Automotive 12V Standard


#1

Around the time of the R12 phase-out my instructor said the next big expensive change we will see is a change from 12V to 42V this higher voltage would allow for less wiring and more reliable data busing.Are there plans to go off the 12V standard? Not everything is going to be full electric.


#2

"A few years ago, there was lots of serious talk of cars transitioning to 42V supplies, either in addition to, or to replace, the venerable 12V system they have used for decades… "

Read the full article from 2/2006 here:

http://www.planetanalog.com/columns/mixed_signals/showArticle.jhtml?articleID=178601458


#3

The next big expense will be the phase out of R-134a. While it’s not as damaging to the ozone as R12, it’s still pretty bad stuff.
Engineers are having a difficult time finding a replacement that meets all the EPA requirements for toxicity, ozone depletion, etc. Oh yeah, it can’t be flamable either if the A/C evaporator is placed inside the passenger compartment (like it is on all cars right now).
Some companies are looking at using CO2. The downside is that the system will operate at much higher pressures and has the potential to become less reliable (several thousand psi on the high pressure side of the circuit). It’s also not as efficient as many other systems.
Others are looking to use a more flamable refridgerant that will require them to put the evaporator in the engine bay and use a separate heat transfer system to pull the cold air into the passenger compartment.
Either one of these systems is far more expensive that what is being used now.

As far as 42V electrics, it’s basically dead in the water right now.


#4

I remember reading about this several years ago, but haven’t heard a thing about it recently.


#5

I first read about going to a 48 volt system about 25 or so years ago in a trade publication and the way it was presented at the time meant that we should already have 48 volt electrics in all or most cars.

If I remember the spiel correctly, it basically stated that by the late 90s cars would be equipped with so many computers, sensors, etc. that the wiring would have to be downsized to cram it all into the car. Smaller wiring of course means the voltage has to be stepped up to enable the wire to carry the required current amount. Nothing to this point though.

The problem with higher voltages is that a huge new set of problems will develop (fire hazards more than likely) and the price to repair anything electric would absolutely soar through the roof. Can one imagine the cost of 42/48 volt batteries, alternators, starters, etc.?


#6

I imagine that the cost of 48 volt starters and alternators would be exactly the same as the 12 volt ones, maybe even less expensive. With higher voltage comes lower current.

Six volts used to be the standard as late as the mid 50’s. Did the price of starters and generators go through the roof when that voltage was doubled to 12?


#7

I agree with BLE that moving up to 42 or 48 volts should not affect the price of accessories. A motor or pump that uses 5 watts, for example, would essentially be the same as its 12v counterpart. It would use finer gauge wiring.


#8

Went to the link: It appears the need to go to 42V was overstated and limited reasearch re-tooling dollars have been diverted to full electric,hybrid,alternative fuel vehicles.Now on to the refridgerant change. Thanks


#9

The article quoted does not address the fundamental difficulty with a 42 volt system which is arc interuption or stated simply: switching. A higher voltage dc resistive load is somewhat more difficult to switch than a similar voltage ac load but an inductive dc load is very difficult to interrupt or switch off. It can be done but switches can not be simple contact switches but instead must be equipped with arc suppression or extinguishing means.