Another Car Battery question

Autos are going to use 34 volts in a couple of years. They are being designed now.

Bill K7NOM

Was supposed to 42 volts several years back - what happened?

"Ivan Vegvary" wrote in news:97Poj.33$f73.12@trndny08:

From what I've heard, they're going to skip 24V and go straight to 48V.

This will enable the use of 4 motorcycle-sized batteries that can be secreted in different areas of the vehicle for fuelled vehicles and 4 car- sized batteries for electric/hybrid cars.

The industry is working up standards for '42V' which will be a 36V battery with charge voltage circa 42 volts... just as '12V' has a 12V battery but charges at 14V or more.

Practically this will make the electronics compatible with telephone type gear (which has 48V battery backup) instead of the aviation/military gear (which uses 24V battery). Probably they think it's cheaper this way.

On Sat, 02 Feb 2008 00:50:13 GMT, with neither quill nor qualm, "Ivan Vegvary" quickly quoth:

I vaguely remember an article about that in Popular Science or Pop Mech years ago, but I don't recall why it didn't catch on. Price of components, probably.

We are in the process of switching to ? 72 ? volts IIRC. Yes high voltage. Low current. Less copper. Local power supplies for generating what ever voltage wanted. There are changes in the industry here and there and now a little more. I suspect the power for toys will ?maybe? be the same. You just have a local step-down switcher that can generate high current for boom box toys and nominal current for lights. Very clean for DVD and GPS and car CPU's.

Martin

Mart> Okay, so the switch from 6 volts to 12 volts (automobiles) was made to save

Maybe that was ? 42 ? - been a couple of years since I sat on a committee that discussed and designed that long range stuff for automotive.

Mart> We are in the process of switching to ? 72 ? volts IIRC.

I too think it's 42 volts that we'll see soon. Remember that it took from the 1920's to about 1974 or 1980 to get electronics into cars except for the radio (and Cadillac's photomultiplier headlight dimmer). I heard that, along with 42 volts comes a combination starter/alternator built into the auto's flywheel. And electrically operated valves. One other big gain for higher voltages is that you loose less power in the wiring, particularly for the starter.

Pete Stanaitis

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Ivan Vegvary wrote:

I think one of disadvantages of higher voltages is that it could be getting into the region where it would be a shock hazard under some conditions. Another is that even 24 volts is getting into the arc welding region where arcs are more likely to be sustained and more difficult to extinguish.

A relative who is a Ford mechanic indicated that Ford has plans to use a high power 42-48 volt flywheel alternator and drive all accessories electrically, thus eliminating the belt drives. As an aside, the early Ford Model T used a flywheel alternator.

Don Young

Which is why the 42 volt (36 nominal) system is being proposed instead of a 48volt nominal (54 volt charging) system.Anything over 40 volts (or is it 42? somewhere real close anyway) is no longer "low voltage" and ends up regulated much more stringently. I know 48 volt DC switches tend to have a short lifespan unless properly designed with arc blowout or VERY fast snap action. The advent of solid state high-power DC switching is making the 36/42 volt system almost feasible today.

And this is when the hood will only open for the manufacturer certified technician. Gerry :-)} London, Canada

That big gain comes with an interesting drawback...

Richard

I read it was going to be 48 volts

Gunner

there are a several reasons:

1. light bulbs - as you increase the voltage, filaments get thinner. Thin filaments cannot survive the vibration in a car for very long. Switching to LEDs which is happening now will eliminate this constraint, but it was in place for a long time
2. inertia - there's a lot of 12V stuff, costs $$ to change over
3. safety - above 24V, the electrical safety requirements are much more stringent
4. cost - relative cost of batteries and wire
5. other, such as cold starting versus jump starting, accessories, spare parts, etc

All real good questions, Clare.

Wish I had a valid answer or two...

If you think THAT is dangerous, how about this? My neighbor is a volunteer firefighter. He recently told me that (at least some) of the new hybrids have 300 or 400 volt systems. They have been trained NOT to go near one of them that has caught fire or even put water on them for fear of being electrocuted! ----"Even if you hear then screaming", he says. So, to me, 42 volts doesn't sound that bad. Hey, what do you think of having 120 volts and 240 volts running around your house?

Pete Stanaitis

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cavalamb himself wrote:

POSSIBLY: The NEC limit on "safe" voltage level. ????? ...lew...

OH MY GOD!!! Not a "Dynastart" like my NSU Sport Ptinz had. :-) ...lew...

Isn't the NEC limit 30 volts? ...lew...