Is it possible

to jump start a 6 volt positive ground tractor off a 12 volt negative ground vehicle? Don't have need to do that now but, I am purchasing a cub with 6 volt positive ground electrical system and I just thought "what if" I had a dead battery down the road? Never had positive ground system before.

I do it.

It doesn't make any difference if it is positive or negative ground. Simply jump positive to positive and negative to negative. The problem is why did the battery need help. Need to repair what went wrong. Al71

well, I have done it. Not the optimal situation. I don't recommend it, but in a pinch, a number of us have jumped a 6v system with 12 volts.

The positive vs. negative ground is just reversed polarity. so, the positive leg (terminal) is connected to the frame. As long as positive goes to positive, and negative goes to negative, that is all that matters.

There are horror stories around using 12v to jump a 6v system. I personally have never experienced it, but others will share their comments. After getting the polarity correct (red to red, + to +, etc), the main thing is, the only thing you should do is start it. do NOT turn on the lights, etc. I do NOT hook the jumpers up to the battery. I hook the positive to the frame, and then use the negative cable on the starter post. This is best if you have a magneto (which I prefer). Battery ignition will fail after you remove the jumpers if the battery is totally dead, and the charging system is not working properly.

The best route is to invest in a good 6v charger, one with a starting cycle setting on it.

[b:40300f6706]disclaimer: [/b:40300f6706] my comments are to be used at your own risk. I have been working on mechanical things for almost 50 years now. there are things I do in a pinch that are not for first timers or the faint of heart.

Positive to positive you should be good. If it was me when and if, and there will always be an "if" that happens, I would then convert to 12 volt. Can be done easily for around 100 dollars. 50 dollars for 1 wire alternator, 20 dollars for internally resisted coil, then 30 or so for cheap 12 volt battery.

Rule #1: Ignore "ground." Positive to positive. Negative to Negative. PERIOD!

You will get mixed reactions about jumping a 6V battery off a 12V vehicle.

Some people will tell you that it is an absolute death sentence. The battery will explode in your face and turn you into a hideous acid-burned monster.

Yes, the battery can explode, but the battery can explode in a standard jump start too!

All I can tell you is that I've jump started 6V tractors off 12V vehicles many times, with no problems. Positive to positive, negative to negative.

I make the connections at the starter, not at the battery.

I also don't waste any time. Hook up, get the tractor started, and unhook.

As was said,positrive to positive.Negative to negative!However,I 'ground' (+) to the frame and hook to the starter(-) to avoid the battery.

(quoted from post at 08:53:30 02/16/15) Positive to positive you should be good. If it was me when and if, and there will always be an "if" that happens, I would then convert to 12 volt. Can be done easily for around 100 dollars. 50 dollars for 1 wire alternator, 20 dollars for internally resisted coil, then 30 or so for cheap 12 volt battery.

Click to expand...

If it were me changing to a 12v system, I'd also change the field windings of the starter to 12v. I was having problems with my 240U until my "auto-electric guy" said the starter was spinning too fast before engaging the starter ring and that was the reason for the wear on the ring and starter drive gear. also noticed before that it often started just as I let off the button and not while cranking... 12v windings fixed that too... about another $100 to change out the windings, but it never started better.

You need to unhook the wires on the starter use a small jumper from the batt cable to the other kea so you have batt power to the coil. Then you can hook 12v to the starter. That way you will not be feding 12v into the system gen,reg and coil. Your gen and reg wont like 12v

protect your eyes batts can explode easy its just not worth the risk.

I do it all the time but don't even think about hooking to the battery. hook negative to the starter not the solenoid, turn key to on not start, then hook positive to ground, it should turn over and fire, unhook immediately. do not crank for more than 5-10 seconds at a time.

Buy a crank and make sure the timing is set by the book. A Cub is easy to crank start. A battery that won't turn the engine over will still usually fire the ignition system. If the battery isn't strong enough to do that, the engine will die as soon as you unhook the jumper cables anyway.

I agree with Jim.
The wiring burned up on my Cub years ago(long story), it starts so easy with the crank, I've never bothered to fix it.
Mine has a magneto, so no need for a battery.

Ben

This battery came from a tractor with a bad regulator(alt) so that it was overcharging at about 16 volts. It must have boiled most of the water out and got hot one day and spontaneously exploded, and I do mean exploded.
Years ago while jumping a 6v from a 12v, I made a spark when my sleeve hooked one of the jumpers on the 6v battery, Ka-Boom, piece of the case hit me in the chest, ouch, acid all over! Taught me a lesson. Be careful as Gene says...

Guys, be careful what you tell someone to do. The cub has the switch on the starter. If you hook your jumper cables to that terminal you are also hooking to the battery. This is dangerous like been explained. A cable would need to be disconnected to be safe and then you have to hook appropriately to ignition or it still won't start. On starters like on an older H or M that have the starter switch separate from the starter, then it is perfectly safe and acceptable to hook a 12 volt boost on to the starter by NOT touching the starter switch. Other models and conversions have a magnetic switch on starter or remotely mounted. They also can safely be jumped by hooking to starter side of magnetic switch(commonly called solenoid) Some one who is not up on electrical components can get into a whole lot of trouble. I have seen it all the time over the years. Even after showing them, telling them, explaining it to them, they hook up wrong. Blown up batteries are no joke. Sure you can blow one when doing everything right, but the odds are way, way, down compared to exposing a 6 volt battery to 12 plus volts.

i always use a extra battery,not in anything, so i don't cross anything wrong, then pos to pos, neg to neg....

Guys, what everyone needs to remember is, hydrogen is produced when you charge a battery. it is the hydrogen that is dangerous and explosive. When you put 12v to a 6v battery, the hydrogen production is almost doubled in a short time, not giving it time to dissipate. it is not so much the short application of 12v, it is the amount of hydrogen produced. now, create a spark, no matter how small when you remove a jumper cable or just spark from an arcing armature. Same thing can happen when charging a battery on "quick charge" even at the correct voltage.

Boom! can you say Hindenburg?

Guess I opened a can of worms here. Thank you to all who responded.

Not a can of worms, but actually some good information. We can be a crusty ol' bunch. There was good info in this whole posting.

May I add a little to your post? The charger maintainer that has been covered on here from WalMart. Has automatic 6/12 volt select and it does everything all by itself! Only like $30.oo. I bought one about three months ago and LOVE it!!