Is an original Model-A Generator capable of 12 volts??

[Mike V. Florida]

Originally Posted by diomed

but I'm concerned that if I get stuck in traffic at night that the car will die.

At an idle and with the light on, what does the ammeter read?

The battery will last a long time with a couple of amp draw. Ever forget and leave the lights on in your modern car for an hour or so?

[diomed]

Originally Posted by Mike V. Florida

At an idle and with the light on, what does the ammeter read?

The battery will last a long time with a couple of amp draw. Ever forget and leave the lights on in your modern car for an hour or so?

It draws slightly over 10amps idling with the headlights on. Maybe 12amps??

A few years ago I was in the Hot August Nights cruise with a car we converted to EFI (Not a Model A) and it died because the battery ran down. It was an ordeal getting it out of the cruise and restarted. Maybe I'm still a bit gun shy from that trauma, haha

Sent from my A0001 using Tapatalk

[Tom Wesenberg]

The stock Model A won't be so voltage sensitive as an engine with EFI and a computer.

My 28 is all stock except I have an EVR inside my powerhouse generator. At idle the ammeter stays on zero with the stock lights on. If I also step on the brake then it dips to about -5. This is fine and my junkyard battery is still working fine even though it's over 12 years old.

[Mike V. Florida]

Ok, lets get a little technical, Reserve capacity of a battery is the number of minutes a battery can maintain a useful voltage under a 25 ampere discharge. A new NAPA 7244 battery has a reserve capacity of 130 minutes. If we were to say your battery is 25% as good as that it will supply 25 amps for 32 minutes. I hope you are not stuck in traffic at night, idling for more then 30 minutes.

[Mike V. Florida]

Originally Posted by Tom Wesenberg

The field coils only supply the magnetic field for the armature, which supplies the generator output. The stock Model A long generator fields have about 1.5 ohms and draw about 4 amps current at 6 volts.

I haven't worked with the replacement 12 volt field coils, but would guess they have more and thinner wire to keep the amp draw about the same as the 6 volt fields. I just looked up field coil draw in my 1962 Motor's Manual for Chevrolet, and both the 6 volt generator and 12 volt generators show the same amp draw.

In theory as the current in the windings increases so does the magnetic field. This field can hit saturation and no more will change at the output. As you say Tom the windings would have thinner wire and more of it to increase the resistance and maintain the same magnetic field. And since a generator really does not have a output voltage it's self, the battery or external regulator determines the output voltage. The 12 volt windings would keep the generator running within it's design parameters of current and heat.

But the Model A generator never went to school and does not know all this theory stuff and will work anyway.

[Kurt in NJ]

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Used generator bought for it's perfect rust free case ---happily making 4 amps on 6V, after 10 min of working the thermocouple placed between the case and field winding stabilized at 120 degrees (blue wire)

Flip the switch on the machine to 12V, charging rate went to 20 amps, 18 volts, in 30 seconds the temp was 160 and climbing ---I ended the test because I didn't want to damage the internals ---there is a button on the machine that momentarily dissconnects the battery for a cutout test, then voltage pegged at over 40

The 12V battery I had on the machine was not a good one and has a part in the high voltage

the field was 4 amps on 6V, 8 amps on 12V

I have been using quartz halogen bulbe for 15 years now(6V, 35watt), I never worry about the discharge with the lights on, the car can sit for months, I take a 2 hour night drive---then sits for week, then 1 hour parade at idle(not charging)with a lot of horn use---then could sit for weeks, then perhaps 40 mile daylight drive----if I take long daylight drive (100 miles)sometimes I use headlights some of the time to prevent overcharging---I don't worry, it always starts ----remember, the owners instruction book says--there will be a discharge shownig on the ammeter at idle and when driving with the lights on

[BRENT in 10-uh-C]

Originally Posted by Milligan's A Shop

This may be the easiest answer to 6 volt and 12 volt. I've worked with Powermaster of Knoxville and they have brought out a 6 volt alternator and a 12 alternator that look like a Model A generator.

Before I get too excited, ... Are you saying the Powermaster alternator just looks like a generator, ...or that it looks like a Model-A generator? The PowerMaster ones I have looked at look like a 'generic' Delco-Remey generator off of a '57 Chevrolet. Have they come out with something new that is the same length and diameter as the Model-A generator?

[Jeff/Illinois]

Called on a '36 Ford pickup years ago for sale that the owner 'converted' to 12V. All he did was put a 12V battery in the truck.

The results were 'electrifying' Fried the (original already frayed) wiring on that baby big time even started a fire under the dash! He couldn't understand what had happened. Toasted a good set of original gauges too.

[eagle]

Google the difference between a current regulated generator and a voltage regulated generator. The model A uses a current regulated generator. Will charge a 12 battery just fine, adjust your 3rd brush according to the current output you want, or install a voltage regulator if you wish.

[marc hildebrant]

Eagle,

The Model A original generator was designed to be a constant current device. However, the generator needs a lead-acid battery connected to make it constant current.

Also, the generator's internal design made it possible to keep the current "constant" with different motor speeds.

A true current regulated design today would use solid state devices to vary the field current to keep the current constant with different motor speeds.

Marc