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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."
Can't wait to see what these new batteries are going to cost...
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This news is positively shocking!
If they had chosen -56/48 VDC systems, cars would be compatible with Telco systems.
I remember hearing that from a commercial back in the early 50's...
Never create an artificial ceiling.. as it will be exceeded.. always.
---- Booth was a patriot ----
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?
Does this mean if my new car has a 42v system and the car battery dies and leaves me stranded out in BFE, I have to wait for another 42v car to come by before I can get a jump? That would suck.
Sure it mentions Hybrids in there but we all know that it is the "luxury" cars driving these changes, larger power-supplies will require more power to charge, which in turn requires more fuel.
So excuse me if I don't "welcome" this so someone can have an even louder stereo while pumping even more chemicals into the atmosphere. So we can have 110v power supplies so... so what ? So a "busy exec" can have an even large mobile office ? So Ted and Rhona in the back can have a Playstation 2 each ?
I would say that goverments should be introducing regulations to reduce fuel emissions... but somehow in the country where this will be plonked into Canyenero style SUVs I doubt that the Oil President will concern himself with more fuel being used.
An Eye for an Eye will make the whole world blind - Gandhi
My neighborhood already rocks with jackasses with 3,000 watt sound systems in their cars. Just what we need, 12,000 watt sound systems at 3 in the morning.
of course, its because 42 is the answer to life, the universe, and everything!
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Now I can have 2 blue lights under my D-reg Ford Escort!
This will be really nice when I find myself needing a jump... now I'll need three or four 12v batteries daisy chained to do a jumpstart.
Not to mention the other downsides (easier to get shocked from 36+ volts, easier for the electrical system to fry itself in a flood situation, etc).
Is it just me, or is the automotive industry quickly moving to purely disposable/recycleable cars? When I look at a 2003 model car, I have a hard time picturing it still running and still together in 15 years. Really makes me wonder what a 2010 model car will be like.
Way cool. One of the arguments that the Big Three automakers have been offering for why they don't make ultra-efficient ICE SUVs is that they require more expensive high voltage electrical systems. That's also one reason (albit a minor one) why gas-electric hybrids are so expensive.
Car manufacturers have said that it is more expensive for them if their product line has to have two different types of electrical systems. If high voltage electrical systems are going to be standard equipment, though, that argument will disappear.
"Weapons should be hardy rather than decorative" - Miyamoto Musashi
I think that goes for OS's too
Oh great, now instead of merely shaking the earth as they drive by, cars with souped up stereo systems will be able to actually crack the pavement and lift small dogs several inches off the ground.
Humorless sig goes here.
Why exactly is the ability to attach more electrical crap to my car a good thing?
Oh, I know... It's so I can check my email, sip my Vente Latte, talk on the phone, keep my McMuffin warm all while driving.
Woo Hoo! I am so glad I will be able to do that. I hate it when I get distracted by driving.
Blocklevel: Practical Information Architecture
Saw this one coming when we bought a new car for my wife and it had a water cooled alternator!
Her car has more luxuries and gizmos than any of our previous cars: Navagation System, Universal Garage Door Opener, 11-speaker sound system w/ DSP, CD Changer, Rear hatch auto-closer (close hatch the last inch), 8 airbags, 16-way power seats, rear wiper arm, etc.. bla.. bla.. bla... and so on..
I talked to my mechanic about it and they already knew the 42-volt systems were coming. They said 42-volts was chosen to avoid amperages that would harm humans while providing enough capacity for all the stuff being piled onto the latest models.
It's a small miracle that the battery drain if the car isn't driven every day....
Check it out. Just $20 or so. Radioshack sells an adaptor but it's $99. Fucking rip-off artists. There are a couple of cars out today that have 110VAC outlets already.
One of the main advantages of the 42 volt system is that you can have electronic, rather then hydrolic brakes.
autopr0n is like, down and stuff.
but only as legacy from being military vehicles, 24 volt systems ae needed to crank some of the old and new massive diesil engines in the transport trucks ect. the hummer has the 24 volt system so that it can jump start(or in military terms slave start)a tractor trailor.
since some military trucks spend a lot of time sitting and not driving this happens more than you might wish to think
I used to have a cool sig, back when I cared
It seems cars will have dual systems for a while for legacy equipment."
My late Ford Pinto isn't legacy equipment, you insensitive clod!
You can always convert one voltage to another though, it just entails a little bit of loss. Besides, you'd still have to take down the voltage for sensitive equipment anyway. You wouldn't want to run a modern CPU on 42 volts, that's for sure :P
It's only an optimization point. If you have a lot of low-voltage devices, you want a low voltage PS, and the same for high-voltage.
autopr0n is like, down and stuff.
The only problem I see with this is that a 12V system cannot self sustain an arc while a 42V system easily can. If a 42V car gets in an accident, the higher voltage system may present a problem for emergency workers as they could receive a nasty electric shock while trying to open the car up to get the passengers out.
Except I don't drive it, I have a chauffer who does it for me, there are also lots of other people who share the same chauffer
An Eye for an Eye will make the whole world blind - Gandhi
It's just that more current will flow with 42 volts than 12 volts -- 3.5 times as much.
Also, to kill you, the current needs to flow through your heart (unless it's a LOT more voltage, pushing enough current to start cooking your flesh.) This means that you'd have to touch each terminal with a hand.
I remember the 68 volt batteries that they used for old flourescent lights. Even getting your fingers wet you could barely feel the voltage with them, and not at all having each hand touch a terminal. (Yes, I was a curious kid.)
In short, I don't see how 42 volts is going to kill you. Even 110 volts has a hard time doing it.
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.
NetInfo connection failed for server 127.0.0.1/local
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.
A 42-volt system will slash weight
...
... Okay, when the switch to 42V is made, then everything will supposedly be peachy. But that's not tomorrow : there are still cars around with 6V batteries, or negative hot, *today* while those standards are supposed to be long dead.
...
Where ? 12V lead/acid batteries have 6 elements, 42V batteries would have 21. That's 21 lead plates and associated acid cell. The only thing that would be lighter would wire harnesses, because the wires would be lower-gauge wiring since they wouldn't have to transport as much current. I can't see that being a real weight economy.
improve fuel economy
How ? do 42V alternators have a better efficiency than 12V ones ? And even if that was the case, wouldn't, say, driving the alternator with something else than a rubber belt improve efficiency much more dramatically ?
permit the replacement of many mechanical parts with electrical ones
How ? what are the mechanical parts that can't be replaced by 12V electrical equivalents that could be replaced by 42V ones ?
power all sorts of new gizmos like seat heaters, video, etc,
I can't wait to see cars with seat heaters or video units
and, of most concern to us, improve efficiency for all automotive electrical devices
I don't know about overall efficiency, but in all fairness, that's true : it's easier to step the voltage down than up. So yes, many devices would become lighter, cheaper and probably more efficient.
opening the door to higher audio amplifier power with far less complexity than the current crop of 12-volt, high-power amplifiers. Not only can will this translate to lower cost and more compact aftermarket power amps, even head units could cheaply integrate 100-plus RMS watts per channel power.
That's about the only application where I can see a 42V system be useful.
All I see in that "improvement" is trouble, exactly like when cars switched from 6V to 12V, and more money to aftermarket accessory makes. For many years, you'll have dual-voltage devices (complicated and defeating the purpose of having a higher voltage in the car) that will be more expensive and heavier, you'll have to buy another cell phone charger, power-supply, CB and whatnot, you'll have to use voltage converters, people without a clue will plug 12V devices in 42V cars, giving more money to garages,
In short, a half-load of technical shit, trouble for everybody and a lot of money for the automotive industry
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Well, Doc Brown had to go all the way to 2015 to get one...
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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.
The 2004 Chevy Malibu will launch this fall with a 42V electrical system and Delphi E-Steer electrical power steering. It's not full steer-by-wire; there's still a mechanical linkage. But that's for backup, through a flexible coupling. The real steering is done with a sensor on the steering column, a motor in the steering box, and a computer watching speed, steering angle, skid information, and such.
This will make converting cars to computer control much easier.
The new batteries shouldn't cost 3x as much either. Yes, it will have 3x as many cells, but the cells could be 1/3rd the size, which could give the battery the same capacity as one of today. Of course, they do expect higher electricity demands in the future, so batteries will probably get larger (and would have to do so even if we stayed with 12v) so the size and price of batteries will probably increase somewhat.
As far as providing 110V AC circuits, they can do this pretty easily and cheaply now, if they wish. 36V systems won't make this that much easier. (It will make it easier to provide higher capacity 110v circuits, however. A hair dryer draws 1500 watts, which is 10 amps at 110 V or 125 amps at 12 volts. 10 amps is a lot, and 125 amps is massive. Assuming a 100% efficient inverter (which isn't possible), a 36v system could would only need 42 amps to power that hair dryer. Still a lot, but the wires needed to power the inverter would be a lot smaller.
(Of course, 42 amps is still a lot, and so it's unlikely that many cars will have an inverter capable of producing 1500 watts of power. But 500 seems likely.)
And no, I wouldn't expect this to affect the 1000+ watt stereos out there much. A 36v system would make wiring up one of these stereos simpler, because you could use smaller wires, but other than that it would be the same. The stereo could have some smaller wires internally as well, so in theory it might be a bit smaller and cheaper, but I'd expect that effect to be minimal.
...and everyone would live forever, and no puppies would ever die and Al Gore was president and you had a meaningful relationship... Gosh - then things would just be so swell.
Cake or Death? Cake Please!
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.
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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.
Cake or Death? Cake Please!
Exactly. There seems to be a lot of fear about car batteries in general, because people have heard that "10mA of current through the heart can kill someone". They see "500A of cold-cranking power", and start to freak out. What they don't realize is Ohm's law.
.00008A, or .08mA. With a 42V battery, we get .28mA. Still WAAAY lower than what can even start to hurt a human. It doesn't matter how many AMPS the battery can put out, with that kind of resistance, that's THE amount of current it can push through.
V = I * R, or re-arranged for what I'm going to show, I = V / R.
I measured my body's resistance using a multimeter, and usually got between 150Kohm and 200Kohm (hand to hand, going through my heart). Plugging this in for a 12V car battery, we get I = 12V / 150Kohm =
I forgot to add that this could make them safer, too. Right now cars that have high voltage systems (e.g. hybrid or electric cars) usually have separate electrical systems; a high voltage one for the drive train, and a low voltage one for the rest of the car.
This is works, but it can cause fires if the high voltage system comes in contact with the low voltage one. Fires and high voltage systems in cars can be very nasty. This complicates the job of resuing people from an accident or repairing the car afterwards.
"Weapons should be hardy rather than decorative" - Miyamoto Musashi
I think that goes for OS's too
What is really needed more is a 12 volt battery that can provide current for longer periods of time. I would rather see a parallel system. 2 12 volt batteries with either 2 alternantors (one for car and all of it's internal acessories and one for the external plugin ones. Also, the second battery could also be charged off of regenerative brakes and or solar cells as well as a alternator.
:)
I don't see how changing voltage will make cleaner sound. The biggest problem with mobile electronics is lack of a good ground. The ground on a modern vehicle sucks. When I run a HF radio in the car, most of the losses are because of the ground system in the car. It's near impossible to fix that properly. The antenna systems in the car are almost always verticals and normaly you'd either burial radials or have a decent ground plane built. With a car, it's impossible to change the width of your ground plane because it's mobile. Mobile installations almost always require an antenna tuner because of this and this is just to make sure your SWR stays radio safe. You may have a radio capable of 100 Watts, but I have never seen one produce it. Plus the alternator produces alot of hash that needs to be blanked out or filtered out. RF chokes on the power cords and other things to get rid of this noise. When you run off of just batteries, that noise is not there anymore and you don't need those filters.
Gorkman
It is not that simple. As you apply higher voltage to your skin, its resistance will decrease very rapidly, and in the result the current flowing through your body will be much greater. And yes, 48V can kill you.
42V is below the threshold (50V) where the rules change concerning electrical safety. It is still considered a low voltage circuit, with minimal risk of electrical shock and injury.
Mea navis aericumbens anguillis abundat
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.
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.
Are they going to change the cigarette-lighter plug and all obey the same standard? I can picture it now... "I plugged in my cell phone to charge, and then it started smoking....." I already need a hundred 12-volt adapters in my house for charging different things, don't need them in my car as well.
Peugeot 307. They didn't go full-multiplex, but a sizeable portion of the electric doodads is basically doing things the USB way: a pair of power supply rails, and a data bus through the whole car. Cheap terminal gizmos in front of each device to demultiplex. VoilÃ, less wiring.
So the wire can be 1/3 the diameter. (Ignoring the fact that the smaller wire won't dissipate heat as well)
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42 volt means thinner copper cables, it also means you can run an electric airco, instead of a mechanical mechanism the engine has to pull along all winter uselessly. This would actually make the car more eco-friendly. (Remember a car pollutes as much during production as during its entire lifetime on the road.)
10 ?"Hello World" life was simple then
I was always under the impression that clean amplification had to do with a clean, stable power source
Exactly. Thing is, more car speakers are 4-ohms, which means you can only get 9 watts peaks (6V^2/4ohms, cause the speaker will be virtually grounded in the middle of the supply) or 4.5W RMS with a single 12V supply. To get more power, you need a circuit to step up the voltage. With a 42V supply, you can get 110W peak, 55w RMS. A clean DC-DC voltage circuit is a significant cost of a car amplifier. You could decrease the effective resistance of the voice coil, but building an amplifier with sufficiently low output impedence is tough.
On the other hand, they could just go with the inelegant solution of designing an interface that makes it impossible to connect jumper cables.
We had to boost one of our cars the other day, and the only other vehicle handy was my father's Montana. The battery is in there in such a way that you cannot access the terminals directly, at least not without cutting away parts of the frame (or removing the battery, of course). To allow for boosts TO the van, they have a 'remote positive terminal' which you can easily access.
Only problem is, there is no 'remote negative terminal', essentially making it impossible to use his van to boost another car. Even the owner's manual insists you need a negative terminal to boost from, so it's not like there's some weird configuration of booster cables that I've never heard of.
Gotta love progress.
Endless arguments over trivial contradictions in books written by ignorant savages to explain thunder in the dark.
The luxury market does not drive any portion of the auto industry. It is the least profitable buisness segment. New tech appears in the luxury models only because that is the only economic way to proof it (beta testing). So the luxury lines provide a testbed for development, which justifies their existence. The auto industry does not ever develop tech that can not be applied across product lines.Doing so is not profitable
I have worked in the Automotive electronics industry, developing motor controlers, regulators, converters, etc. The 12V standard is the one single greatest impediment to the development of efficient electric/hybrid autos. A 12V motor will be at least 2 times the wieght of an equivilently powered 36V motor.
EMF (volts) != Power ( watts), idiot.
Higher voltage will result in smaller power supplies and more efficient systems. As a youngster, I use to maintain very high powered 12 volt electric equipment ( Power[P] = EMF[V] * Current[I] ( amps)
P = I^2 * Resitance[R] ( ohms)
R = Constant * Length / CrossSectionalArea[A]
(BTW this P is waste == inefficiency)
This means that for a given efficiensy, the wieght of the wiring is proportional to the square of the current. I.e. Twice the current needs 4 times the copper.
W-e-l-l if you've looked into the literature on turbocharging, you'd find that back pressure isn't usually a problem (unless it gets really high). The Wright R-3350 turbo compounds got about 20% more power by coupling the exhaust turbines through a fluid clutch. The idea is that there is a lot of wasted kinetic energy is the exhaust of a non-turbo'ed piston engine.
A Shadeless room is a brighter room.
A 42-volt system will slash weight
Where ? 12V lead/acid batteries have 6 elements, 42V batteries would have 21. That's 21 lead plates and associated acid cell.
Get with the times. Upping the voltage allows the same punch with less current, which allows the use of smaller, lighter, NiMH batteries. Of course NiMH could be built in larger sizes, but they're not -- and being able to use smaller, commodity sizes is a hell of a lot cheaper. In fact the Honda Insight and Toyota Prius use commodity NiMH 'D' flashlight cells chained together in a big battery pack. 35 of these in series gives a 42V battery with more oomph than a stone-age lead-acid wet cell, is longer lived, more reliable, hardly affected by temperature, and a fraction of the weight. In case you haven't noticed, car batteries are *heavy.* Engineers love to be able to reduce vehicle weight, but the real savings is in shipping cost!
the wires would be lower-gauge wiring since they wouldn't have to transport as much current. I can't see that being a real weight economy.
No, but it sure is cheaper -- and more reliable. Higher voltage is less affected by bad grounds, corrosion, etc., which are the source of most vehicle electric problems.
improve fuel economy
How ? do 42V alternators have a better efficiency than 12V ones ? And even if that was the case, wouldn't, say, driving the alternator with something else than a rubber belt improve efficiency much more dramatically ?
Yes, higher voltage devices are more efficient. But besides that, the move is toward direct drive, combination, generator/starter/traction motors that live in the bellhousing like the one in the Honda hybrids. There's no belt, and no losses (or maintenance issues) due to that. There's one device, not two or three. It lives in a thermally stable, clean, dry environment. In ten years, more cars will have this hybrid-like architecture than not, whether or not they'll be true hybrids. It's simply a better way to build a car.
permit the replacement of many mechanical parts with electrical ones
How ? what are the mechanical parts that can't be replaced by 12V electrical equivalents that could be replaced by 42V ones ?
Electric air conditioning compressors, power steering and brake servos, etc., become viable with a higher voltage system. Higher voltage allows them to be smaller, lighter, cheaper, and efficient enough to surpass current technologies.
and, of most concern to us, improve efficiency for all automotive electrical devices
I don't know about overall efficiency, but in all fairness, that's true : it's easier to step the voltage down than up. So yes, many devices would become lighter, cheaper and probably more efficient.
Well if you don't know, then STFU. "I don't know what I'm talking about, but here I go anyway..."
And yes, many devices would become lighter, cheaper, and more efficient. A few watts here, a few watts there, it all adds up. A few dollars here, a few dollars there, that all adds up too -- except that automakers think in *fractions of pennies.*
opening the door to higher audio amplifier power with far less complexity than the current crop of 12-volt, high-power amplifiers. Not only can will this translate to lower cost and more compact aftermarket power amps, even head units could cheaply integrate 100-plus RMS watts per channel power.
That's about the only application where I can see a 42V system be useful.
I'm sure.
Remember the old saw: "it's the volts that jolts, but the mills that kills".
42 volts will make you jump - I work in the telecomms industry and know what 48 feels like - but you would have to take some care to get enough current from a 42 volt supply through your heart to kill you. It would be a terribly inefficient way to commit suicide. Electric chairs typically use about 2000 volts Amazing (and kinda sad) what you can find with Google!
...laura
Or "car... drive for me".
10 minutes later...
"A car has veered off route 66 and the driver's 2 children were killed. According to sources, the driver claims that she didn't realise the car didn't have an autopilot system, and by the time she got up from vacuuming the floor it was too late..."
== Jez ==
Do you miss Firefox? Try Pale Moon.
A higher voltage electrial system probably wont have much effect on the maximum power output of car sound systems although it may allow for more compact amplifier design. The reason for this is that car amplifiers use a DC-DC converter to generate the necessary voltages. A typical amplifier capable of delivering 100W RMS into a 4 ohm load requires about 80 volts (+40v and -40v). Even with a 42v electrical system a DC-DC converter would still be required.
the speed of sound used to be thought of as a natural ceiling.
when religion is no longer the opiate of the masses, governments will resort to real opiates.
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.
42V is enough to pass through dirty water, so I anticipate all kinds of problems when things get wet, unless everything is carefully designed to tolerate some electrical leakage. On the contrary, a 12V motor will actually run underwater with no sealing!
When I am king, you will be first against the wall.
For electronics that a consumer can contact, the voltage still needs to be limited. With lots of grounded metal nearby, doing auto wireing is kinda like wireing your house circuit breaker panel while standing in a puddle in bare feet. It's not a great idea at high voltage.
.25 hoursepower and in the 12 volt example it's about 5.3 horsepower gone to heat.
This means that for a given efficiensy, the wieght of the wiring is proportional to the square of the current. I.e. Twice the current needs 4 times the copper.
Anybody want to take a stab at figuring wire sizes for a 1 volt drop in two examples below? If you do, figure a wireing length from battery to comverter (AC Variable frequency, variable voltage) to engine alternator/startermotor to drive motor, regenerative braking loop of about 15 feet. (7 feet each conductor + & -)
Anyway, the Toyota Prius uses a 300 volt battery for the electric drivetrain end of things. That keeps the wire sizes reasonable. For compatibility, it uses a converter to keep up a 12 volt battery (motorbike sized) for the lights, computer, instermentation, etc. The battery is small because it is not used to crank the engine. The 300 volt does it. If they dropped the voltage by 10, the current required to do the same job would go up by a factor of 10. Therefore a motor instead of running 200A at 300 volts would run 2,000A at 30 volts, or (ready for the 12 volt system) 4,000 Amps at 15 volts.
Here is where the big losses in low voltage systems come from. Drop 1 volt in the 15 volt system due to 4000 amps in a very large wire and your loss is 4,000 Watts. Can you say hot wires! Drop 1 volt on the 300 volt line at 200A on a much smaller wire and the loss is only 200 Watts. You can use a much smaller wire to get a better job done.
At 746 watts per horsepower, the loss in the 300 volt example is about
Driving a Toyota Prius is an experiance. It has the get up and go of a V6 even though it's a 1 Liter 4 cylinder engine. It gets it's merge to the freeway with a combination of gas and battery power. The engine auto shuts off for stoplights (restarts as you take off again) Other than the silence at a stop sign or light, you would never know the engine shut off. Because of this, it gets better milage in stop and go city traffic than freeway driving with it's high wind resistance. These would be fantastic for a fleet of taxies.
The truth shall set you free!
Right now nearly every add on in a car (radio, cell charger, that sort of thing) uses a version of the 7805 or 7812 regulator. These devices can cope with voltages up to 40V and thats considered reasonable based on surges on a 12 v system. With a 42V system, that already exceeds the input voltage of most low cost voltage regualtors and when you figure in for surges at 3x, its outside of all the low cost DC regulators. The resut is a part that is now a single 5 volt regulator may need a swtiching power supply until someone comes up with a 7812 style device that can cope with the much higher voltages.
check out the MIT/Industry consortium. They have links to news and research as well as all the major industrial players.
One advantage I haven't seen in any of the previous posts is that 42V provides enough power for components to be moved off of the serpentine belt and away from engine. The change from mechanically powered to electrically powered has the potential to drastically alter the design of automobiles by distributing components around the vehicle instead of everything being lumped together under the hood.