42-Volt Autos

brianlmoon writes "Car Audio Electronics Magazine has a story about the auto industry switching to 36/42-Volt systems starting in 2004 and being completely switched by 2020. The demand for luxuries in cars has grown to where 12/14-Volts is just simply not enough. The automotive sound enthusiasts are going to benefit greatly as amplification will be much easier and cleaner with 3 times the voltage availble. Mobile computing will also benefit: "One of the real benefits of jumping to 42-volt systems, especially for hybrid vehicles, is the ability of the vehicle to offer regular 110-volt electrical outlets". It seems cars will have dual systems for a while for legacy equipment."

More accidents?

[roryh]

Most car drivers I see don't pay enough attention on the road as it is, and that's without the ability to plug in household applicances. Multi-car pileups because someone was checking their email or pr0n?

Some basic EE facts

[Mononoke]

Higher voltage system allows lighter gauge wire to carry the same amount of current (weight savings).

Higher voltage systems are less affected by corroded contacts and connections.

Higher voltage systems allow physically smaller fuses for the same power handling.

All of these allow cheaper cabling, connectors, fusing, etc.

Re:Ummmm...

[droleary]

Finally, how does 42V DC convert much easier to 120V AC? Don't you still have to use an inverter?

Yeah, that's exactly what I was thinking. You can already get a pretty beefy inverter for under $100 to run equipment from your car. I think this is just another case of the big auto manufacturers tacking another $1000 on to the price of a car instead of giving us really innovative vehicles like this [acpropulsion.com].

Re:This is obvious

[throwaway18]

I remember an article in an IEE magazine about this a couple of years ago.

A nominal 12V car battery produces about 13.8V when fully charged. When it is being charged the voltage across the terminals can be as high as
15.5volts. The voltage also varies with temperature and load.

Electrical systems must meet more stringent safety requirements if they use 50V or more. 42V was chosen to keep within the 50V limit during charging.

Some people are confused about the reasons for a higer voltage. The amount of power used is volts*amps. With three times the voltage things like head lights that will be made to use the same power will require a third of the current so the wires can be thinner.

Simplifying somewhat, with a 12v supply and an 4ohm speaker a transformerless amplifier can supply about 24watts rms (0.707*v^2/R),
which is more than enough for everyone except boy racers.
Move to 42V and an amp can supply 72 watts per channel (marketing will call it 150Watts music power) without an expensive and bulky lump of iron and copper.

Re:No more car tinkering...

[maxume]

The system runs at 36 Volts, The battery is the only thing that is 42 Volts. And there will actually be less current flowing with a 36 Volt system, 1/3 as much. Power = Amps x Volts; Increase Volts, and Amps go down, at a given power. The 68 Volt batteries you speak of probably didn't put out much power.

The issue with the new 36/42 Volt systems is that at a given power output, the electricity is more likely to choose you than it was at 12/14 Volts(yes, you have a 14 Volt battery in your car). So at 42 Volts, you get less current in the system, but the potential(the voltage...) is higher, and more likely to short. And the shorting is when you get hurt.

12 Volt systems generally don't have enought current available to actually short across you(except for a couple of spots), which I think is what the grandparent was talking about.

Re:2020!

[mtec]

Rap won't fade away - they'll kill each other off. It's all part of the new reality entertainment and part of the circuses we'll watch while Rome burns.

Re:That's bollocks

[Have Blue]

people without a clue will plug 12V devices in 42V cars, giving more money to garages

This problem is easily removed by making the plugs incompatible.

Re:dang, I need a jumpstart...

[XO]

I bet people said the exact same thing in the 50's and 60's when they went from 6v to 12v.

Well, similar things, anyway.

I've got a 1985 pickup that still runs like a champ, althogh it's got a lot of not-right parts mounted to it, and several pieces on the engine are outright broken. lol.

I've got a 1993 dodge daytona, that i just put a junkyard engine in, and it runs like a champ, too. actually, it runs better than it did new.

Re:Saw this one coming when..

[aaarrrgggh]

Actually, Ohm's law is V=IR.

A human has a given R-- add internal resistance of battery and wiring, and a given I will cause electrocution. Solve for V.

If you short a human across a battery, you will quickly electrocute them. Higher voltage batteries could possibly have higher internal impedance, but it isn't going to make it safer.

Still, a 42V shock isn't nearly as bad as one at 480V... you might still be able to pull away.

What higher voltage will really do is make the wiring smaller, and give them more options for higher-power equipment within the car. It's a compromise on safety.

Re:More accessories...new outlets

[ProfessionalCookie]

I just hope they come out with a better plug that the cigarette lighter plugs we're used to. I can't think of anytime I've ever seen anyone who actually uses those things to light cigaretters and apart from doing that they're absolutly horrid.

I think a plug that resembles the GC controller port would be much nicer. the plugs slide into place easily, you have to excert a just the right amount of force to remove them and they always connect perfectly.

Re:For those unfortunate times...

[PurpleFloyd]

Car batteries are still 12 volts. The alternator outputs 13.8 to charge the battery and run electrical systems while the car is running, but the battery provides 12 volts under normal circumstances. Don't believe me? Go get a multimeter and check your car. The 13.8V system is there to charge a 12V battery.

It's a long process, need to start now

[Nkwe]

The question is not do we need higher voltage systems in cars today; it is Will we need higher voltage systems in cars ten years from now? Cars are not like computers where a design change can be on retail shelves in a matter of months. Simple design changes in cars take several years before they show up in the dealer's lot.

If we, as a vehicular society, are going to want improvements in the stuff we can do with electricity in our cars over the next 10 years (very likely), we need to start working on changing the platform with which to do this now.

It appears that this is happening and this is a good thing.

Re:Oh great

[bigbadwlf]

Potentially less. They will be smaller.

Yeah, and CDs were supposed to cost less when they first hit the shelves because they were cheaper to produce.

Some suit will see this as a perfect opportunity to mark them up to line his pockets and the rest will surely follow suit.

Re:Where the power is

[thebigmacd]

No, you would have to go from 10AWG wire to 15AWG wire for example, which is still 68% the thickness of 10AWG. This is because cross-sectional area decreases at a rate proportional to diameter [radius] SQUARED.

Thats right, 2/3 the thickness not 1/3.

missing the boat

[illini_fan]

As far as the luxury market being the least profitable segment, that would depend upon perspective. First off, you must decide what is and what is not a luxury car. Let's assume we remove the near luxury market from the equation and peg the luxury market at 5 Series, E Class or equivalent and then on up from there. These cars definitely do not account for the majority of revenue or profit for the auto industry as a whole due to their relative limited production. However, these models tend to have a much higher margin. This is significant because the return on assets/investment for these products is superior to the more "bread and butter" cars. This is why a number of large auto companies such as Ford, GM, etc. have purchased foreign luxury marques. Higher margins normally translate to higher stock valuations. Just look at the successes that BMW, Toyota and others have had recently with their stock as a function of the operational performance of these companies due to increased margin. As far as the statement that luxury cars do not drive ANY portion of the auto industy, I do not think that is necessarily true. I fully agree with you that luxury cars are testbeds for new technology, but these advances often trickle down to "lower" vehicles over time as economies of scale and market preferences allow. One can only look to HID lamps, ABS, traction control, stability control, heated seats, etc. to see this process. It would be more correct to say that luxury cars drive the future of the auto industry. Your math is correct. At the end of the day, increasing voltage will give manufacturers more latitude for design as extremely high currents will not be necessary to achieve the same power output.

Re:Saw this one coming when..

[riedquat]

I think the idea is that with higher voltages you need lower currents to do the same job. The danger they're talking about here is not from electrocution but from overheating and sparking.

People have lost fingers due to getting their wedding rings between battery wires. At three times the voltage, that line could be fused at one third the current, so there's much less chance of damage. Starter motors, which aren't fused at all in my experience, could conceivably be fused at 42V.