Starting a 6 volt positive ground car with a 12 volt source

[John Barry [CLC17027]]

If I understand things correctly, it's feasible to jump-start a 6 volt car using a 12 volt source. However, in the instance of a 1940 LaSalle, I'm constantly aware of the fact that it has a positive ground. In this case, I assume that the black (-) cables should be connected to the matching battery terminals on each car. I assume further that the 12 volt source should have the red (+) cable attached to its battery terminal. Finally, the remaining red (+) cable should be connected to ground on the 6 volt car, correct?

It almost goes without saying that all lights, etc. on the 6 volt car should be off, and that the 12 volt source should be disconnected as soon as possible once the 6 volt engine has started.

Comments/corrections are needed. Thanks.

[Cadillac Jack 82]

You have to be very quick about it but yes its possible.

[John Barry [CLC17027]]

That doesn't sound all that safe to me: kind of in the "feasible, but..." category. Thanks.

[Michael Petti]

When I was a kid, my friend had a 1941 Studebaker Commander with 6-volt system. We regularly jumped it from 12-volt batteries because that is what was in most cars in the 60's. Be sure to turn everything off before jumping and disconnect quick. Don't crank the starter too long either. If engine doesn't catch right away, you could damage the starter. We did not damage ours, but we were careful.

[John Barry [CLC17027]]

Thanks: that just reinforced my conclusion.

[Jay Friedman]

I've done it quite a few times over the years.  As mentioned, make sure lights and all other accessories are turned off.  However, the generator, the voltage regulator, the coil and other electrical components that can't be "turned off" could be harmed by 12 volts, so disconnecting the 12 battery quickly is important.  In my experience, however, since it is a DC motor 12 volts won't hurt the starter itself. It will just turn faster, though 12 volts could hurt the starter solenoid.