Jumping 6v with 12v:

[40ford]

I know this question has been asked many times,but here goes again.I need to jump a 6v positive ground with a 12v battery.Is it ok to just hook the batteries up normal to get a fast start? Thanks,Russell

[Brendan]

i guess so, i have done it twice. i just made sure that it starts fast.

[Jack E/NJ]

Hmmm. I guess not advisable. 8^)

Jack E/NJ

[scrapiron]

I'd jump the starter with 12, but not through the system.

[Mike51Merc]

Originally Posted by 40ford

I know this question has been asked many times,but here goes again.I need to jump a 6v positive ground with a 12v battery.Is it ok to just hook the batteries up normal to get a fast start? Thanks,Russell

"hook the batteries up normal" as opposed to abnormal?

I've done it. Make sure the lights and other items are turned off.

[V12Bill]

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I've jumped the starter many times as starters don't know the difference between 6v and 12v, they just run faster. Jumping a 6v battery with 12v is not a good idea, but if you must, do it briefly.

[Russ/40]

I hook directly to the 6 volt, neg to neg, pos to pos. I make it a two person operation so the contact is just long enough to start it. Doing that, I have never had a problem with any component failure.

[Gumpy]

I've done it with another person to take the jumper cables off as soon as it starts!

[19Fordy]

I did it many times. Then one day when I did it, the side of the 6V battery blew out- literally. Must have been hydrogen sulfide gas vapor.

[Old Henry]

Originally Posted by Russ/40

I hook directly to the 6 volt, neg to neg, pos to pos. I make it a two person operation so the contact is just long enough to start it. Doing that, I have never had a problem with any component failure.

Ditto.

[FlatheadTed]

On a pre 37 car one cable neg or pos from the 12 volt to the starter terminal on the starter ,Then the other cable from the 12v is touched to start on a head stud or the body of the starter ,On a post 37, One cable to the solenoid on the starter side not the bat side .Then the other wire to earth as on the previous pre 37 .The key needs to be on In both cases the power is kept away from the 6V battery by the starter switch ,This way you are reliying on some charge left in the 6 volt battery to run the coil .you could have a battery charger hooked up to the 6v to boost the 6 volt .

[G.M.]

When the 6 volt battery is so low it won't turn the engine the 12 volt battery when hooked to it is going to be pulled way down in voltage so you won't have 12 volts to the 6 volt car anyway unless the 12 volt jumper source is off a running alternator. I have used 12 volts many times with no problems. When on trips or tours I carry a battery pack. The one I have now also provides 12 volts DC from a cigar lighter plug and 110 volts AC and an air compressor. The nice provision is the cables do not have power until a switch is turned on. You can hook the the POS cable to the block and the NEG cable to the starter cable turn the ignition on then turn the power switch on the battery pack and the starter turns. The 12 volts is only going to the starter and not entering the 6 volt system at all. If the 6 volt battery had enough to just nudge the starter there should be enough voltage to the coil to start the car because the voltage left in the 6 volt battery is not being pulled down by the starter. G.M.

[ford1]

just borrow a 6v batt, or use a charger with a 200 amp engine start feature,

[3340]

what ford1 said,please!

[flathead47]

jumpering 12 volts to a 6 volt battery is not a good idea , worst case the battery will blow up as 19fordy had happen to him. The battery plates/cells within the battery are not designed to have 2x the voltage across them. You may get away with jumpering the battery for a while but each time you do this you are putting stress on the cells , reducing the life of the battery & putting your self at risk. Battery acid on your face or hands is not good.
My 2 cents worth.

[Karl Wolf]

I worked in a gas station and sometimes drove a tow truck when I was young... Never had a problem with jumping 6v with 12v... And there were plenty dead 6volt batteries in the 60's... Hook the cables to the 6v first, just to be careful... Be mindful that hydrogen gas is emited from a battery that's being charged- it makes a wonderful explosive...
Karl

[FlatheadTed]

Understanding this process is a very good tool if you own a flathead on 6 volt . If you follow my post you will have no problems .I have been doing this for 30 years 2 pictures of how to do it ,one 37/39,& 32/36

[Brendan]

Originally Posted by FlatheadTed

Understanding this process is a very good tool if you own a flathead on 6 volt . If you follow my post you will have no problems .I have been doing this for 30 years 2 pictures of how to do it ,one 37/39,& 32/36

that makes sense, you will not heart anything that way

[36Bill]

flatheadted, is that righthand drive?

Bill

[FlatheadTed]

Yes Bill it is ,Just need to make sure the jumper wire is on the starter cable side.