What happened to 24-volt electrical systems?

[Exit32]

A few years ago, there was talk about going from 12-volt to 24-volt automotive electrical systems. The reason given was that accessories such as power windows, air conditioning, audio systems, electric radiator fans, etc. were in danger of overloading the existing 12-volt systems.

I haven't seen any recent discussion of major automotive electrical system upgrades. Did the manufacturers decide that 12-volt systems are adequate? Maybe alternators are better today than they were 10 years ago? Or maybe I've just missed any new information about this.

 

[user52165]

Actually it was 42 volts - at least in parts.

Also designed to cut down on the increase in wiring size, gauge, weight, cost, etc.

I forgot for which limited production luxury car, but the total wiring length was....................... 8 MILES!

 

[spackard]

Well, guess what the new total wiring length would be?
8 miles.

Out on a limb here: the great recession postponed any transition plans.

 

[fields]

Think you will see some of these systems soon in the more expense cars. They will be used to power air conditioning, turbos(prevent lag), and starters. Think 12-14 volt systems will still power low draw equipment.

 

[MCompact]

The upcoming Mercedes proper(inline) six will use a 48 volt electrical system

 

[Kuato]

LEDs and other more efficient electronics may have played a part as well.

 

[BrocLuno]

24V is common in marine and aviation. Just not automotive ...

 

[Tomioka]

I've kept hearing chatter about 36, 48v systems that were supposed to replace engine driven accessories in regular gas/diesel engines such as the water pump, P/S and AC leading towards a beltless engine. Hybrids have already accomplished this.

 

[Silk]

Originally Posted By: BrocLuno
24V is common in marine and aviation. Just not automotive ...


Trucks (real trucks, not pickups) have been 24v for over 70 years.

 

[user52165]

Originally Posted By: Silk
Originally Posted By: BrocLuno
24V is common in marine and aviation. Just not automotive ...


Trucks (real trucks, not pickups) have been 24v for over 70 years.


Generally that is for the starting system. The cab and other systems are usually 12V. YMMV.

 

[Silk]

All large trucks I've worked on are 24v throughout, the whole system is 24v. I keep a full set of bulbs in stock...12 and 24v.

 

[supton]

I keep seeing bits about it in the trade mags but it just hasn't happened. I suspect there is too much stuff that runs at 12V (and these days too much that runs at far less).

Some of it may be hype. Headlights can't get brighter; and with LED's taking over, they don't need more power. Window defrosters and window motors have been getting by on 12V, so why change? Then there is the hybrid move. Which prefers even higher voltage. But doesn't need to be any place other than between battery and motor(s).

I read a comment from a GM engineer who said their internal specifications would not allow wiring below 22g (something like that). Otherwise the wires were more likely to break while being pulled (either making the harness or during repairs, dunno). If internal quality specifications won't allow a thinner wire than a certain point, then there is no gain. And think about: lots of wires in the car are not being used at high current, but rather at milliamps. Button for the window, wire for the overhead light, etc. And of course, doing a repair on a thin wire can be an exercise in frustration (think about the random initial failure in a crimp on a new car).

There's also stuff that doesn't need to be or won't run at 42V. Is there a need to string along lots of LED's for the overhead light? Probably not. Only need 4 or 5 volts for a single white LED; and to buck voltage down from 42V to what is needed without wasting power and/or making heat means money on a convertor. Many sensors are content at 5V and interface to an ECU that runs at a similar low voltage.

 

[chrisri]

Originally Posted By: Silk
All large trucks I've worked on are 24v throughout, the whole system is 24v. I keep a full set of bulbs in stock...12 and 24v.


That is Euro system, has been at least from 1970- probably even earlier.