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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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