6v to 12v question

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
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David V
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Re: 6v to 12v question

Post by David V » Wed May 16, 2018 9:06 am

Wolfman wrote:
Wed May 16, 2018 3:54 am
The output from a 6 volt generator is most likely not going to get high enough to close the contacts on the cut out relay or activate the electronics in the 12 volt regulator so the generator is never actually connected to the 12 volt battery. It just keeps the fan belt tight.
In your jeep, you need something that keeps the battery charged. 6 or 12 volt.
It doesn't just keep the belt tight. Surely it charges the battery through the regulator. No ? So if a 6v 40A gen produces half the amperage in a 12v system it must be producing 20A. And the 12v gen produced by Autolite produced 25A. That's not so far off.

Also I imagine that the gen is producing current all the time and it's the regulator that cuts off the current if the battery is charged. So I don't think the gen will cook itself.

I've ordered a good battery so I will fix it up next week if I can find the time and see what the voltage level across the battery/gen is.

Plan B - the alternator...

Wish I'd paid more attention to this at school !
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Re: 6v to 12v question

Post by conrod6 » Wed May 16, 2018 10:31 am

6V produces twice the amperage not half .

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Re: 6v to 12v question

Post by Wolfman » Thu May 17, 2018 4:55 am

Back to square one and your original question, David.
You have a jeep with a 6 volt gen. ( dynamo) and starter, with a 12 volt battery. The way it was when you got the jeep.
Is it OK to run it on a 12 volt battery ?
Yes. You will need to change the lights to 12 volt and add an ignition resistor to the 6 volt coil or change the coil to 12 volt, if not changed already.
The starter and generator will not burn up but the 6 volt generator will not charge a 12 volt battery. Even if you have a 12 volt regulator. Keep a battery charger handy.
If you want the battery to stay up while driving, you will need to change the generator and regulator to 12 volt. 12 volt alternator is an option.
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Re: 6v to 12v question

Post by OldPappy » Thu May 17, 2018 11:05 am

Someone asked a few posts back:

"I took my second starter apart years ago to replace the bendix and cannot get the bushes back in. It's been sitting in a box in pieces ever since.
How do you do that ?"

It has been about 30 years since I was into one of these old Jeep starters, so not sure this is helpful, but most starters have a little hole in the recess for the brushes. That hole is so you can push the bush down compressing the spring, and insert a pin into the hole to hold it in place. I think these have that same feature, but like I said it has been a long time since I rebuilt one of these old starters.

If the hole is there, you install the new brushes, push them down, insert a straight pin to hold them down, install the armature, and then pull out the straight pins.
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Re: 6v to 12v question

Post by Wolfman » Fri May 18, 2018 6:31 am

No holes. You are thinking, maybe , of Delco alternators. There is a hole in the brush carrier on those, a pin goes through to hold the brushes up until the body is assembled. Then the pin is removed out the back.
Starters, there are different flavors.
When the brush carriers are in the field housing on spring loaded arms, it is like wrestling with an octopus, or there is a cone shaped tool that fits on the armature shaft. As the field housing is installed, the cone piece pushes the brushes out so they slide over the end of the commutator.
When the spring arms are on the end cap, start the cap on on a bit of an angle. Get one brush on the commutator, then carefully work your way around, one brush at a time until you get the others on and push the end cap into place. Takes practice.
When the spring holders are on the end cap and the brushes are in rectangular holders with flat coil springs pushing down on them, pull the brushes out of the holes in the side of the field housing, leaving them free floating. Install the end cap. Then, working through holes, pull the flat coil spring up with a hooked tool and insert the brushes in their carriers, one at a time.
One more but this is for small engine starters. I'm on a roll.
The brushes are in spring loaded carriers in the end cap. There is a large flat fiber washer that is inserted in the center of the brushes to hold them out. Once the washer is in place, holding the brushes into the carriers, the end cap is carefully pushed into place. As the cap slides into place, the commutator pushes the fiber washer back against end cap. By the time the washer is back and the brushes are released, they snap out against the commutator.
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Re: 6v to 12v question

Post by OldPappy » Fri May 18, 2018 7:53 am

Probably thinking of something Chevy, as I have had a number of them from the 50s. Could have been an alternator, or generator of some kind.
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Re: 6v to 12v question

Post by Marty, SoCal » Fri May 18, 2018 9:59 am

About six months ago I converted a buddy's MB to 12 volts, he was running it on 8 volts and didn't want to go back to six volts. I used the stock 6 volt generator and a 1964 12V Ford civilian voltage regulator. Switched all the bulbs and the coil, too. (The fuel gauge has been dead for a long while, we'll address that soon)

The main difference between the 12 and 6 volt generators is the field coils, the 12 volt ones for a 64 ford have 3 ohms resistance because they use windings about half the diameter but twice as long as the wire used to wind a six volt generator field coil. I measured the MB generator at 1.5 ohms, so I added into the field circuit a 1.5 ohm ballast resistor. The regulator does not run abnormally hot, nor does the generator field coils. It might not be as efficient as a 12V generator but so far it's doing the job. My friend's son has been driving the MB daily for the last two months, and before that on weekends, It's still charging well and the 12 V battery has not needed a charge.
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Re: 6v to 12v question

Post by Chuck Lutz » Fri May 18, 2018 10:54 am

David.....considering all you have to go through to go to 12-volts, I would ask WHY? I know that winter in Paris is very cold and can be snowed in, but here in the states the gee members cover the deserts, the mountains, the seashore and the fertile plains....meaning aside from some tuning differences, a 6-volt jeeps that has a properly serviced components, that is properly grounded and has a battery with enough cranking amps will perform just fine.

You have almost all the 6-volt components anyway, aside from the battery which normally only lasts for about 5 years +/-, the rest of them will only require cleaning and lubrication for many years unless you do 15,000 KM or so annually anyway.

While it is the purist in me that initially says "WHY 12 VOLTS AGAIN?", it's not like you are starting from scratch with none of the items of either variety. Of course it is up to you but mixing things electrically just does not sound like the best plan to me...
Chuck Lutz

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Re: 6v to 12v question

Post by Wolfman » Sat May 19, 2018 4:31 am

Interesting Marty.
Some time back, I believe one of the members from Australia said they were using a 6 volt gen. to charge a 12 volt battery. Did not remember the details.
I know there is a difference in the field windings and the obvious one being the 12 volt winding is a lighter gauge wire. Mechanically changing the field resistance value.
From what you are saying, just install a resistor, same same as the ceramic resistor used with the 6 volt ign. coil, in the field wire ?
Would think the resistor would need to be able to carry a fair amount of current.
And of course, use the 12 volt regulator.
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Re: 6v to 12v question

Post by Marty, SoCal » Sat May 19, 2018 6:42 am

Yes Wolfman, I used an ignition ballast resistor, 1.5 Ohms. I was worried that the 6V field coils would draw too much current at 12 volts and overheat. Seems to be working fine. Measured voltage at the field coils are around 7.5V running.

With civilian 12V H5006 halogen headlights installed, they are a lot brighter than the originals, even when he was running with 8 volts.

My friend's son's regular truck has been broken the last two months so he has been driving the MB daily to work, about 5 miles each way. Now he has a new truck as of last week so my friend has it back now. He will now drive it daily for a couple weeks as his F-250 is in the body shop. He'll be driving it 16 miles each way to work, I'll update if any problems arise. Note, we are looking for a WW2 Autolite 12V regulator or regulator guts to replace the civilian regulator so it looks more correct.

On the 6V vs. 12V starter differences, if you study the 1949 parts manual, it shows that the differences between the two are the drive has a different spring (I assume heavier on 12V) and the field coils are different, they both use the same armature. The difference in the field coils is on the 6 volt they are wired in parallel, in the 12V they are in series.
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Re: 6v to 12v question

Post by r w devon » Sun May 20, 2018 2:15 am

Marty
All very interesting as I'm likewise aiming to run 12V from a 6V generator through a solid state regulator. My plan was to see how well it would work simply using as is , and if not satisfactory , was going to get the field coils re wound for 12V .
The idea of a ballast resistor sounds tempting .. But as a novice auto electrician I'm not sure precisely what one is, and where physically in the circuit did you put it ?
Thanks

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Re: 6v to 12v question

Post by Wolfman » Sun May 20, 2018 5:33 am

Need to put the ballast resistor in the field wire, between the voltage regulator and the generator. This will increase the overall resistance through gen. field circuit.
Now that you mentioned it, Marty, I do remember another discussion about the 12 volt starter fields being in series instead of being parallel.
Was not aware of the heavier drive on the 12 volt starter but would make sense to use it, especially if running a 6 volt starter on 12 volts.
Update.
Still thinking about the post I mentioned. About converting a 6 volt starter to 12. Or maybe a 12 to 6 ???
Seems this starter had the large stud in the field housing, for the cable connection, on the front ( nose end ) instead of the rear but there was still a hole on the rear ( brush end ).
Question was, Why move the connection forward ?
But I do remember in the process, the field windings were changed from series to parallel.
Probably never find that post again.
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Re: 6v to 12v question

Post by r w devon » Mon May 21, 2018 10:50 am

Thanks Mike ,

I've googled ballast resistors... Thinking where to hide it if needed.

A slight diversion , but still pertinent to 6V / 12V , can you polarise a 6 V generator from a 12V battery ?

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Re: 6v to 12v question

Post by Marty, SoCal » Mon May 21, 2018 11:32 am

Yes, polarizing just orients the magnetic fields in the generator.
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Re: 6v to 12v question

Post by David V » Mon May 21, 2018 12:19 pm

Marty, SoCal wrote:
Fri May 18, 2018 9:59 am
About six months ago I converted a buddy's MB to 12 volts, he was running it on 8 volts and didn't want to go back to six volts. I used the stock 6 volt generator and a 1964 12V Ford civilian voltage regulator. Switched all the bulbs and the coil, too. (The fuel gauge has been dead for a long while, we'll address that soon)

The main difference between the 12 and 6 volt generators is the field coils, the 12 volt ones for a 64 ford have 3 ohms resistance because they use windings about half the diameter but twice as long as the wire used to wind a six volt generator field coil. I measured the MB generator at 1.5 ohms, so I added into the field circuit a 1.5 ohm ballast resistor. The regulator does not run abnormally hot, nor does the generator field coils. It might not be as efficient as a 12V generator but so far it's doing the job. My friend's son has been driving the MB daily for the last two months, and before that on weekends, It's still charging well and the 12 V battery has not needed a charge.
Now this is what I want to hear ! Sounds promising.
Last edited by David V on Mon May 21, 2018 12:30 pm, edited 1 time in total.
44 MB 356111 "Charlotte" since 21/02/06 - Capstan winch
42WLA 70443 "Lily" since 16/1/10


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