42-Volt Switch To Help And Hinder Aftermarket

By Amy Gilroy On Nov 13 2000 - 8:00am

The switch from a 12-volt to a 42-volt power system in the car is expected to begin in two years, but aftermarket suppliers are still uncertain about the impact it will have on mobile electronics, and how the transition will occur.

Autosound companies are concerned that the shift to 42 volts will make head units more expensive because head unit parts must be regulated down to 5 or 8 volts. On the other hand, amplifiers may benefit from the extra power, which could result in better performance, smaller size and possibly lower costs, especially in built-in amplifiers under 100-150 watts maximum.

The move to 42 volts was prompted by demand in the car for more convenience features, such as electric seat warmers for all four passengers and improved electric windshield de-icing. Just as important is the need to convert mechanical car accessories to electrical-based systems, such as power steering and braking systems, for fuel conservation and lower emissions.

Forty two volts was selected because it is three times the present battery power used in vehicles. A 42-volt car would use a 36-volt battery vs. the 14-volt car, which uses a 12-volt battery.

At present, a committee called the Society of Automotive Engineers Strategic Alliance is hashing out standards for the 42-volt switchover, which Dennis Wiese, General Motors program executive for 42 volts, called "almost certain to happen." (See Aug. 7 issue, p. 29.)

"The two main reasons for the changeover are simple," explained Wiese, "smaller wires and smaller semiconductors. As we start to use more and more electricity in the car there's a point where the alternator can't produce enough power and the wires are so big you can't route them through the car.

"Consumers want more and more features like electric heated windshields and heated seats, and in the quest for fuel economy there are devices like power steering that we want to convert from mechanical to electric-and that will drive the need for more electricity."

The shift to 42 volts could result in improving fuel economy and reducing exhaust emissions by approximately 15 percent, noted Upton Bowden, Visteon higher voltage technical manager.

But the path for the changeover from 12 to 42 volts on the part of the automotive industry is still in question, creating headaches for autosound suppliers. Car suppliers will likely switch over in different model years, anywhere from two to five years in the future. Some may provide dual outlets for both 12- and 42-volt wiring harnesses or they may offer only 42 volts.

Said Alpine VP marketing Stephen Witt, "There will be some vehicles with 12 volts, while some more aggressive car companies introduce 42 volts, which will make it very complicated for autosound manufacturers."

General Motors said it is considering a gradual switch-over, offering both 12- and 42-volt plugs so that the audio wiring harness would still be 12 volts for several years. Visteon said several car manufacturers are likely to do the same starting in 2004.

"Within two years there will be vehicles with both 12 and 42 volts," Weise said, "and you'll see vehicles with just 42 volts starting in 2007. That doesn't mean you won't have 12 volts, there will be adapter products and DC/DC converters built into the vehicle. We'll still have to be able to jump start 42-volt vehicles from a 12-volt vehicle.

"I don't think autosound equipment will be more costly. It doesn't make a great deal of difference to convert from 14 to 5 volts or 42 volts to 5 volts."

But aftermarket suppliers disagree. A few car companies, including BMW, are reportedly considering converting to a full 42-volt system as early as two years from now. And aftermarket suppliers are concerned they may be forced to produce head units that can operate on both 12 and 42 volts.

Clarion director of product planning Jack DeBiasio said, "It will definitely add cost to a head unit, but the cost premium is unknown. It's true it is easy to step down from 42 volts, but as you get higher voltage the components cost more to handle that higher voltage. We use a 16-volt capacitor, but now we would have to use a 50-volt capacitor, so it's more expensive."

Some aftermarket suppliers are also concerned about the need for dual-voltage radios to accommodate the various plans of all the car companies.

"Dual-voltage products would be more expensive," said DeBiasio, "but depending on the volume, it may be a better way to go. And from the dealer standpoint, he may not want to stock both units. So there's a lot of research that needs to be done on the cost tradeoffs.

"We also need to know how fast 42 volts will be used by the car manufacturers. There are no firm timetables. It could happen as early as a few years from now, but there's a lot of work to be done."

The biggest impact of the 42-volt changeover on the aftermarket is expected to be on amplifiers and powered subwoofers. Onboard amplifiers will be able to "run barefoot" or forgo switching power supplies at up to 100 or so maximum watts.

The lack of a switching power supply will also reduce the amplifier size (particularly important for in-board amps), as well as reducing cost. In addition, it may increase the popularity of Class D and digital type amplifiers, which have been plagued, until now, in part by the noise from the power supply.

Rockford Fosgate VP engineering Jim Strickland said, "What I think is most likely to change is there will be amps that can be more powerful per dollar because you won't have to put in power supplies to step up from 12 volts to 50 volts. So one could take and make almost 10 times as much power off of 42 volts as you could off 12 volts directly. Amps will be smaller and higher power.

"The other thing is not going through a first supply can make the amp more efficient. At 100 amps of current, you start to get losses in some high-powered amps and you lose tiny portions of the 12 volts. So a system on higher voltage would have much less of that problem."

Of course, higher-powered amplifiers above 200 watts maximum will continue to require switching power supplies, and not everyone is convinced there will be a significant impact on the amplifier due to the 42-volt switch.

MB Quart president Keith Lehmann said, "Theoretically, you can increase the output and it will improve the ability of an amp to make more power. But engineers are just now starting to get their hands on this, so it's still all theory."