," says GM’s Wiese. "It also becomes a question of how to roll everything out in a cost-effective fashion."
The dual-volt alternative gives suppliers time to develop 42-volt components. "The cost to convert to purely 42-volt would be cost-prohibitive right now," explains Bowden.
A gradual changeover minimizes the cost of simultaneously changing all vehicle systems to a new standard. Also, not all components benefit significantly from increased voltage, such as certain sensors and spark plugs. In fact, radios and incandescent lighting systems actually operate better at 12 volts.
The two-battery system presents short-term challenges, such as extra wiring, extra weight and added complexity. In addition, suppliers need time to develop a part identification system to distinguish between 14- and 42-volt components. Different sizes, colors and markings will probably be used.
"As vehicles complete the transition to a 42-volt system, the power and signal distribution architecture will be reconfigured to a single system," says Wright. "At that point, wire gauge will be reduced, wire bundle sizes will shrink, smaller connection systems will be utilized, and mass and cost will be substantially decreased. The installation and routing of the wiring system within the vehicle will be simplified, and new vehicle design opportunities will be realized."
Unique RequirementsAuto part suppliers are scrambling to develop components capable of meeting the unique requirements of 42-volt systems. All devices involved in power generation and energy storage are affected, such as battery packs, drive motors and power electronics.
"Material and components will need to significantly change to meet the new requirements," says William Hsu, DuPont’s technology vice president. For instance, upward shifts in heat-resistance and electrical-property requirements will place some new challenges on thermoplastics.
"Some existing polymers won’t work," claims Hsu. His company has developed a translucent grade of nylon to replace polyethersulfone (PES) in fuse applications.
According to Hsu, 42-volt vehicles will need more plastic gears to serve in electrically actuated systems. "Since 42-volt enables automakers to move belt-driven systems, like air conditioning units, out of the engine compartment, plastics that couldn’t stand underhood heat and mechanical loads might now compete against metal," he points out.
"Some 42-volt systems will bring plastic gears closer to the engine. And these gears will have to go beyond the standard domain of window lifters."
Safety and the threat of vehicle fires is an inherent concern for engineers working on 42-volt components. For example, batteries must be developed to account for reverse battery voltage and jump-starting at high voltages. Relay arcing is another problem that is being addressed by engineers. Higher power relays, switches and fuses need to be developed. Many devices must be redesigned or replaced with semiconductors.
When a relay opens and closes at 14 volts, there’s a slight arc. But, at 42 volts, the arc becomes much more pronounced. It could pit the contacts and cause premature wear on the device. Electrical arcing can generate temperatures up to 1,832 F, melt metal or burn plastic, and ignite fuel vapors.
Arcing also is a concern when making or breaking connections, such as during fuse or battery replacement. To address that challenge, relays and connectors must have wider spacing between contact points to allow for differences in electrical arc.
"Because of the added potential for arcing in 42-volt systems, the major impact on wiring assembly will be quality related," says Delphi’s Wright. "Ensuring that all terminals are correctly seated and locked will take on additional importance. In addition, sealed connectors will be more commonly used, increasing the number of components that a wiring assembly plant must deal with.
"More physical protection devices, such as clips, clamps and shields, may also be used. We are investigating the use of flame-retardant materials for 42-volt connectors because of concerns regarding arc containment and corrosion."
According to Visteon’s Bowden, many electrical parts and components will look similar whether they run on 14- or 42-volt systems. "They will generally be the same shape," he points out. However, the inside of motors, alternators and other devices will be noticeably different. For instance, more windings of finer-gauge wire will be used in coils.
A 42-volt vehicle will have lighter and smaller wiring, because amperage decreases when voltage increases. For instance, an electric motor that takes 12 amperes at 12 volts requires only 4 amperes at 36 volts. This will enable automotive suppliers to downsize wiring and shrink components.
Higher voltages will allow more effective and efficient use of thinner and lighter wiring. "More power can be transferred with smaller wires, cables and connectors," says Wright, "which reduce packaging sizes."
The tripling of voltage means the current carried by the wiring will shrink by two-thirds. That means smaller wires throughout the vehicle, and bigger and smarter fuses. "But, excellent electrical insulation and dielectric properties are vital," warns DuPont’s Hsu. Indeed, the overall complexity of connections will be increased, with more seals required.
"The main difference in the wiring system will be the need for more sealed connections, probably of a different design than 14-volt connections," says Wright. However, the higher voltages and lower currents associated with 42-volt systems will allow engineers to reduce wiring thicknesses by approximately two-thirds. "There is the potential to reduce the size of wires that are currently larger than 0.35 millimeter squared," explains Wright. "Circuits that are already 0.35 millimeter will likely not be reduced due to physical strength concerns."
According to Bowden, 42-volt motors will need to spend more time on winding machines. "They’ll require approximately three Arial as many turns as traditional devices," he points out. "But, since the wiring will be thinner, it will fill the same amount of space. Suppliers may have to invest in better winding equipment."
Suppliers are gearing up for this new manufacturing paradigm. For example, Xtreme Energy Inc. (St. Petersburg, FL) has developed a brushless motor with a patented coil that it expects will be used in many 42-volt applications. "We are automating the manufacturing process for our motor winding technology to address high volume requirements and price point issues in the automotive market," says Kirk Barker, president.
Traditional 14-volt systems rely on bulky wiring. Low-voltage electricity must flow at a high amperage to operate a vehicle’s accessories. That requires thick cables and harnesses. With 42-volt systems, however, wiring bundle size may be as much as 20 percent smaller.
"Harness and connector manufacturers will need to develop innovative products that meet automobile manufacturers’ needs in order to win contracts," says Jasmine Sachdeva, an analyst at Frost & Sullivan Inc. (San Antonio). "A top priority for automakers is to reduce the size and weight of wire harnesses and connectors.
"Growth in flat flexible cable and flexible printed circuit boards provide opportunities for growth. Suppliers that can design and develop new technologies that allow for size, weight and cost savings will definitely have a competitive advantage over other market participants."
Bowden says there’s a good possibility that new technology will be used, especially if it helps make wire harnesses smaller and more flexible. "Etched tri-metal and flat wire technology is not conducive to 14-volt systems," he points out. "But, they may be attractive to 42-volt systems."
Assembly ChallengesHigh-voltage components, such as alternators, connectors, relays, starters and switches, will be assembled similar to traditional 14-volt parts. "Assembly methods will be basically the same," predicts Wright. In fact, he says the transition to 42-volt systems will have a minor impact on assembly equipment.
"For the most part, current assembly equipment should be acceptable," explains Wright. "Only minor modifications may be necessary." He believes current test and inspection equipment will be acceptable, although slight modifications may be necessary, because additional quality checks may be required.
Many suppliers are taking a wait and see attitude. "We won’t learn more about the 42-volt systems until they are deployed and in production by the automobile manufacturers," says Peter Doyon, vice president of product management at Schleuniger Inc. (Manchester, NH).
Some equipment manufacturers are concerned about standards changing as development efforts continue. According to SAE’s Norman Traub, when systems reach the production phase, standardization will be needed to encourage suppliers to produce higher volumes.
No matter what transpires or when it happens, Richard Bodine anticipates there will be a tremendous opportunity to use new assembly equipment. "Suppliers will be asked to make new, lighter, less expensive and more efficient devices," Bodine predicts. "If you have a chance to make a product, such as a motor, half as big because of the inherent advantages of 42-volt technology, why not use new assembly lines and new equipment to produce it?"
Bodine believes the new generation of electrical components will undoubtedly be smaller than what we’re used to seeing today. "All you have to do is take a look under the hood of a 1948 Packard," he explains. "The 6-volt starter motor is much bigger than what you’ll find in one of today’s 14-volt vehicles."
Final vehicle assembly will also be affected by 42-volt technology. "If electrical troubleshooting is required at the assembly plant, it will need to be done with the battery disconnected," warns Wright. "Additionally, it will probably be desirable to connect the battery after all electrical connections have been made, which is not a requirement today.
"At the vehicle assembly level, some additional components will be required," adds Wright. "These include two batteries, a DC/DC converter and potentially other devices related to circuit protection and battery disconnection. Given the current packaging challenges faced by the auto industry, these additional components will exacerbate the situation further, which may challenge the assembly process somewhat."
Eventually, 42-volt systems may spur other changes in the way in which vehicles are assembled. For instance, the incandescent bulbs currently used in lighting systems may eventually be replaced with light-emitting diodes that can withstand higher voltages and are much more energy efficient.
And steer-by-wire systems may lead to the eventual elimination of traditional steering wheels in favor of joysticks. When that happens, it will probably inspire Jimmy Buffet to write another song.