Is it ok to jump start my 6 volt 1954 F100 with a 12 volt battery? Would I need to disconnect anything first?

 

I've been told many times, having asked the same question, that if you keep the duration its connected to a minimum, and ALL accesories are turned off, it is supposed to be an acceptable procedure. still, it makes me nervous. Whats about 6v bulbs in things like gauges? stuff like that. I have always wanted to build a set of jumper cables with some sort of voltage reducer built in, but people keep telling me not to bother. I'd get more than my opinion here before you do it!

Other opinions?

 

The biggest thing is making sure the polarity is correct on the jumpers (+ to +, etc), and that the bumpers aren't touching. Keep the lights and accessories off, and have at it! People do it all the time with no apparent ill effects, but you do want to minimize the duration.

 

did it all the time,just for short period to turn it over, never had a problem,

 

I do it quite often. My flat six in my '49 F-2 doesn't like to start when it gets below 40, once I kick it over with a jump from my daily driver it's good to go and will start the rest of the day on 6 Volts. My compression isn't the greatess but jumping once in a while with 12 Volts is a lot cheaper than a rebuild for this small problem.

I used 12 Volts to jump the two flat heads 8s I have after they were sitting for a long, long time. The spin you get from a 12 Volt jump compensates for the compression loss from the rings contracting while sitting. After the engine spins a while the rings spread out and seal better. At least that's how it was explained to me and it makes sense. It seems to work. I wouldn't do it for long, just until it pops over, unless you have a heavy drop resistor between the battery and the coil or you're going to fry something. You also have to protect the rest of the electrical system with resistors or keep everything turned off.

 

Friend of mine has a 34 Flatmotor Roadster, all 6V, he has a 12V battery wired in for starting when it gets hot.
He's driven it this way for over 100,000 miles.

 

Same here: have had my '54 since 1977 and have jumped it many, many times with a 6 volt car or truck and have used it to jump start my (or others) 12 volt vehicles. I do try to get the cables off ASAP, off of my truck first and then the other car/truck.

abe

 

Thanks for the responses. My 239 is kind of tired too, so I am going to give it a jolt of 12 volts. It going to work like a defibrilator. When I am about to do it, I yell "Clear"! I hope it don't flat-line!

 

Ok, I didn't yell clear, but I should have.
I was kind of scared about destroying my new 6 volt battery, so I disconnected the negative cable from the battery and connected it to the jumper cable. Then I hooked up the positive jumper cable to the positve battery cable which was still connected to the battery. Then I connected the other ends of the jumper cables to the same sides of the other battery. The motor barely turned over. So I reconnected the negative battery cable to the battery and touched it with the jumper cable. I got a huge spark, and chickened out. The 12 volt battery was an old battery that I recharged. Maybe it was shorted out? What went wrong? I could have welded with that spark!

 

I recall my father jumping his 40 Ford 1-1/2 ton truck (6 Volt + Ground) with the family wagon (12 Volt - Ground). He would drive the wagon up to the truck so that the steel bumpers made contact, but I don't remember if he made a ground connection with the cables. I wish he were here to ask. He was an electrician and had a couple years of electrical engineering college, so I think he knew what he was doing, and it worked many times. Anyone know of this method?

 

NJ239:
It is quite simple. Just connect the jumper cables like you would if you were going 12 volt car to 12 volt car. I have owned my 6 volt '54 239 since 1977 and I have used 12 volt cars to jump my truck and used my 6 volt truck to jump 12 volt cars many many times with no problems or incidents! As I and others have said above, take off the jumper cables to your 6 volt quickly and first and of course don't let them touch each other.

abe

 

To do it just like 12 Volt to 12 Volt, you would connect positive to positive and negative to negative, so the connection is electrically parallel. That would mean connecting positive 12 Volts to the positve ground of the 6 Volt vehicle and connecting the 12 Volt negative ground to the 6 Volt negative side of the battery. Is this what you have done?

I my father was only using one cable and getting the ground bumper to bumper.

 

No problem can occur if you are positive to positive and neg to neg. I started my stock 6-volt system with a 12volt/6volt battery for years. No harm done at all. If you sparked, it makes me think that maybe you were pos to neg on your hook up. Jag

 

I think that some sparking is normal, which is why you want to make the last connection to a ground away from the battery rather than on the battery post.

 

Another reason for a large spark at hookup is that something is on, like the key or some other switch.