This has been in the works for a while. I remember first reading about it maybe 5 years ago. The first link showed a drawing of the motor/generator built into the flywheel housing. I think this is one of the biggest motivations. They can build in a high powered electric motor and simplify the other electronics at the same time.
#33650 - 01/27/0405:36 AMRe: 42-volt car batteries
I read about this proposed change some years ago as well.
Some people installing their own audio systems have enough trouble with the wiring already. When a car has a dual 42 and 12V system on board, I can see all sorts of possibilities of copnnecting 12V equipment to a 42V line.
#33651 - 01/27/0406:00 AMRe: 42-volt car batteries
It's 14V and 42V OR 12V and 36V. The former is with the motor running, the latter is the nominal battery voltage. You can't charge a battery unless you have a higher voltage than the battery itself.
Big Jim is correct about the motor/generator, this is one of the improvements. Another advantage is that you can use electrical power steering on all types of cars. With the 14V system it only works well on small cars. You can make other things like AC electrical too.
#33652 - 01/27/0409:36 AMRe: 42-volt car batteries
The main reason driving the 42V system is the ability to use solenoids to directly actuate the intake and exhaust valves in the engine, eliminating the camshaft, lifters, pushrods, and rocker arms (and all the associated losses/friction). Direct computer control will also allow much more advanced VVT (variable valve timing) systems, reducing emissions. The current required to actuate valves at 12VDC is impractical, requiring huge wire and switching transistors.
Other accessories that will be electrically driven will be power steering pumps and A/C compressors. Running these at a constant speed pays dividends in efficiency and design simplification (cost), but power requirements make this impractical at 12 volts.
AFAIK, the new 42V cars will restrict the high voltage to systems that would have some real benefit. General lighting and accessories will remain at 12V, developed from the 42V supply by an electronic regulator.
[This message has been edited by NJwirenut (edited 01-27-2004).]