Jump start using 12 volt battery

[JIPJOBXX]

How dangerous is it to jump start a six volt car with a 12 volt battery? Just want to know in case I ever haft to do this.

[Dennis Hemingway]

I use a 12 volt batery to jump the 6 volt battery in my old 9N Ford tractor, with no problem.

Dennis:cool:

[james curl]

You would touch the hot 12 volt wire to the same side of the starter solenoid that goes to the starter or directly to the starter terminal after grounding the 12 volt battery to the frame or engine of your car and turning the key on. By doing it this way no voltage will flow through your 6 volt solenoid or coil. The key must be on for the engine to start. You remove the hot 12 volt wire as soon as the engine starts. Do not under any circumstances let anyone mash the starter button while the 12 volt wire is contacting the solenoid or the starter terminal as that would cause you to send 12 volts to your 6 volt starter solenoid and coil plus back feed to your generator and voltage regulator.

[JIPJOBXX]

I guess I must explain I have a foot pedal activated starter and no push button to use. How can I do this with this system?

[james curl]

Does your foot pedal starter contact a mechinical solenoid mounted on top of the starter? The pedal should push a bar that pushes on the center button of the mechinical solenoid. There are probably 3 teriminals on the starter solenoid, one with a cable to the battery and one with a strap or cable into the starter, these will both be about 3/8" diameter studs. If you have a third terminal it will be a number 12 wire to the coil. You touch the 12 volt hot wire to the side that goes into the starter. When you step on the starter pedal it pushes a copper bar across both the wire from the battery and the wire into the starter which causes the current to flow into the starter and start the engine. If you just ground a 12 volt battery to your car and then touch the 12 volt hot wire to the terminal that goes into the starter it will cause the starter to run, starting the vehical.

[JIPJOBXX]

What I'm reading is to place the positive side of 12 volt battery connection to the hot lead side of the starter motor. But one question, I understand that but you said the positive lead of the 12 volt battery, shouldn't that be the negative side of the 12 volt battery as our cars work on positive ground.

[james curl]

The battery that you are using does not care if the car is postive ground. The starter will run with either ground. All you want to do is make the starter run with an outside source of power. This should be an independent action much like running the starter on the bench, it will run with either the negetive as ground or postive as ground. With the starter on the bench and grounded through the battery only one terminal on the starter will make the starter run, this is the only terminal that you can touch with the other wire from the battery and have the starter run without any other action from you.

[jamesadams]

Be careful. When i was a teenager, i was helping a fellow start a 39 plymouth he was fixing up. He boosted it off of his 12 volt pickup and the battery exploded. He is, and was at the time quite knoledgable around such stuff. The best i remember he was boosting straight to the battery, though.

[Merle Coggins]

If your starter is like the one in my truck (mechanicaly activated by foot) then there is only 1 cable connection and I would advise not to use James' method, since there's no "after the solenoid" connection.

It sounds like a good method if you have a starter solenoid, but I would still keep the polarity the same just to play it safe.

That said, I've jump started many 12 volt machines using a 24 volt jumper pack. I connect the Hot lead to the battery or starter post. Then I try to have an assistant crank the engine. Once the assistant turns the key to the start position, I touch the gound lead (away from the battery because it'll spark). You get a surge of voltage, engine spins rapidly and usually fires right up. As soon as it fires, remove the gound lead. This method has worked sucessfully for me on many occasions. It gives a momentary shot of higher voltage for the starter, but usually the rest of the system isn't effected.

And again I'd advise to keep the polarity the same and don't let the vehicles touch.

Merle

[1just4don]

My only additional advice is make double sure,,,no make that a triple check,,,and have the car or pickup,whatever in neutral. Otherwise it can run over things,,,including YOU,,,real quick. many an accident has such occured. These cars dont have neutral safety switches. Tractors are noted for this,,,working on them from the ground.(and some by-pass the neutral switch,,,like "ME") Had a REAL close call one time,furtherest thing from your mind while you are working on a troublesome vehichle of ANY kind!!! Sorta hate to hear of any scratched up pretty fenders here from something so simple. Hard to replace grandkids too!!!

[Young Ed]

I'll second that warning. My old truck has a foot starter so I often have one foot on gas and one on starter pedal. One time forgot to put in N and it started in gear and putted right out of the garage. Thank god the door was already open! That was when I first got it and still lived with my parents. They wouldn't have been pleased if I smashed through the garage door!!!!!

[grey beard]

Y'all will do well to follow the Merle's advice here. Batteries only ever explode for one reason - hydrogen gas builds up around the vent areas of a battery any time it is either charged or discharged in a very rapid fashion. This means that if you have just finished cranking her till she won't turn over any more, and now you come at her with jumpers, there will be hydrogen gas around the parent battery. This is why Merle suggests you do your connecting and disconnecting with the GROUND jumper AWAY from the battery.

The other thing you don't want to do when jumping six volt systems with twelve volts is to hook up the jumper and leave the key on - even one minute more than necessary. This scenario has the ability to cook both ignition points - if they are in the closed position - and coils. That having een said, your six volt starter can run long and happy on twelve volts. It is only the ignition and charging systems that may become unhappy at having to face this double electrical pressure.

I still run a stock ignition and charging system of six volt variety. It costs like the very devil to rebuild and replace six volt generators and regulators. For this reason, in the few instances where I may jump the six volt system with twelve volts, I take a minute to disconnect the BAT terminal wire from the voltage regulator - only takes a minute and protects the system.

On the subject of jump starting, the very idea of this act is an admission that your starting/charging circuits are not all they should be, else you would not be reduced to jump starting. A good group II six volt battery that is kept fully charged will crank an engne for an amazingly long time before it begins to fail, IF the terminals are all kept clean. If you live in Anartica or Iceland and a group II is insufficient, consider two Omni six volt batteries in parallel. This still charges with your six volt system, but will let you crank your engine till the radiator boils over, AND you can tap off of the opposite ends of the two six volt batteries and get twelve volts for your CB and Tunez - Why, you could even make the twelve volts you get this way either positive or negative ground without respecrt to the rest of the vehicle - sorta like having your case and eating it too . . . . . .

[JIPJOBXX]

Well that all useful information and remember this is only in a case of emergency! Maybe I could find an old hand crank to run through the front and yank on it a few times. No only kidding I did that when I was a kid on my Model A's but with this old body I can hardly pick up a beer!

Just one more question could I install a lead wire on the starter solenoid and leave it somewhere down by the steering column just in case this scenario ever happened.

[JIPJOBXX]

Ok the final conculsion is that you can quick start a six volt car but do not leave the key on for any reason except when turning over the engine. Can you just take the leads oft the 6 volt and attach the 12 volt battery cables to that point??? Jon

Just trying to get this strait (nice and simple) that me.

[1just4don]

My feeble brain says no to turning over the starter with the key, MY idea of proper jump with 12 to 6 IS key on,,,gear shift in neutral,are you sure its neutral,check again,,,okay remeber best to check thrice,check again. Head under hood hook hot lead to starter"ONLY" terminal on the starter.(directly) then stand with head back a bit and touch ground to something solid,,,as said will get some spark,,,stay away from battery with it. spin till start(should be quick)(unless 30 below or bad parts).

Basicly I did the same thing on a daily driver in the early 70's,,,had a 12 sitting on the hump,inside, and had a cable direct to starter and another direct to ground. Left one on and only held other close enogh to make her spin. I was working at a place where I "HAD" to be there at a certain time(very early) like 5 AM EVERY morning 6 days a week for ten hour shifts(that got real old real fast)(in a packing plant no less)(defined-hard work-poor environment). Looking back I am lucky I didnt blow the inside one in my face with it sparking direct all those times. Did have one blow in my face years later with different circumstances,,,not something you ever forget,,,and I mean not a graze,,,a "SMASH" in the face with the whole battery top. Thought I was going to lose my sight for a 'few' minutes or longer. Scary,, real scary,,,but my fault for dropping a wrench that hit both posts at once. Another safety tip,,,have a cover of most anything,wood,cloth, heavy plastic,cardboard,anything to lay over the top of a battery while you are working on ANY car to prevent doing exactly the same thing. Some lessons in life are earned harder than most!!!