Date: Thu Nov 30 15:36:03 2006 Back to Contents
Author: Dan Beeker
Subject: Re: Cars, lights, and mileage - was Re: The Inconvenient
One of the reasons automotive voltages have been kept low is the danger of
electrocution. The common value for potential electrocution is around 30
volts though it can vary with conditions, like how wet (conductive) a
person is. But with the need for greater and greater power, the safety issue
has given way to practicality. I forget who but I believe it is Chevrolet
that has had choke heaters that run straight off the alternator at around
100 volts for many years. So high voltages are nothing new. And don't semi
trucks run at a higher battery voltage? Keep in mind that technology has
improved since the first cars were made so safety is not so much an issue.
Connectors are now quite waterproof, wire bundles are factory assembled etc.
and we have electronic monitoring systems that can turn off the poer system
in event of a catastrophic accident (such as when the airbags are released).
Advantages are that wiring can be much smaller since the limiting parameter
is ohmic heat generated in the wiring and connectors. Higher voltage means
less current, hence less heating. So a smaller wire size can be used saving
costs, space and weight. It is a win win situation for the car manufacturers
as they are all for keeping the owner from working on theor cars. It is
probably a win win for the car owner as well since "no user serviceable
parts inside" means we won't be poking our hands and nosesd into cooling
fans and power steering belts etc. : )
Undergraduate Physics Lab Coordinator
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Phone: (812) 855-5903
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From: email@example.com [mailto:firstname.lastname@example.org] On
Behalf Of John Welch
Sent: Thursday, November 30, 2006 12:36 PM
Subject: Re: Cars, lights, and mileage - was Re: [tap-l] The Inconvenient
That's interesting about the 48 V. Will a 48V battery capable of putting
out many amps be a safety hazard at all?
Frank Cascarano wrote:
> A nice demo to show this is turning a hand generator with the leads
> open (very easy to turn) and then turning it with a light bulb hooked
> up (more difficult to turn).
> I read that there is a big push to develop LED headlights for cars for
> just this reason. Their lower energy consumption would add up to huge
> gas savings (a very small impact per car multiplied by a large number
> of cars). This is especially true now that most cars have daytime
> running lights.
> The same article said that the standard 12 V car battery would be
> changing soon to a higher voltage. If I remember correctly, 48 volts
> will be the standard car battery very soon.
> At 03:47 PM 11/29/2006, you wrote:
>> I think the clearest way to see the connection is to look at energy.
>> from rolling down hills, the only energy input to the car comes from
>> gasoline in the tank. That energy makes the car go, runs the AC,
>> runs the
>> generator that charges the battery, etc.
>> Of course, if you charged the battery by plugging the car into a
>> charger every night, then the electric outputs like the radio would
>> not be getting their energy from the gasoline.
>> -----Original Message-----
>> From: email@example.com [mailto:firstname.lastname@example.org]
>> On Behalf Of Anthony Lapinski
>> Sent: Tuesday, November 28, 2006 6:39 PM
>> To: email@example.com
>> Subject: Re: [tap-l] The Inconvenient Truth
>> This may seem tangential, but I've often heard/read that you get
>> better gas mileage with the radio/AC off. Can anyone explain why this
>> is the case? To me, the battery supplies energy to power the lights,
>> radio, and fans, while the gas is used (via the spark plug, etc.) to
>> run the engine. I don't fully understand the battery/gasoline
>> connection and why less battery use equates to improved gas mileage.
>> firstname.lastname@example.org writes:
>> >I drove my 1995 Lincoln Town Car almost 200,000 miles in ten years
>> >getting 20.5 miles per gallon. I always drive with windows up and
>> A/C on
>> >and often listen to the radio.
>> >I traded it in for a 2005 Lincoln Town Car that, after almost 23,000
>> >miles, gets only 19.5 miles per gallon, but the ride remains
>> >In the first instance, I had many more 600 mile trips. I often
>> drove to
>> >College Park (310 miles) without stopping, only filling up when
>> >back and not having to stop again. The convenience is great and I
>> >like the added insurance.
>> >John Hubisz
>> >Zigmund J. Peacock wrote:
>> > Taplers, I like Dave Sturms comments and agree wholeheartedly.
>> > My "two bits" is related to fuel economy, the Toyota and Nissan
>> >slightly better fuel mileage than my monster. And the small V8
>> >engines both Ford and Chevy build are more fuel efficient than any
>> offered by
>> >the Nissan/Toyota brigade.
>> > Incidentally my big engine sits home and I ride the bus to work,
>> >using my truck to tow my toys on weekends.
>> > Zig
>> >David Sturm wrote:
>> >Perhaps this discussion should occur on an alternate list from
>> >tap-l? I'll look to see to creating something on Yahoo groups that
>> >we could
>> >share since I'm not sure how Al Gore's politidocumentary affects my
>> >ability to work with physics laboratory, lecture and education...
>> >My only contribution to the thread will be to correct an extreme
>> >error presented here, because I believe it disparages the real
>> >American car industry, of which I have a number of relatives
>> >employed in...
>> >[ mailto:email@example.com ]firstname.lastname@example.org on Saturday,
>> >25, 2006 at 6:08 AM -0500 wrote:
>> >The reason Toyota as a car manufacturer does extremely well in
>> >to the economically protected American car industry is the mere fact
>> >they have been optimizing their cars for less resource consumption
>> >for decades already.
>> >I know slagging America seems to be popular, but Toyotas and Hondas
>> >and most other "so-called imports" driven in the United States are
>> >by far produced *in* the United States, and are part of the American
>> >car industry, employing American engineers, and American scientists,
>> >many of whom received their physics
>> education in
>> >our PIRA-supported classrooms... I've had cousins employed at the
>> >Honda plant northwest of Columbus, Ohio near Marysville, Ohio since
>> >the plant opened in 1982
>> >[ http://www.ohio.honda.com/ ]http://www.ohio.honda.com/
>> >It's "more American" than Ford plants in Mexico, GM plants in
>> >Canada, etc. BMW manufactures in South Carolina... Mercedes in
>> >Alabama... and the list goes on... And Daimler-Chrysler... is a
>> >German company
>> now, not
>> >an American one. And even that's
>> >really meaningless in this day and age. My stock portfolio has
>> Honda in
>> >it (NYSE: HMC), as do many of its employees in the U.S....
>> >There's no economic protection in the United States, clearly. Ford
>> >and GM's problems have to do with union contracts they negotiated in
>> >the 1960s and 1970s that gave liberal benefits to retirees until death.
>> >can't numerically sell the number
>> >of cars that supports that pension overpromising... Because they
>> >overspent on labor, they ceased putting quite as much into R&D...
>> >and make economic decisions that aren't based on supply and demand.
>> >David E G Sturm - [ mailto:email@example.com ]firstname.lastname@example.org -
>> >1.207.581.1241 --Physics & Astronomy Instructional Laboratories
>> >--Bennett Hall Lecture Demonstration Facilities
>> >--Mainely Physics Road Show
>> >Dept of Physics & Astronomy -- University of Maine
>> >5709 Bennett Hall -- Orono ME 04469-5709
>> >[ http://www.physics.umaine.edu/ ]http://www.physics.umaine.edu/
>> >Zigmund Peacock
>> >University of Utah/Physics
>> >115 SOUTH 1400 EAST #201 Tel 801 581 6602
>> >SALT LAKE CITY UT 84112-0830 Fax 801 581 4801
>> > "We sleep safely in our beds because rough men stand ready in
>> >the night to do violence to those who would do us harm"
>> > -- George Orwell
>> > "All that is necessary for the triumph of evil is that good
>> >men do nothing!"
>> > -- Edmund Burke
From email@example.com Thu Nov 30 15:36:03 2006