6V boost from 12
- Thread starter clark51
- Start date
It would help if you told us exactly what the two vehicles are that you are working with. Connecting a 12 volt battery directly to a 6 volt battery will cause a large spark and current flow at the last terminal being connected. You could blow up one or both batteries. It will also connect 12 volts to any 6 volt components in the car being jumped which is not good especially if there are any electronics involved. It is best to only power the 6 volt starter motor directly with the 12 volt battery so that nothing else in the jumped car is getting 12 volts. More info please on what you are doing. Regards, Kevin.
V8COOPMAN
Well-known member
I can completely agree with turning-off all lights and accessories....makes perfect sense! But...........WHY the necessity to keep the two vehicles separated? Are you inferring that you can't have a common GROUND between a 6v system AND a 12v system?
You ever think about this back in the 1950s? You have a brand new '55 Chevy....12v NEG GROUND. The pretty, young neighbor gal has a clapped-out '51 Ford....6v POS GROUND. It's 4:30 AM, 18ºF outside, and she has to be at the hospital as a nurse by 5 AM. The Ford won't start. She knocks on your door and asks if you can give her a push. You've been diggin' her chili from afar and would love to take her to dinner. You eagerly agree to push her Ford with your '55 Chevy. You line-up behind her with your bright lights on in the dark hour. Bumpers mesh perfectly. You give it the gas. She has the key turned-on. As she lets the clutch out in 2nd gear, the Ford perks to life. She turns her lights on and heads to work. You score BIGLY next Saturday night.
The point is, you had two completely functioning electrical circuits (a 6v POS GND, & a 12v NEG GND), fully sharing a common ground with the two bumpers mashed together. Even though you have a common GROUND, you still have two separate electrical circuits because of the way the two batteries are electrically isolated within their respective circuits. If you connected the two "HOT" posts on the two batteries together, then there would be sparks!
>(IF you connect a 6v battery to a 12v battery in PARALLEL, is the measured voltage 9 volts?)<
I believe you would have a hard time convincing me to 'JUMP' a 6v POS GND battery with a 12v NEG GND battery. I WOULD NOT have a problem jumping my 12v NEG straight through your 6v POS starter DIRECTLY. 12v POS to your starter connection, and my 12v NEG cable to your engine block. With your IGN Switch ON, there should be enough voltage left to fire your ignition. Would not matter if the two vehicles touched. It also would not matter if any of your lights were on, because I'd only be passing current THROUGH the starter. DD
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51 MERC-CT
Well-known member
On the few times I have jumped a 6 volt system using a 12 volt battery, with ign. on, out of gear, connect one 12 volt cable to the starter side of the solenoid (pos. or neg. makes no difference, starter is not polarity sensitive)
Touch other 12 volt cable to battery ground to activate starter.
Touch other 12 volt cable to battery ground to activate starter.
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FortyNiner
Well-known member
While a different procedure, I've used a portable 12 volt battery pack to start a 6 volt vehicle many times. As has been mentioned, no lights or accessories on, connect the pack to the battery, turn on the pack, spin the starter, turn off the pack and disconnect after it fires. Works as a solo act.
I think he means don't let the bumpers touch when jumping battery to battery with different polarity. It would definitely cause big sparks.
Bill
V8COOPMAN
Well-known member
Have you thought-out what you're saying? Think about THIS.....in the case of jumping "Battery to Battery" with "Different Polarity". When jumping as above, you have battery cables attached to POS and GND battery points. UNDERSTAND that the GND cable is attached (electrically) to the same point as the bumper....electrically!
The dead battery that you are attempting to jump (in the dead vehicle) is also grounded (electrically) to the same GND that it's bumper is bolted to. By placing the GND jumper cable on a battery GND (or ANY grounded surface) on the dead vehicle, you're doing the same thing as TOUCHING the two vehicle bumpers! Please explain WHY the danger of touching bumpers.
The real danger is this: Explain exactly how YOU would hook-up POS & NEG jumper cables to POS GND Ford battery....SAFELY!
Anteek29
Well-known member
RalphG
Well-known member
As stated by others, connect direct to the solenoid (starter side) on the six volt system when boosting with a 12. I've done it with the Merc back when I was bringing it back to life. Worked great. No worries of putting 12 volts through the rest of the 6 volt system. Just the starter gets it and you won't hurt that with 12 volts.
If the bumpers touch both car frames become one frame, the 6 volt is positive ground and the 12 volt is negative ground and you've grounded them to the same frame. So in reality you've hooked a positive post to a negative post. Remember when jumping " Positive to Positive and Negative to negative " . You can't do that when the bumpers are touching on two cars with different polarity. If the polarity was the same it wouldn't matter if the bumpers touched
To jump with a 12 volt negative ground car hook up the negative cable to the to the hot/negative cable on the starter solenoid/switch then then hook the positive cable to the frame so if you do cause a spark it's away from the battery.
If you allow the bumpers to touch You're going negative to positive through the frames.
Probably the safest way is to jump the starter only but most people don't do that.
Bill
That's how I have been doing it for years. The starter spins when
the battery pack switch is turned on. G.M.
David J
Well-known member
Plenty answers here but here's my way .
Talking 33-34 stock cars only .
Put the neg on a head nut and the pos on the starter stud .
If you do not touch the starter button you will not back feed the 6v system .
Have the ignition switch on when you touch the 12v pos to the starter terminal and you can run the gas - choke with your other hand .
Talking 33-34 stock cars only .
Put the neg on a head nut and the pos on the starter stud .
If you do not touch the starter button you will not back feed the 6v system .
Have the ignition switch on when you touch the 12v pos to the starter terminal and you can run the gas - choke with your other hand .
V8COOPMAN
Well-known member
Technically, I guess that constitutes "JUMPING" a battery, but that process with the battery pack has nothing to do with a NEG GROUND vehicle jumping a dead BATTERY in a POS GROUND vehicle, especially when it comes to the possibility of "co-mingled bumpers". DD