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Rob Spiegel
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Blogger
Greater potential shocks
Rob Spiegel   3/20/2012 8:13:05 AM
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I would imagine the high voltages would also come with higher potential safety problems. I would imagaine the higher voltages could be an issue in collisions.

Alexander Wolfe
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Re: Greater potential shocks
Alexander Wolfe   3/20/2012 9:05:18 AM
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Your imagination is correct, Rob. Even in non-accident situations, the use of higher voltages adds an additional layer of engineering, as Chuck points out, in the form of isolators. Supposedly, a high-voltage isolator fault was at issue in the recent Fisker Karma car which "died" when it was brought out to Consumer Reports's test track.

trawickim
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Iron
BMW's Percussion disconnect for Z3
trawickim   3/20/2012 10:56:25 AM
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The BMW 2000 Z3 already has the answer to post accident power removal  with percussion connector at positive battery post.

The unit is designed to fire and disconnect battery source upon deployment of airbag from accident.

Sehr gutes engineering von BMW!

 

Trawickim

 

TJ McDermott
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Blogger
Insulation too
TJ McDermott   3/20/2012 11:48:44 AM
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The cables in question will be exposed to temperature extremes (0-100 F in ambient swing alone).  The insulation of these cables will have to stand up to that, as well as engine heat, and do so for a design life of a decade or more.  No cracking or degradation of the insulation will be acceptable.

sensor pro
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Gold
Re: BMW's Percussion disconnect for Z3
sensor pro   3/20/2012 12:12:34 PM
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What would be the result of an accident if the dent is in the area of the bettery and the terminal shorts to some other part of the body of the car. ?

I'm not sure the relay will help.

Rob Spiegel
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Blogger
Re: BMW's Percussion disconnect for Z3
Rob Spiegel   3/20/2012 1:26:42 PM
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What a smart idea from BMW. I would imagine that feature is helpful to emergency personnel who have to wrangle accident victims out of cars. 

Charles Murray
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Blogger
Re: BMW's Percussion disconnect for Z3
Charles Murray   3/20/2012 7:44:28 PM
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Interesting...thanks for the heads-up, trawickim.

rdthybrid
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Iron
HV
rdthybrid   3/21/2012 9:45:14 AM
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In developing hybrid construction equipment, inverters are now using 800 VDC capacitors and the bus takes several minutes to reduce to a voltage that isn't deadly.  So, future accidents are highly likely.  However, you can't force a new technology without hazards especially when consumers need the new product to perform to the exact same specification as the traditional product.

Pete Ostapchuk
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Iron
Re: BMW's Percussion disconnect for Z3
Pete Ostapchuk   3/21/2012 10:45:33 AM
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Trawickim had some interesting observations. The safety feature that disconnects the battery reminds me of the fuel pump shutoff switches on some cars. Even the 12 Volt batteries should have some means of disconnecting. I'm reminded of a car fire that was extingushed only to reignite because of a short in the wiring. The fire extinguishers ran out before the battery did and the car was a total loss. Some industrial machhines have an emergency stop button that kills all the power. If you adjust the nuts and bolts on your battery connectors, you can push them down onto the battery post with a twisting motion and they will lock into place. You can also pull them back off in case of an emergency. If you have side posts, oh well.      Pete O. 

D. Sherman
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Gold
History and safety
D. Sherman   3/21/2012 11:17:26 AM
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I realize the article is about the shift to higher voltages in automotive electrical systems, but the "history" portion at the top of the article makes no sense at all, particularly this line: "When the battery alone wasn't powerful enough, engineers augmented it with an alternator and a fan belt."

There was never an automobile that included a battery but provided no means to charge it. Some very early ones had a magneto for the spark, a hand crank for starting, and carbide lamps for headlights, but as soon as the magneto was replaced with a coil-and-points ignition system, a generator was needed to charge the battery. In fact, some early vehicles had generator-driven electric lights before they had an electric starter or a battery.

Also, if one is writing a brief history of automotive voltages, it should be mentioned that all military vehicles since about 1950, and some heavy civilian vehicles throughout that time period, have used 24 volt systems for exactly the same reason higher voltages are being used today -- to reduce the amount of copper needed to carry high power levels.

As far as the safety issues go, I think the only way we're going to get anywhere without prohibitive expense and inconvenience is if we accept that the standard of comparison be "no more dangerous than a tank of gasoline" rather than "can't possibly be hazardous under any circumstances".

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