42V electrical systems in cars

Most people would agree that there have been radical changes in the design of automobiles in the last 15 years or so. Not only do computer chips now control the entire operation of car engines these days, they also control the automatic transmission, brakes (ABS), the air-bags, cruise control, traction control, air-conditioning (climate control) and even suspension.

But as radical as those changes are, they are just for openers. We’re going to see a lot more changes in the next few years as designers work out how to make cars perform a lot better while using less fuel and providing more safety. A fundamental part of this next raft of changes will be the electrical system itself.

The old faithful 12V system will be superseded by 42V systems, based on a 36V battery but acknowledging the fact that the actual DC voltage will be maintained at around 42V. This is equivalent to 14V from an existing 12V battery system. The proposed 42V system is described this month in an article starting on page 4.

The main reason for going to the higher voltage is that the electrical load in cars is getting higher all the time. Increasing the voltage by a factor of three reduces the current by the same factor and this greatly reduces voltage losses as well as enabling the wiring harness to be reduced in weight.

However, some of the changes envisaged for cars involve such things as electric power steering, electric blower super-charging and even solenoid-operated valve trains. These really do involve quite high peak powers but they are better done electrically rather than driven by the engine. They would not be really feasible at 12V but they become a whole lot easier at 42V.

The most exciting concept has to be computer-controlled valve trains. These could bring about quite startling increases to engine power and responsiveness, as well as completely eliminating all the drawbacks of existing camshaft and valve lifter systems. In fact, this would make existing variable valve timing schemes such as Honda’s VTEC and Toyota’s VVT seem crude in the extreme. Instead of bringing a more aggressive cam profile above a certain engine speed like these mechanical systems, a computer-controlled valve train could apply infinitely variable valve timing, from cylinder to cylinder if necessary.

So if you suddenly wanted heaps of power, not only would the fuel charge increase but the inlet valves could be wide open to accept that charge, instantaneously. Possibly the system might end up being so effective that it would make super-charging or turbo-charging obsolete. You could have car engines that were completely docile and very economical most of the time, only to change to fire-breathing monsters in the blink of an eye.

Now maybe we could have roads where we could use all this extra performance. Energy crisis? What energy crisis?