The Stovebolt Site Forums The Shop Area The Electrical Bay Jumping a 6V

Gents,

I have buddy that had vehicle troubles in the past. Will it hurt a 6 V truck if I jump it with a 12V truck? I assume it could hurt the gauges and all. I believe my buddy has a bad ground issue.

Just looking for an alternative if we can’t push start it.

Chris

A short boost with 12V isn't likely to hurt gauges, etc. but there is some danger involved. As soon as the jumper cables are connected, the 6V battery will receive a quick burst of current which will make it generate a lot of Hydrogen gas. A spark near the top of the battery can ignite that gas, causing an explosion. To avoid problems, connect the first cable to the "hot" side of both batteries, but make the final connections somewhere else, such as engine block to engine block, etc. Any spark that gets generated will be away from the batteries. That's also a good rule of thumb to follow when both vehicles are 12V. Also pay attention to ground polarity- - - -most GMC's are Positive ground so it's easy to get the polarity reversed. That really creates some fireworks!

The 6V is a 1952 Chevy panel with a 216 in it.

Thank you! Just to be safe, I will get strong and push hard! Last resort will be jumping it!

Chris

Just hang a used tire on the front bumper of your truck and let the engine do the pushing. I've ferried cars home that way for many miles, back when vehicles had real bumpers!
Jerry

Here is a Jim Carter tech article on how to jump a 6 volt electrical system.
Applying 12 Volts to a 6 Volt Starter

Excerpt from article.
DANGER: Jumping 6 volt vehicle with a 12 volt battery can be done at a “maximum” of 15 Seconds! After that the solder in the commutator begins to melt, some wiring insulation is turning black, and the starter switch may be turning blue. Connect the 12 volt cables “ONLY” when you are ready to start the engine. Have a person ready to immediately to remove one of the 12 volt cables the second it becomes running. Remember: Not over 15 seconds or parts of your 6 volt system are cooked.

Even at its rated voltage, a starter runs at an extreme overload, virtually a dead short. Doubling the voltage also increases the current flow, so if you're cranking in bursts of 5-10 seconds, it's a lot easier on the starter. A continuous duty motor with the power of a starter would need to be approximately the same size and weight of the engine. If the engine doesn't start after a total cranking time of 30 seconds, (six 5-second attempts, for instance) let the starter cool down for a minimum of 20 minutes before trying again.
Jerry

ndkid275, everyone is right. I'm frequently made fun of because almost all my six volt vehicles are just that six volt. I held a class out at OLD TOWN in Kissimmee, FL. The not so secret method is 2 flat cable's or heavy six volt coated cables and wire brush everywhere to a silver shine where connections occur. Use a little No-Ox or battery grease on connection. Do this twice a year. Oh, if I might suggest, I have two deep charge six volt batteries connected in series. This is not always possible on many applications, my batteries are under the floor so I just lengthened my battery tray and used skate board wheels on frame runners to tuck them in. Doc.

Uhhhh- - - - -Doc- - - -if they're in series you've got 12 volts. Do you mean "parallel", maybe?
Jerry

Doc,

It’s not my vehicle. I just want to be able to assist if possible.

Jorb,

I am running a 6V starter on a 12v system. Original ignition and all. Only change was gauges. Been running it like that for 3 years now without issue.

Chris

I’ve jumped a dead 6v with a 12v several times and all I can say is make it as fast as you can, the jumper cables get hot pretty quick. And as soon as it starts, disconnect it asap. It didn’t hurt a thing on my 1940 1.5 ton. I’ve since replaced the dead 6v battery and so I. I longer need to do this, but I’ve done it 4-5 times successfully without hurting anything. I’ve also used a 12v battery to jump my 1942 ford tractor several times and it didn’t hurt that 6v battery at all.

It is amazing how easy these engines start with a slight push. I have put mine in second gear with the clutch pushed in, and let it roll down my short driveway and let the clutch out all at once. It fires right up before it reaches the street, especially if I remember to turn the key on first.