CA 6 volt or 12

I recently purchased  a CA. I need a new battery. It has an 8 volt in it now. I was told 

It was made 6 volts. The 8 volt battery allows lax maintenance of battery connections. If there are lights they don't last as long on 8 volts. These days 8 volt batteries are not very common and the selection of 6 volt batteries are limited. Batteries sitting on the store shelf for months or years are bad purchases. The motor vehicle world along with tractors changed to 12 volts about half a century ago.

The original 3 brush generator has no voltage regulation, just some current limiting adjusted by the light switch also connected to the field circuit. Until the operator turns down the current sometime with the light switch, then 3 brush generator is guaranteed to overcharge the 6 or 8 volt battery leading to loss of electrolyte from being converted to a combustible mixture of hydrogen and oxygen in the optimum ratio for the beast bang if ignited. The most reliable way to tell the battery is being overcharged is detecting bubbling of the electrolyte. Don't use a match to provide light to see the electrolyte, the battery acid will eat your clothes and your skin when the battery explodes. Battery pieces will hurt where they hit.

The next generation of generators with a voltage regulator was a giant step forward in battery life maintenance.

Speaking of maintenance, the battery posts in a 6 volt system need to be cleaned twice a year whether used or not, there isn't enough voltage to tolerate slightly corroded connections. There is more tolerance with the 8 volt battery. !2 volt systems can run a couple years between battery post cleaning sessions.

To go to 12 volts for the best function, a small alternator with a built in solid state regulator will give the best battery life, but its obviously not original. For battery care its a new world. A generator can be found to fit wound for 12 volts or the 6 volt generator can be turned faster (needs to about double in speed to double the voltage) and connected to a regulator for a more original look.

Then for 12 volts any lamps will have to be changed, if there is an ammeter it will need to be 50 amps full scale for the alternator instead of the original 20 or 30 amps. The ignition coil (unless its a magneto) needs either a ballast resistor with the same resistance as the coil primary resistance or a new 12 volt rated coil. Some vendors on this forum do not trust the ballast resistors. My gas 4020 uses a 6 volt coil and originally used resistance wire to drop the voltage, but when I bought it ten or fifteen years ago, it had a ceramic ballast resistor that has worked more reliably than the wiring cobbles connecting it with a ScotchTap that went bad. It uses the 6 volt coil and resistor so that a special terminal on the starter solenoid applies battery voltage directly to the coil for better ignition when starting pulls down the battery voltage, which is worse with the skinny JD battery than most modern car batteries.

Going from 6 volt battery will also be likely changing polarity from positive ground to negative ground and probably need new battery cables because while a generator can work with either polarity, the vast majority of alternators are only made negative ground because that is the SAE standard since about 1963 and transistor radios are absolutely intolerant of reversed voltage. That also requires changing the primary polarity on the ignition coil and swapping the connections on the ammeter if present.

Not a trivial conversion, but not impossibly difficult, very detectable by the "correct police" at shows. Starting will be better (no need to change the starter), and battery life will be a lot better and the electrical system will need less maintenance like cleaning battery posts and connectors and adding water to the battery.

Gerald J.

GregLawlerMinn wrote: Gerald hit all the highlites. My preference is to convert to 12V(+grd) due to availability of decent batteries and components. I have used the short 12V genneys from old Chevys and mounted the VR in the tool box to somewhat disguise the upgrade. If you intend to keep the tractor working; you may also want to consider upgrading it with the Petronix Electronic Ignition module and coil.

Go with negative ground if you switch to 12 volts. Sometimes you can special order positive ground 12 volt components and alternators, but positive ground is no longer the 12 volt standard.


Edited by DougS - 12 Aug 2016 at 12:38pm

I have converted all my tractors to 12 volt neg ground. I also converted dads tractors. 6 volt will start them it's what the factory put on, If originality is most important to you. My tractors might sit for 6 months before I need it and I don't like to be fiddling around to get it going when I need it. I just put the batteries I take out of my diesel after five years and put in the tractors they'll usually go another five years before I touch them again.

I'm a purist and prefer the six volt system.  If you use the proper size cables, six volt needs a large cable to carry the amperage required to turn the tractor,  Size #1 minimum, six volts will turn your CA like a top, and be original.  I use six volts on everything that came as six volt, boosted compression WD45 included.  But that's just me.