Model A Charging Conditions

Tom Cavallaro

Tom Cavallaro

Senior Member
Just wondering if I can keep the battery up under normal daylight driving conditions. At the cutout, I'm at 7.2 volts, at the battery I've got 6.9 volts, and at the Amp meter I'm reading 6.5 amps. Assuming the amp meter is accurate. Does this sound like all is fairly good or should I raise it up? Without some input, I'm afraid to cook the battery.
Thanks in advance.
Tom
 
With a rebuilt original generator ours reads a little under 10 amps driving down the road. Never a problem keeping battery fully charged. Drops to around 2 amps with the head lights on. Enjoy.
 
I'm running about 8 amps charge at cruise speed. I haven't double checked it with my Fluke ammeter, but the Fluke and my dash meter do run pretty close (last tested together about 3 years ago).

Three years service so far using a new (then) Interstate 6v battery. 99.9% daylight driving. No issues to report.
 
Tom Cavallaro said:
Just wondering if I can keep the battery up under normal daylight driving conditions. At the cutout, I'm at 7.2 volts, at the battery I've got 6.9 volts, and at the Amp meter I'm reading 6.5 amps. Assuming the amp meter is accurate. Does this sound like all is fairly good or should I raise it up? Without some input, I'm afraid to cook the battery.
Thanks in advance.
Tom
Click to expand...
If you are driving on long trips I would move the third brush in an opposite direction of rotation to 2amps to avoid cooking the electrolyte out of the battery.
 
The generator's charging current is determined by headlight usage. Ford recommended 6A to 8A for summer driving and 10A to 12A for winter driving.

The generator's output is adjusted by moving its 3rd brush.

The cutout switches the generator into & out of the electrical system to prevent the generator from drawing current from the battery.

The cutout connects the generator when its armature speed produces 7V to 7.5V which assures that the generator is producing a higher voltage than the battery. This generally occurs at about 700RPM to 750RPM of the generator. Recall that the generator turns at 1.5 times the engines RPM.

The cutout disconnects the generator when the generator's output is less than the battery's voltage, and the discharge current at the ammeter is 0 to 2.5A.
 
As mentioned, the cutout is merely a switch.

Charge rate kinda sorta depends on your driving style. If the majority is daytime then 2-3 amp charge rate is fine. If the majority is at night then bumping it up to 7-8 amps would be fine as long as the battery level is looked a little more often.

The charge rate is easily [ generally] changed by moving the third brush [ under the generator band].
 
Also, if you make shorter trips, with more frequent starts, you will need a charge rate higher than 2A. When I drive I usually take short daylight trips of about 3-5 miles, that's why I set mine to about 7-8 A.
 
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