Farmall M 12v or 6v

Eboor1995

Member
Hi I just bought a 1950 Farmall M and it has an old 12v truck battery that needs replaced. I’m not sure if it’s been converted to 12v or if it’s 6v. How do I tell? The tag on the starter is beat up so I can’t read it. Thanks
 
Runthe 12V. The starter wont care. The chargeing system is most likely toast. Now would be a good time to convert to single wire alternator.
 
Hi I just bought a 1950 Farmall M and it has an old 12v truck battery that needs replaced. I’m not sure if it’s been converted to 12v or if it’s 6v. How do I tell? The tag on the starter is beat up so I can’t read it. Thanks
Very hard to say if 6 or 12 V. Most conversions are done with alternator. If you still have a generator chances are it is still 6 V. Not uncommon for someone to put 12 V battery in a 6 V tractor and run it that way. Probably won't charge correctly but if the tractor has a mag battery is only used for starting and will last a while. Chances are no one will have changed starter even if converted to 12 volt. If it has generator you could get numbers from that in case someone converted it to 12 volt generator. If it has a distributor check to see if there is a resister ahead of the coil.
 
Nearly all 12V conversions use the original 6V starter.

Look under the hood on the right side at the front. If there is an automotive alternator hanging there, it is fully converted to 12V. On a seldom-used tractor, the owner may just throw a 12V battery on it, and charge the battery when needed, rather than mess with the tractor's electrical system. All it's needed for is to start the tractor, if it has a magneto.
 
Nearly all 12V conversions use the original 6V starter.

Look under the hood on the right side at the front. If there is an automotive alternator hanging there, it is fully converted to 12V. On a seldom-used tractor, the owner may just throw a 12V battery on it, and charge the battery when needed, rather than mess with the tractor's electrical system. All it's needed for is to start the tractor, if it has a magneto.
I just looked it does have an alternator.
 
What size 12v battery fits & works the best on the M? I don’t have the original battery box just plan to put under gas tank and use tarp strap.
 
What size 12v battery fits & works the best on the M? I don’t have the original battery box just plan to put under gas tank and use tarp strap.
Being that is once was 6 volt start a lawn mower battery will start if but the bigger the better and if your going to run it this time of year the highest CCA you can find that fits
 
What size 12v battery fits & works the best on the M? I don’t have the original battery box just plan to put under gas tank and use tarp strap.
I think I would something a little stronger and more ridged than a tarp strap! Maybe get someone to weld up a steel box that fits the location.

I was lucky with my BN because when I needed a new battery box I had a brother-in-law who worked in a shop that built cabbage harvesters and he took the old rusted Farmall battery box and built a new one out of stainless steel cover and all! That was probably about 35 to 40 years ago and it still looks like new today!
 
If I was you I would look for a used battery box from a salvage yard. there are lots of them out there. That tarp strap is not very secure and about the first time you hit a bump out goes the battery breaking it, or shorts out and then a fire burns up the tractor. The best thing is to put the battery in and secure it is a box.
 
Just put a Group 31 with stud top in it and never have to bother with over tightened clamps and cleaning battery connections. Best deal going. We have pretty much changed everything over to them since they are simple connections just an eyelet on the end of the cable. If the starter slams into the flywheel to fast reduce cable size to slow it down slightly and reduce gear damage. I think we have a 4ga wire on our H for that. Works fine even in the winter.
 
What size 12v battery fits & works the best on the M? I don’t have the original battery box just plan to put under gas tank and use tarp strap.
Pretty much any automotive 12V battery is plenty. You do not need a Group 31 unless you plan on jump-starting class 8 trucks with this tractor.

You're not going to find a used battery box at a salvage yard. The battery boxes for these tractors usually rusted away, and the rare good original is the first thing to disappear off a salvage tractor. You're wasting your time even looking.

I don't like battery boxes because they don't allow for ventilation. When the battery inevitably off-gasses it's contained in the box, and causes rot and corrosion which you don't see because it's in that pretty battery box. Then the tractor won't start and you're scratching your head why. Sure you could pull the battery and clean/paint every few months, but who has time to do that? Secure the battery however you feel comfortable securing it.
 
I have three Farmall M tractors for farm use. All three have been converted to 12 volt, negative ground, alternator and electronic ignition. Why? Because they all start instantly. I paid a guy to do the first one and copied his work on the other two. If you DEPEND on your tractors it is the only way to go. Ellis
 
Here is battery hold down scheme, Battery slides out the side.
You can see how the vertical portion s removed so battery can be slid to the left and out.
 

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I have a 1955 300 with 6 volt original system and it spins over just as fast as a 12 volt tractor. It is all in having the right battery, clean good connections, right size battery cables and a starter in excellent condition. My tractor will spin over and start in less than 2 revolutions even on a cold day.
I'm not against 12 volt systems, but with everything correct a 6 volt will do the same thing as the 12 volt.
 
I have a 1955 300 with 6 volt original system and it spins over just as fast as a 12 volt tractor. It is all in having the right battery, clean good connections, right size battery cables and a starter in excellent condition. My tractor will spin over and start in less than 2 revolutions even on a cold day.
I'm not against 12 volt systems, but with everything correct a 6 volt will do the same thing as the 12 volt.
Yes, "with everything correct." It's a constant fight to keep everything correct. 12V requires far less maintenance, and complete conversions can be done for less than the cost of replacing the 6V generator.
 
What size 12v battery fits & works the best on the M? I don’t have the original battery box just plan to put under gas tank and use tarp strap.
A group 24 works well on my 'fleet' of Ms. I built a simple tray to hold the battery.Held down with a simple tarp strap,I have never had a battery come loose.
 

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