One of the major problems with anything relating to entertainment is a real
inflated sense of what they are delivering. I'd never accuse them of lying,
but on the other hand I'd be extremely surprised if any of the 100 watt
amplifiers delivered anything close to 100 watts.
On another note the math below is incorrect. Assuming that the amp in
question really delivers 100 watts output and that it is 75% (a reasonably
optimistic view) efficient this means it takes over 133 watts. Converting
this to required current gives 10.1 amps (assuming a terminal voltage of
13.2VDC). Given that audio is never continuous the peak current is probably
closer to 20 Amps at any given instant this depends on the ratio of highs to
lows (highs take more power than lows).
Remember these are the same folks who bring you that 6Hp compressor that
runs on a standard 15 amp 120 outlet.
Having said that I'd put the largest deep cycle battery that'll fit in the
car and let the stock alternator run it. Just don't drive to long after
dark
Just my two cents worth (well maybe .075 cents worth)
Steve
tr6@kc4sw.com
-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net]On
Behalf Of Andrew Packard
Sent: Sunday, October 20, 2002 8:12 PM
To: 'R. Ashford Little II'; 6-Pack; Triumphs@autox. Net
Subject: RE: Alternators and Radios
The Ford Fiesta Bosch alternator has a 55 amp rating. The installation is
incredibly easy. I just had to get a slightly shorter fan belt and shave a
bit of the mounting bracket to allow for the alternator fan blades to clear
it. Even the plug from my Lucas pushed right into the Bosch. I would think
that 55 amps would be enough to run about any reasonable stereo set up you
would want.
Andy
TR250
-----Original Message-----
From: R. Ashford Little II [SMTP:ralittle2@mindspring.com]
Sent: Sunday, October 20, 2002 5:26 PM
To: 6-Pack; Triumphs@autox. Net
Subject: Alternators and Radios
I've got the stock alternator or my 70 TR6. I'm thinking of upgrading
the stereo to add an external amp to my CD player, however, I'm a bit
worried that with my stock setup it's not such a good idea. I also lack
almost all skills related to electrical so I'm turning to those my DC
inclined. I was given this example and would like to know if this is a
good rule of thumb?
Let's say that you have an amp rated at a total of 100 watts (either
25x4 or 50x2). To get the estimated draw you would take the 100 and
divide it by 14.4 which yields 6.94 amps. Is this correct? Also there
is supposed to be some efficiency loss in the amp so I was told that you
would really take something like 100 x .75 (25% loss due to heat) =
75/14.4=5.21 amps.
All amps, just like anything, are not created equal either. You can buy
an el cheapo model that supposedly rated at X rms per channel vs. brand
B which is a true reflection of their advertised power. How do you
figure that in?
What is the estimated draw of the lights and blower when on? This will
give me an idea of how much excess I'm dealing with. Also, this looks
like it might necessitate an upgrade to the Ford Fiesta alternator.
What's the output of that again?
The last thing I want to do is to purchase something that ends up
working beautifully, but prevents me from hearing the truly melodious
sound of my engine.
TIA,
R. Ashford Little II
www.geocities.com/ralittle2
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