It's been just about 10 years since the auto industry was abuzz with the impending transition of automotive electrical systems from 12 volts to 42 volts. Didn't happen. Isn't gonna. Stop holding your breath.
In the first place, why on earth would the car industry make such a global change, obsoleting trillions of dollars in 12-volt infrastructure and aftermarket accessories? Simple: Twelve wasn't cutting it anymore. Wiring harnesses were getting heavier and bulkier to run all the power accessories on board, such as heated seats and power windows. With 42 volts in the system, vehicles could use thinner-gauge wires and smaller motors because the higher voltage would mean reduced amperage--and amperage (or current) is what dictates the wire size, not the voltage.
The bundle of wires that go from the car into the driver's door is a good example: Some luxury cars had more than 60 wires in a bundle as thick as your wrist, making the bundle unwieldy to install and prone to damage. Switching to 42 volts, however, could shrink the bulk of the bundle by half.
So, much was about to change, with air conditioning and power steering going from belt-driven compressors and hydraulic pumps mounted on the engine to electrically driven units mounted in a more convenient place--anywhere out of the crowded, overheated engine compartment. A second bonus would be the reduction of parasitic losses from the power-steering hydraulic pump, which draws power full-time, but is only necessary when turning the steering wheel. Ditto for the air-conditioning compressor, which has a relatively short-duty cycle on moderate days or after a car initially cools off.
Idle shutoff was another Next Big Thing: It would replace the engine flywheel with a giant motor/generator running off 42 volts, while substantial fuel economy gains would come from shutting off the engine at traffic lights. When you took your foot off the brake at the green light, the higher-voltage, high-capacity starter motor would spin the engine up to running speed before you could get to the gas pedal. These days, hybrids have high-voltage starter/generators integrated into their systems to achieve this, while a couple of German manufacturers are about to implement idle shutoff into their conventional 12-volt systems with substantial upgrades to the starter motor.
Current electrical systems aren't even 12 volts; technically, they're 14 and change. And lead-acid automotive batteries are actually 12.6 volts, not 12, with the system running at 13.5 to 14.5 volts during normal operation with the alternator cranking out enough juice to run the car and accessories and to recharge the battery. The upgrade to 42 volts, then, would have actually tripled the voltage. Someone decided it would be best to refer to the new wave as 42-volt systems rather than 36-volt ones. (Just to confuse the issue, aircraft have had 28-volt electrical systems since practically the dawn of aviation. Or is that 24 volts? Whatever).
So what went wrong here? The automotive industry found that switching off 42 volts wasn't that easy. Huh? A mechanical switch for, say, the window motor, has two metal s (well, a bunch, actually). When you press a switch, the two move into with each other and current flows to the motor. When you let go, they snap apart, interrupting the flow of electricity. But this doesn't happen instantaneously--the surface area of the metal s that touch doesn't go from something like 10 square millimeters to nothing in zero time. As the s move apart, the current density goes up in inverse proportion to the remaining area. And at the last instant of , the current density is high enough to melt and then vaporize the surface of the metal as a short electrical arc bridges the widening gap. Eventually, the s wear to the point that they don't work anymore. In a 12-volt system, this phenomenon was controlled by careful design and attention to the metallurgy of the s themselves. Forty-two volts draws a much longer, hotter arc, and vaporizes more metal.
Contact erosion on 42-volt systems was unacceptable, unless automakers upgraded the switches with more expensive metals and stuff such as spring-loaded s that jumped apart faster to reduce the arcing. Would you accept a car that had to have the switches for the power windows replaced every 10,000 miles?
Now why exactly isn't this an issue with 120- or 220-volt household switches, running 10 to 20 times the voltage in your car? Because household power is AC, not DC. The AC stands for alternating current. The voltage in AC wiring takes a huge swing--from 120 volts positive to zero and on down to 120 volts negative and back--60 times per second in a neat sinusoidal wave. And the arc just fizzles out as the voltage crosses zero 120 times per second, making for a clean break. DC, or Direct Current, constantly remains at its rated voltage.
High-voltage system were slated to appear as secondary systems on cars and trucks, with the normal 12-volt wiring in place until the industry gradually changed over. That was necessitated partly by the need to transition the industry to high-voltage components and practices. Just imagine the changes needed for the aftermarket accessories and electronics industries to redesign all of their components to match, and you can start to explain the death of the superelectric car. Oh, and you can bet it would have been more expensive to have two separate electrical systems on every vehicle. Not to mention it would have made electrical troubleshooting even more of a nightmare.
Innovations such as wire multiple have reduced the size and mass of low-voltage harnesses, and electrical power steering, after 10 years of development, now operates well on 12 volts. Meanwhile, manufacturers found other ways to improve fuel economy--idle shutoff being only one of them--without overturning the entire industry. And now we have hybrids with 250-volt-plus batteries and inverters to run the starter motor. Consequently, 42 volts has just dried up and blown away. Which is fine, because I really didn't want to replace a lot of tools, test equipment and battery chargers to keep up anyway.