Farmall C 12 volt battery size. which one fits the box?

On a whim (because my 6 volt battery was dead and I happened to have a brand new 12 volt battery and a good 12 volt coil laying around) I switch my C over to a 12 volt system yesterday. The battery I have came out of a Ford Taurus, I think. I could have been out of an escort ZX2. Anyhow, it didn't fit inside the battery box, so I took the box off. Now, it doesn't fit in between the tank and dash, unless I turn it sideways.

So, I was wondering if anyone had an Advance Auto Parts, or Napa number for a smaller sized battery that most closely resembles the 6 volt battery that I had in there.

Also, while I Am thinking of it...

My battery box had the bottom rusted out of it, and someone welded a piece of steel in there before I bought it. Originally, did the bottom of the box have some special feature(like indentations) to accomodate some nuts welded into the bottom? When I got it, it had bolts with nuts so that the box could not be removed without removing the battery, which meant that I had to take the gas tank off, to remove the battery. That is a pain in the butt!

Looking back, I guess it would have been easier to tow the tractor up to the garage and plug in the charger, rather than remove the gas tank in the 10 degree weather.

If your going to 12 volt a group 24 will work . As for myself i would have used the stock coil and installed a ballast resistor .

Group 24 will not work, too big. Group 26 or 26R ( NAPA 5026 or 5026R) depending on your preference for post location.

I should have said a 22 not a 24 some days my finges don't do what i want them to do as to the 26's now that is a new one on me , But i am old school all these new #'s throw me . I know the 22-24 -24f27-27f -31- a D8's. and the 6 volts . So bet me this time.

I am old school too. Group 22 is what I used to use until we couldn't find them around here.

Thanks for the info.

It's getting harder and harder to order non-auto parts from places. All these kids know how to do is ask you what year/make/model, and if the computer doesn't know it, they say they don't have it.


You mention a group number to someone, and they are just lost.

I used to build things from scratch all the time. I would just go in, ask to see the parts book, and find something that had the specs I needed and order it. Now, unless you can find the vehicle that the part goes to, and order it that way, you aren't getting it!

...not to mention that the price of steel stock is so high that it is cheaper to just buy something chinese that is already built, than try to build it from steel stock... Oh how I loathe this.

John_PA: One of my pet peeves as well. There used to be fifteen plus linear feet of paper in a good parts store and a good counterman could find almost anything. Now my local parts place retired the two old guys I could count on and the kiddie replacements can't do anything without the application. There are a few lonely books off to one side--mainly special custom made stuff. I have to teach the kids where to find things. Last time I was in, kid asked ME for help with a customer who needed a tractor part.

John: Actually quite a simple task, measure the box and go to NAPA. Why anyone would switch a C to 12 volt is beyond me. Tune up the tractor ignition system, charging system and cables, and 6 volt will start a C anywhere in North America, that you can stand to be out in the cold for 10 minutes. Good for minus 40.

I once started a 6 volt Farmall 300, unassisted by anything other than the tractor's own battery at -40F.

I have a 6 volt SA, 12 volt 130 and 12 volt 140, all have alternators. Been 18-19 years since I did the SA and 130. 5 years on 140. At -20C roughly -2F my Super A will fire up just as fast as the other two. Super A has been a lot less trouble, first 6 volt battery lasted 13 years. Never got much more than half that out of a battery before. I give the credit to excellent charging. 18 years later the SA has had one new battery, and that is total electrical repair other than plugs, points and condenser.

Farmall 130, 12 volt alternator at same time as I wanted to operate a 12 volt motor. 18 years later it's on 4th battery, 2 nd alternator and $217. rebuilt starter, caused from spinning too fast and centrifical force dislodged the armature whindings.

Plain and simple these little engines spin too easy if compression is off 30 psi from new. Low compression engines don't fire up quite as quick, spin faster and longer, therein lies the death of a 6 volt starter. Sure you can go 12 volt in H-M and larger, those engines cause enough more resistance to load the starter.

Let me assure you, next time I need batteries for 130 and 140, they will become 6 alternator tractors. I no longer have the 12 volt motor.

Hugh,
I rebuilt (and modified slightly) my engine. Well, no... I take that back. I have a 1953 Super C engine that I rebuilt and modified and put into the C. It's got about 140 psi of compression in all cylinders and has new rod and crank bearings. I have less than 2 hours of run time on it since I did the switch. At the absolute best, with a very fresh fully charged battery, I would get 2 revolutions of cranking that were pretty slow. I rebuilt the starter, thinking that maybe if it was fresh, I would be ok. Nope... still too much for the 6 volt system.

So, like I said, on a whim, I converted it to 12 volt, and since the 6 volt charging system was not working anyway, I just left all that disconnected for now.
My farmall cub, which has about 80 PSI of compression and a magneto is still on a 6 volt system, and I am leaving it that way. It does just fine. But, unless I managed to loose about 40 lbs of compression, I am leaving the C just like it is. (If for any other reason, it is too cold to be out there changing parts around. If I didn't have to empty a load of manure, I wouldn't have been starting it yesterday in the 10 degree weather! haha)


Just curious, did you ever try an 8 volt battery on a 6 volt system?

John: You'll be okay. I got along fine until this 130 got a little long in the tooth. I've always said, big secret to 12 volt was keep tractor tuned up well enough so it fires up about 2nd revolution. Even without the speed factor, the tractor that fires up in 15 seconds, has 4 times less starter use than the tractor that takes 60 seconds to fire up.

I wouldn't pay any attention to the guy who suggested going with 6 volt coil and a resistor. I bought new 12 volt coils from CaseIH, one for 130, one for 140, after I got to a quart of burned out resistors. What a damn waste of time those resistors were.

Hey i suppose you guys dont have a canadian tire store there. Thats where i got my last battery and it fit perfectly. I paid 75 dollars for it.