Turning on the Juice

A raging thunderstorm knocks out the electrical power in your home, and you've got 20 pounds of milk, eggs and meat spoiling in the refrigerator. So what do you do?

If your vehicle has a 110V ac power connection, you take the food outside, plug a portable fridge into the car, and save the day. More and more, such scenarios are becoming realities, especially as high-voltage hybrids reach the market. With electrical architectures supporting 300, 400, 500 and even 600 volts, this new breed of hybrids will offer far more accessory power than today's conventional vehicles, and could open the door to a multitude of new features. Some vehicles could have so much on-board power that they'll allow truckers to run air conditioners while they snooze, without idling their engines. They'll serve as enablers for electrically-assisted steering in SUVs. They'll allow contractors to run power tools and outdoorsmen to plug in heaters. They'll permit automakers to add such features as pre-heated catalysts, thus lowering a vehicle's emissions every time it starts up. And they could even serve as the foundation for future technologies, such as steer- and brake-by-wire.

"There are a lot of possibilities when you have a higher voltage electrical architecture in your vehicle," notes A. J. Lasley, chief engineer for advanced powertrain and power electronics at Delphi Corp. "That's one of the advantages that a hybrid powertrain brings to the market."

Indeed, Ford's Escape Hybrid already sports a 330V architecture, which places it far ahead of the 42V architectures proposed a few years ago, and leaps and bounds ahead of today's conventional 12V vehicles. Similarly, Toyota's Prius works off a 500V architecture, while an upcoming Lexus hybrid SUV promises a 650V system. These higher-voltage architectures are currying favor among automotive engineers for a simple reason: power. The Escape's 330V system allowed Ford engineers to endow their hybrid with 2.5 kW of accessory power, about 60 percent more than is available on today's conventional vehicles. And that may just be a taste of what's to come. Some engineers are talking eight, 10 and even 20 kW within a few years.

"In future vehicles, the power that's going to be available for accessories will grow to anywhere from eight to 10 kilowatts," says Tom Watson, hybrid propulsion systems manager for Ford Motor Co. "Since we're supposed to put together designs that will last a number of years, we want to have enough power to satisfy the consumer features that no one has thought of yet."

Beyond 42V

Though not all automotive engineers agree that the trend will yield a raft of new consumer features, most acknowledge that the extra power will provide much-needed headroom. With today's conventional vehicles offering a scant 1.5 kW of power, engineers complain they are bumping up against the limits when trying to add such features as heated seats, electrically-assisted steering systems, electric air conditioning and pre-heated catalysts.

That's why many automotive groups supported the idea of 42V architectures back in 1999. With the prospect of power-hungry, drive-by-wire technologies looming on the horizon back then, concern over power budgets grew to the point where many engineers believed that 42V architectures were imminent. Ultimately, however, most of those efforts fizzled.

Automotive engineers say the primary reason for the failure of 42V is its cost. Instead of making the costly effort to move all conventional vehicles to 42V, engineers instead employed interim measures — smarter controllers and more efficient alternators — as a less costly way of solving the dilemma.

"It's a natural engineering phenomenon," Watson contends. "There's nothing like the threat of some new technology to stimulate innovation in the old technology."

For hybrids, however, it's a different story. Hybrid work is essentially driven by growing concerns over fuel economy and emissions. Hence, as automakers engineer their new hybrids from scratch, they're focusing on the development of vehicles that will make full use of electric power. In many cases, the new breed of hybrids employs big drive motors and sophisticated regenerative braking systems, as well as complex controllers, power boards, inverters and cooling systems.

"The trend we're seeing is that car makers are leaning toward very large electric machines," notes Mike Gauthier, director of corporate technology in North America for Siemens VDO Automotive.

As a result, makers of hybrid systems are rolling out vehicles with high-voltage architectures. Ford's Escape and its newer Mariner already incorporate 330V architectures. Moreover, several auto companies are working on vehicles with electrical architectures in the 500 to 650V range. At the Frankfurt Auto Show in September, Siemens VDO unveiled a modular concept for hybrid drives "in anticipation of full hybrids with electrical outputs of 75 kW" by 2008.

	Its 330V electrical architecture provides the Ford Escape hybrid with about 2.5 kW of accessory power, about 60 percent more than today's conventional 12V vehicles.

Room For New Features

With the availability of such systems, automakers and vendors say they can now begin to think about power-hungry features that couldn't be incorporated previously. Prime among those is electrically-assisted power steering. Many automakers want to put electric steering on today's vehicles, but have found the task to be next to impossible in bigger vehicles, particularly SUVs, which are already teetering on the brink of exceeding their 1.5 kW power budgets.

"One of the limitations of electric power steering today is you simply can't put it on a larger vehicle or truck," says Robert Schumacher, director of advanced product development and business strategy at Delphi Corp. "In most cases, it would cause the electrical system to be overtaxed at peak times."

With future power budgets in excess of 10 kW, however, designers of hybrid vehicles needn't be concerned about the effect of electric steering on the power budget. In such cases, experts say, a high-voltage vehicle could simultaneously run the steering's electric motor, along with its brake lights, heated seats, rear defroster and window motors, without concern of an overload (see sidebar on next page). In contrast, today's advanced vehicle controllers are assigned the task of preventing the simultaneous operation of all those features.

Automotive engineers say a larger power budget could also enable other new features, including: pre-heated catalysts for reducing vehicle emissions shortly after ignition; on-board ac accessory power for plugging in tools and small appliances; variable valve actuation systems for improved engine performance; and electric air conditioning systems, which are now gaining popularity in automotive circles.

Higher-voltage architectures could also serve in over-the-road trucks, especially those with sleeping quarters. There, truckers could run heaters and air conditioners while they snooze, without idling the engine in order to supply power.

"Idling is very inefficient and creates a lot of pollution," Schumacher says. "If they have a hybrid with a lot of electrical power, they could operate the air conditioner or heater without all the emissions and without wasting gasoline."

Automotive engineers also say that high-voltage hybrids offer automakers an opportunity to boost reliability. By employing dc/dc converters to step their 330V systems down to 13.2V, Ford engineers say they improve the reliability of wiring and bulbs in lighting systems. "Your headlights and all the other bulbs in your vehicle see a very consistent voltage," Watson says. "You don't get the voltage spikes that tend to burn out bulbs and shorten their lives."

	TRW’s hydraulic Slip Control Boost — which works with a master cylinder to provide regenerative brake blending for hybrids — can operate in a 12V electrical architecture.

Moreover, many engineers see the higher-voltage electrical architecture as a foundation for an all-electric, belt-less engine, in which all the pumps for water, fuel, oil and steering, as well as the air conditioning compressor, are electric. The result would be the elimination of the traditional serpentine belts, as well as the parasitic losses associated with them.

"If you go to an all-electric system with a high-powered bus, you only use the power when you need it," Schumacher says. "You only use air conditioning power when you run the compressor. You only use steering power when you turn the wheels."

Weighing Alternatives

Automotive engineers stress, however, that the changeover to such infrastructures will be slow, and new features will initially be costly.

"Sure, the traction motors and higher voltages on the hybrid give you the power for peripheral functions," notes Bob Rivard, vice president of advanced technology and product marketing for Bosch Automotive. "But in the near term, you're not going to see a sky's-the-limit attitude about using (that power). You'll still have cost issues and pressures to optimize the existing systems."

Indeed, companies such as TRW Automotive are rolling out new features for conventional 12V architectures. The company's electric power hydraulic steering, slip control boost and active hydraulic braking, for example, are all aimed at 12V electrical architectures. All are designed with hybrid steering and regenerative braking systems in mind, thus suggesting that higher-voltage electrical architectures aren't necessary — at least for now.

"There's no reason why you can't have a 12V hybrid system," says Phil Cunningham, director of product planning for chassis at TRW Automotive - North America.

Moreover, some engineers point out that drive-by-wire systems — once considered the prime motivator for higher-voltage electrical architectures — don't have the industry support they once had.

"The higher voltages are available for steer-by-wire and brake-by-wire, but much of the industry is still discussing the cost-benefit trade-offs of that technology," notes Rivard of Bosch. "It's still not considered an optimal solution."

Still, the longer term view supported by Asian automakers and by Ford in the U.S. is one involving higher-voltage architectures and all-electric accessories, including pumps for fuel, water and oil, as well as air conditioning systems and steering systems. Using this scheme, engineers say, they'll get better reliability of bulbs, switches and wires, as well as more consistent current levels and less significant voltage drops. Moreover, many automakers are saying that the higher voltage systems make greater sense as they migrate toward hybridization of bigger cars and trucks, which call for larger drive motors.

"The lower-voltage hybrids will give you better efficiency than you'd get with a conventional vehicle, but they still don't provide the power you need to do full hybridization," says Watson of Ford. "For that, you've got to jump to something higher — at least 200V. Given the spectrum of voltages available in the electrical system, you get all the efficiency from the higher voltages, so why spend your time on the 'in-between' voltages?"

	Automakers hope that future electrical architectures will make it easier to incorporate pre-heated catalysts, which could dramatically reduce vehicle emissions. (Photo courtesy of Siemens VDO Automotive)

Reach Editor Chuck Murray at charles.murray@reedbusiness.com.