Kinderlehrer's wrote:
> Ok, now I'm very confused. The output of the alternator is dependent on the
> rotation speed of the armature, ie RPM of the engine.
> I put an electric fan in the car, then I have to go faster to get more
> horsepower to the fan motor??
Not really. Most of the time, there is current to spare. The
battery will be fully charged, all accessories can work, and the
alternator has excess capacity. LUCAS alternators have
low output, but British cars tend to have few accessories
so it works out.
Running a fan isn't likely to put you over a limit unless you
are too close to it anyways.
My modern car has an electric fan that only comes on
when required. I almost never hear it on. The only time it
comes on is at idle. I often hear it when I get out
of that car to jockey spots with my LBC. I have an inline
parking spot, so as I am starting up the Midget I
often hear the idling Celica start it's fan behind me.
So when you calculate your current demands for the fan,
you want to be able to run it often but in all likelihood
you won't.
> I guess I'm lucky because I have a TR3 with a generator which is far less
> than 100% efficient. It keeps on turning even after the battery is charged
> up and it isn't really needed, so I can use those wasted revs to drive my
> electric fan (when I get one).
The generator suffers from the same problem, just at
a greater level. Not only does the generator produce less
current, but it also often requires higher RPMs to do so. Often
while idling the generator cannot help at all
because the regulator will not get enough juice from the
generator to complete the charging circuit.
Your TR3 has an ammeter, so you can watch the effects
of various conditions. If your ammeter is below zero,
you are losing the battle. Unfortunately idling is
when the fan is needed most and there is the least
current to drive it.
--
Trevor Boicey
Ottawa, Canada
tboicey@brit.ca
http://www.brit.ca/~tboicey/
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