Re: Alternator Dynamics

["Wing Gee" <winggee@hotmail.com>]

Ok i understand it a bit better now.

Wing
----- Original Message -----
From: "Christian Els" <tiAn@usiw.net>
To: <aaron@makuta.com>; "'Scirocco LIST'" <scirocco-l@scirocco.org>
Sent: Thursday, September 07, 2000 10:23 AM
Subject: Re: Alternator Dynamics


> EVERY component should draw less than the rating on the fuse protecting
it,
> or you will replacing fuses like crazy.
>
> The PTB (powers that be) select a fuse rating based on the peak momentary
> capacity of a component to withstand some current. For example (all
numbers
> pulled at random from my anterior dorsal cavity --please don't work from
> them), the wiper motor requires 6 amps to start spinning, about 0.5 amp to
> run and about 3 amps to reverse (linkage) directions. It was determined
that
> 10 amps to the wiper motor would fry it, so they mandated an 8 amp fuse to
> allow it to work without posing a risk to itself or the rest of the car.
>
> The capacity of the alternator is ideally a little more than the
> simultaneous peak draw on the system from all ancillary electrical
> components. Running down the road, you should not be using most of its
> possible output or you will put your alternator into a tune-up replacement
> interval and it will not last the lifetime (+/-) of the car.
>
> Natch, bolting up as high-output alternator as will fit is cheap
insurance,
> especially if you have a whomping stereo and a rack of driving lights on
> your car. Most of the time you won't be working the motor any harder as
you
> aren't drawing anymore current, and when you do need it, you don't
> (over)stress the alternator.
>
> Cheers,
>
> Christian
> 87 16V
> stuff...
>
>
>
>
> ----- Original Message -----
> From: Aaron Ness <aaron@makuta.com>
> To: <photo@intrex.net>; 'Scirocco LIST' <scirocco-l@scirocco.org>
> Sent: Thursday, September 07, 2000 11:50 AM
> Subject: RE: Alternator Dynamics
>
>
> Not sure about the others, but the wipers are fused at 8A.  I would expect
> them to operate somewhere below that.  Is that right, or am I confused?
>
> Aaron
> '82 Scirocco
> '84 Scirocco
> '70 Bug - Hibernating
> '87 Jeep Cherokee 4.0
>
>
> > -----Original Message-----
> > From: owner-scirocco-l@scirocco.org
> > [mailto:owner-scirocco-l@scirocco.org]On Behalf Of Bill Collins
> > Sent: Thursday, September 07, 2000 11:45 AM
> > To: Scirocco LIST
> > Subject: Re: Alternator Dynamics
> >
> >
> > Here are some numbers that I came up with, you might want to
> > modify them for your situation.  This is a worst case
> > situation, like driving at night, in the rain, with the A/C
> > on for defogging (not unusual here in the south!)
> >
> > Fuel pump      10A
> > Radiator fan   20A
> > Hi beam lights 10A (that's the number of a two lamp sealed
> > beam system, the Scirocco's 4 lamp system or aftermarket
> > system may pull more)
> > Wipers          8A
> > Rear window defogger 10A
> > Misc (tail lights, ignition, etc) 10A
> >
> > Total: 68 amps! That's without a stereo, extra lights, etc.
> >
> > Bill
> >
> > ---------- Original Message ----------------------------------
> > From: Mark Peele <type53@yahoo.com>
> > Date: Thu, 7 Sep 2000 08:37:50 -0700 (PDT)
> >
> > >Here's a general question:
> > >
> > >My Sciroccos (all three) have 65A alternators. I have
> > >removed the A/C from all three. I don't anticipate
> > >having more than a 50W stereo. All cars will have
> > >relayed headlights with H-4 main beams.
> > >
> > >Under what conditions would I really need a bigger
> > >alternator (90a)?
> > >
> > >What is the advantage?
> > >
> > >Will a 90a alt. create more "drag" on the motor at any
> > >given RPM than a 65a alt.? (assuming identical demand
> > >from stereo, lights, etc.)
> > >
> > >TIA!
> > >
> > >--- Wing Gee <winggee@hotmail.com> wrote:
> > >> Just curious then, why do people make such big
> > >> altenators then if their only
> > >> going to be drawing about 20 amps or so. aren't the
> > >> corrados like 110a or
> > >> something.
> > >>
> > >> ----- Original Message -----
> > >> From: "Toby Reed" <toby@eskimo.com>
> > >> To: "Wing Gee" <winggee@hotmail.com>
> > >> Sent: Wednesday, September 06, 2000 1:36 PM
> > >> Subject: Re: Math wiz's calculating hp.
> > >>
> > >>
> > >> >
> > >> > Wing, you got it. But remember the alternator is
> > >> almost never making 65
> > >> > amps of current, so the actual drain is a lot
> > >> less. I'd say driving around
> > >> > town, you're only drawing about 5 or 10 amps out
> > >> of the alternator.
> > >> > Headlights, stereo, fan blowing and things go up
> > >> to 20 or 30 amps.
> > >> > -Rarely- will you see the max capacity of your
> > >> alternator....
> > >> >
> > >> > Mechanically the alternator gets harder to turn
> > >> when its making more
> > >> > current, so you're drawing a lot less HP than 1.21
> > >> ! Probably closer to
> > >> > one sixth of one horsepower.
> > >> >
> > >> > If you wanted to know more exact values, you could
> > >> hook up an ammeter in
> > >> > line with your alternator and get some data on the
> > >> efficiency of the
> > >> > alternator from the company that made it.
> > >> >
> > >> > -Toby
> > >> >
> > >> > On Wed, 6 Sep 2000, Wing Gee wrote:
> > >> >
> > >> > > For all you math people. See if i did this
> > >> right. I'm converting power
> > >> > > to hp. now i know P=I*V. Let me tell you what
> > >> i'm doing first. I wanna
> > >> > > see how much hp the altenator is dragging while
> > >> it's charging. Now i
> > >> > > know I=65a and V=~14v(it charges around there)
> > >> Which is then multipled
> > >> > > to get 910Watts=P. Now 1hp=746watts. now when i
> > >> divide that. i get
> > >> > > 1.22Hp. so my 65amp altenator is sucking up
> > >> about 1.21Hp. To me that
> > >> > > seems about right.
> > >> > >
> > >> > > Wing
> > >> > >
> > >> >
> > >> >
> > >>
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