Re: Alternator Dynamics

["Christian Els" <tiAn@usiw.net>]

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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> >>
> >
> >
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