FW: Fuse Amperage??? for a fuse between the battery and the car.

[Richard J Lebens]

This is an interesting question.

Doesn't a starter motor present pretty close to a short to the battery
(600 amps limited by the source impedance of the battery)?

Won't a fuze this size let 3-4 times it's current rating through for
several seconds before it melts?  Does this mean with a 175 amp fuze
you can crank your car for 5 seconds at 600 amps but it blows after
that?  Will it interrupt the fault before the energy in the battery is
depleted?

What is the resistance of your rear seat springs and associated
fittings?  How much damage will your prevent with a fuze in series?
Will a fault blow the fuze(what is the resistance of the fault)?

In our litigious society why aren't they standard equipment on all
cars?

--- "Livolsi, Stephane" <Stephane.Livolsi at investorsgroup.com> wrote:
> I have to agree with Marc.  When your battery shorts, I think that
> all 400
> or 600 or whatever amps available try to go through, which would
> definitely
> blow a 175 amp fuse.  Whatever current goes through the starting
> circuit is
> limited by the starting motor itself and that is well under 175 amps.
>
> I think that you can almost weld sheet metal with the arc created by
> a
> shorted battery .....(let's not ask how I know this, ok folks  ;)
>
> .02
>
> Stephane
>
> > ----------
> > From: 	Marc Swanson[SMTP:mswanson at sonitrol.net]
> > Sent: 	July 30, 2002 10:11 AM
> > To: 	Richard J Lebens
> > Cc: 	quattro at audifans.com
> > Subject: 	Re: Fuse Amperage??? for a fuse beween the battery and
> the
> > car.
> >
> > > Are you asking about a fuze on the battery?  When you are
> starting your
> > > car the battery is delivering all the power it has for as long as
> the
> > > switch is on. The starting circuitry is a very low impedence,
> similar
> > > in magnitude to your seat springs connected to ground.
> >
> > agreed that it is a high current draw, but not that high!
> > Under full load of starting the 175 amp fuse won't blow, but.. say
> if
> > your main battery feed line chafes against the body and shorts to
> > ground.  That would start a fire without a fuse in place.  That
> would
> > certainly be a significant enough draw to trip the 175 amp fuse.
> >
> >
> > Later
> >
> >
> >
> > --
> > ----------------------------------
> > Marc Swanson, Software Engineer
> > Sonitrol Communications Corp.
> > Hartford, CT
> >
> > Email: mswanson at sonitrol.net
> > Phone: (860) 616-7036
> > Pager: (860) 948-6713
> >  Cell: (603) 512-1267
> >   Fax: (860) 616-7589
> > ----------------------------------
> >


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