6V to 12V conversion

1931 flamingo

1931 flamingo

Well-known member
Good, bad, correct NOT the intention of this Post.


In the latest issue of Street Rodder magazine is a detailed (with pics) article on how to convert a stock 6V Model A to 12V. It may not be totally accurate but interesting IMO. FWIW
Paul in CT
 
I haven't read the article in Street rodder magazine . Converting the model A from six to twelve volts is really simple . The voltage of the battery that is used controls the voltage . To make things simple and appear original , I use the original unmodified generator with a Fun Projects TWELVE volt voltage regulator that mounts in place of the cut out with no mods needed for the generator. There is a difference between the six volt and the twelve volt Fun Projects voltage regulator . If the car will be used with positive ground , No mods to the original wiring will be necessary . The generator charges the battery in amps and I adjust the adjustable third brush in the generator for a maximum charge rate of ten amps . The voltage regulator allows the generator to charge on demand . In other words the generator won't charge maximum rate except when needed for the lights or other higher draw accessories . It will be necessary to either use a ballast resister at the coil or change the coil to a three OHM version for a more original look . I have run unmodified six volt model A starters on twelve volts for fifty years or more on some of my model A's with no problem . I have used GOOD original starter drives on twelve volt but it is probably best to use the modern starter drive . Old worn starter drives can fail on either six or twelve volts . Of course all of the bulbs plus the battery will need to be changed to twelve volt . Any six volt accessories will need a ballast resister . If a lot of high draw accessories are used it would be best to use an alternator . The alternator can charge higher amperage as needed with modern cars with higher draw accessories . Most of the model A parts catalogs list a one wire connection alternator to take the place of the generator .
 
12v conversion using an alternator means smooth constant voltage,your electrical components will last longer,the parts are cheaper and most modern conveniences are configured for 12v.For a touring car its hard to beat.
 
There are lot of us who have changed to 12V using the original generator and have had good results. The battery acts as a large capacitor smoothing out the impulses from the commutator of the generator. The alternator may produce a little smoother 12V, but do the other electrical components care?
 
The other components don't seem to know the difference or care . The generator should have an easier life on twelve volts and a lower maximum amperage output . I use the original type 20 amp ammeter . With this setup the maximum charge rate is set for a maximum 10 amp charge . I use the halogen headlight bulbs that fit the original sockets and they are plenty bright , with the generator brush set for a maximum charge rate of 10 amps . I use the 35/35 W 12 volt bulbs
 
12V with a negative ground is beneficial for employing modern electronic devices in a Model "A" such as a cell phone charging port, GPS and other devices using a USB port. I have a 12V accessory power panel in my "A" that is held in place with commercial Velcro.
 

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To change the polarity from positive to negative ground it will be necessary to reverse the connections at the coil , ammeter and battery to negative ground . It will also be necessary to flash the cut out . I use a short piece of wire and use it to jump between the terminals on the cut out to flash the cut out and complete the change from positive ground to negative ground .
 
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Which issue of Street Rodder. I looked through mine and could find the article you described (Aug, Sept, Oct)
Thanks Brian
 
Many folks may not know that a 12 volt system amp draw is half of a 6 volt. Since our wiring was gauged for 6 volts and twice the amperage you end up with a heavy duty wiring harness... For touring an Alternator does a great job and hallogen headlights and LED tail and turn you are ready for some wonderful evening cruises with you better half!

I also recommend a modern bedix There is a lot more torque hitting it on 12 volts which can shear bolts. Easy mod. buy only the US made one however.
 
I wrote the story using my '30 coupe as the guinea pig. What part did you find "not to be totally accurate"? Just hoping to clarify if something came across as vague.

Very happy with the 12 volt upgrade as well as the Pertronix conversion. The car fires right up, without using the choke, which was something it never did before. Bright lights, a reliable alternator, and I was able to move the battery under the seat. Win-win for me.

-Ryan
 
I am just wondering what would have made it so the choke would not be needed. Maybe when the weather turns cold again, you might find that it still needs to be choked.
 
Surprised me as well. When I first bought the car, I drained the battery trying to start the car as it required a precise balance between choke, throttle, etc to get it to fire off. Eventually I figured out the required dance and could get it fired first crank.

Speculation says hotter spark and faster cranking is responsible. That's what I'm leaning towards. I completed the upgrade over the winter so warmer weather wasn't around to help.
 
I do not know what the fuss is. The car was designed for six volts. American cars were 6 volts for decades with no problem. My car remains six volts and it runs fine.

A bigger concern is fuses. I have wired my car for separate fuses on separate branches.
 
Penthode said:
I do not know what the fuss is. The car was designed for six volts. American cars were 6 volts for decades with no problem. My car remains six volts and it runs fine.

A bigger concern is fuses. I have wired my car for separate fuses on separate branches.
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While European cars were 12 volts from very early, even 24 volts, I am told. It took a LONG time for American manufacturers to get out of the 6 volt rut. Now that they have, can anybody imagine them going back to 6 volts?
IMO, this is like the discussion about oil and air filters. It is modern practice and won't be going away in a hurry because the benefits are too great.
 
I can't think of a single advantage for running any vehicle on six volts. Six volt systems run higher amps . Higher amps cause heat and shorter component life. Six volt systems have less cranking power , dimmer lights plus six volt parts and components are getting harder to find . Most cars have used twelve volts systems for over sixty years . There were several good reasons .
 
Purdy Swoft said:
I can't think of a single advantage for running any vehicle on six volts. Six volt systems run higher amps . Higher amps cause heat and shorter component life. Six volt systems have less cranking power , dimmer lights plus six volt parts and components are getting harder to find . Most cars have used twelve volts systems for over sixty years . There were several good reasons .
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You may already know this, but here goes anyway.


There is at least one exception to this, the Model a Coil. The 12V Coil actually has to dissipate more power than the 6 V Coil. And some would rather use a 6v coil with the series R to keep coil power dissipation down.


6V Coil, 6 Volt battery - (Volts)6 V /(Resistance)1.5 ohms = (Current) 4 amps
(Current) 4 amps X (Voltage) 6 Volts = 24 (Watts, Power)


12V Coil, 12V battery - 12 Volts / 3 ohms = 4 amps
4 Amps X 12 Volts = 48 Watts


Even though the coil is not on 100% of the time, the 12v coil has to dissipate twice the power of a 6 Volt coil, which can shorten the life of a 12 V coil since it is in the same power dissipation package as the 6V coil.


On a 12 Volt system some use a 6V coil with a series resistor, and the power dissipation is then shared equally by the coil and the series resistor. This drops Coil Power dissipation to 24 Watts.
 
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