6v and 12v Questions

I prefer to leave the electrical systems original on my tractors.  Use the correct cables and keep things clean and they give no trouble.  If you have increased engine compression significantly you may want to go to an 8 volt battery.  But six volts will start almost anything that came with six volts originally.  Just be sure to use the large OO cables to carry the extra amperage needed for six volt and original works fine.

   He wodnt want   to use maple syurp at to days prices $15-$16 a qt  thats not cheep

Here's another post on a similar topic:

With a 6 volt system, maintenance of battery cable connections, mostly at the battery posts is a twice a year ritual. You can get by doing that for 12 volt systems every couple years, but a 6 volt system WILL let you down much sooner. Its probably more of a problem on a tractor that's not run much than in a car that's run every day, but when I was young my dad's cars were all 6 volt and cleaning the battery posts was something we did twice a year. We didn't have the post brush so we used a sturdy pocket knife and scraped until the post was shiny. What came off was hard. Same thing for the inside of the cable connector, we cut hard lead oxide or sulfate away until we got to soft shiny lead. Grease was a good protectant. Many modern plastic cased batteries leak fumes around the posts which is harder on keeping the connections clean. The red and green felts help some there. In the old days with hard rubber battery cases, the posts were actually cast in place leaving no gap around the posts, but the modern plastic cases won't stand that, so there's a gap.

Sturdy battery cables (not from the Wallyworld kiosk) are critical to good starting with 6 volts, as are clean connections at the cable connections to the chassis, and to the starter switch. While some AC run the grounded battery cable to the battery box, it would be better if it was run to a starter mounting bolt.

Gerald J.

I agree 100% with Steve and Gerald. 6V doesn't have much "room for error". I did convert my CA and Oliver 60 to 12V to add a few brighter lights.

If you increase the starting voltage on a series wound starter on DC the amps will increase as will the torque. Its NOT an AC motor where the amps are inversely proportional to the voltage. E.g. on low voltage the AC motor draws more amps because the frequency sets the shaft speed and the shaft speed sets the load. It takes watts input (volts times amps times power factor) to create shaft horsepower. With higher voltage (until you run into saturating the magnetic core on peaks) the current goes down to produce the same horsepower.

But that's not the case with the series wound (as in starters with awound field) starter motor. It starts out stalled and the current is limited by only the circuit resistance, being that of the battery, the cables, the starter switch, and the starter itself including the brushes.  When you raise the voltage you raise the current and when you raise the current you raise the torque so any old starter cranks any engine faster with higher voltage. And when you've bore, stroked, and increased the compression ratio, the old starter may not crank it without increasing the voltage.

The main benefit of 8 volts vs 6 volts is it allows a longer interval for cleaning battery posts. They can get cruddier before it won't crank the stock engine.

12 volts on some magneto engines can make for poor starting because they crank too fast for the impulse mechanism to function, but not fast enough for decent ignition.

As Steve points out, worn out starters, especially bearings and brushes are a problem just because a 6 volt tractor is 50 years old or older.

The winding insulation in a motor is usually tested at rated voltage Plus 500 volts so the insulation isn't different for 6 volt vs 12 or 28 volt. I have run a 6 volt generator as a 12 and 24 volt motor without damage. it makes a fine 24 volt motor. But the field is fully saturated and probably also runs on the hot side which is what will take the generator out. The starter motor with its series field will scream like a banshee at 24 volts if the bendix misses and probably throw the windings out of the slots. I did that to a 12 volt starter on my gas 4020 a few years ago when something in the starter circuit stuck and kept it in gear with the engine running. That rebuild too a new armature as well as solenoid, bearings, brushes, and bendix.

The series motor is a constant torque motor, so its not damage by stalling while cranking, but if its left unloaded and its more than a couple HP, it will spin faster than the winding anchors can hold the armature windings in the slots, then it stops in about 1/8tb turn locking the armature in the field poles. Sometimes it can be rewound.

Gerald J.

ohms law was written on pure dc circuits . the answere is yes  it will start on 24 volts the starter ran cooler on the 24 volts than it did dragging on the 12 volt 1050 cranking amp. Did the test today after posting the question.

ML, did the whole tractor try to roll over on it's side? I remember the Myth Busters trying to verify a myth on CD's shattering inside a fast CD drive. They ended up using a router to do it. When they couldn't get the CD's to explode with the router on 120V, they switched to 240V. Then they didn't last long, neither did the router motor.

If 6 volts aren't worth using in the field, what did he think of magneto's ?

MilesGray (CO/KS) wrote: Jerry used to be a puller so he had changed most of his tractors to 12V, but I will have to ask him about magnetos...

He must have not been a fan of compression on his pullers or he would have had to have more than 12 volts to turn a starter fast enough to crank one