Philippe;
I don't have a manual for the 57, but in 1958, the generator was rated at 30
AMP at 1800 RPM. That would mean that when the car was new, you would be
able to drive with the headlights and other normal loads on at around 30 MPH
or more with the generator just about making up for the total loads on the
battery, in other words, the ammeter would indicate in the center of the
gauge, perhaps slightly above that for higher speeds. Slower speeds would
cause a discharge, and lower total electrical load, such as daytime driving
with no heavy accessory usage, should show a slight charge on the ammeter.
The generator system was not expected to show any charge at idle, in fact
the specification is for only 6 A of charge at 950 RPM, this would just
about make up for the engine's draw.
Other than your car's ammeter being off center (probably due to some
mechanical damage to the movement), your car sounds about normal to me. If
your battery is staying up without need for frequent recharging, I think
you're getting about all you can expect from this system.
Your generator is not really able to keep up with ALL the cars systems on at
once, and if you drove that way for hours, with the AC, Lights, and other
heavy loads on, your battery would slowly discharge, although as it does,
the charging rate would increase so that you wouldn't be in danger of having
the engine quit. The engineers designed the car for an average mixture of
operating modes, so that on average, it will maintain the battery in a
healthy state.
I remember in the 50's having to be careful as I drove my 48 Nash between
Boston and Philadelphia in the winter months late at night, which I did
every weekend (girl in PA, school in Cambridge), as my generator really
couldn't keep up with the high beams, windshield wipers, heater and radio
for the 8 hours or so of the trip. I had to turn off the radio and sometimes
the heater, when the traffic kept me from driving over 30 MPH or so, to keep
the lights from getting dim.
The reason you see a higher charge rate when you first start the engine is
that the battery is slightly discharged by starting the engine, making the
battery voltage lower than normal. The reason the charging rate comes down
quickly, after you start the engine is that your battery is coming back up
in voltage so that the regulator is reducing the charging current.
There is always a slight charging rate when the engine is running, if there
are no electrical drains, just to keep the battery all the way charged, and
to compensate for the loads that don't register on the ammeter (like the
power windows, seats, door locks, horn, convertible top motor), and thus
there is always a slight charging current required to keep the battery up.
If the system was overcharging your battery, you'd find the battery using
too much water, and you might smell a "rotten tomato" odor under the hood
from the escaping hydrogen gas.
Dick Benjamin
----- Original Message -----
From: Philippe COURANT <accf_clb@xxxxxxxxxxxxxxxx>
To: <mailing-list@xxxxxxxxxxxxxxxx>
Sent: Monday, April 29, 2002 1:57 PM
Subject: IML: amperemeter reading (to Dick ?)
> Hi,
> As i speak of electrical devices as starter, i've another
> question about the dash amperemeter (battery is fully charged).
> On my car, with battery posts removed (or with "ignition switch
> off") the amperemeter needle is not on the "0" mark but rather on
> the "1/4" mark toward C(harge). Perhaps i've a little disturbed
> the adjustement when i removed it but itsn't the question. So on
> my car 1/4 = 0 = no current
>
> - When the engine is running at iddle the needle goes a little
> higher toward "C" (around 1/2) then at a determined speed (1000
> to 1500 rpm) goes back between 1/2 and 1/4.
>
> - If i increase the engine speed ( or if i drive at 60 mph) the
> needle is around 1/2 C or higher.
>
> - If i put headlights "on" or wipers or heater blower or AC, the
> needle comes down 0 or a little toward D(ischarge), depending of
> the electrical load and the speed of engine , i think it's
> normal.
>
> But why the needle is always higher than 1/4 (= 0) when i don't
> use some electrical devices. Does that mean that the current goes
> always from battery to generator ?
>
> --
> Philippe COURANT (Pau, France)
> Imperial 57 Crown convertible
> Buick 58 Roadmaster sedan
>
> - American Car Club de France (ACCF) : http://www.accf.com
>
> - Chrysler Imperial France : http://www.ifrance.com/c-i-f
>
> - Cadillac " Standard of Excellence " :
> http://www.ifrance.com/accf-cad
>
> - SportsCars : http://www.ifrance.com/accf-sprtcar
>
>
>
>
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