Questions and Answers

Automotive Jump-Starting Questions Q. Hi guys. Thanks for the article on DIY: Jump-Start a Car. Recently I helped two girls jump-start a vehicle. Luckily, we got it started, but let's just say they weren't very impressed with my technical knowledge. The next time I assist two cute females in such a matter, I want to knock their socks off with my knowledge and ability.

Maybe you could provide some more information on the details of jumping a vehicle for those of us who are curious.

1. WHY is it a bad idea to connect the negative cable to the negative terminal of the dead vehicle? I ended up doing this, and it worked. What are the potential consequences of connecting the batteries directly like this?

2. WHAT in the world is going on when you connect the negative terminal to the engine block of the dead car? I thought electricity needed a complete CIRCUIT to flow. Surely there is not a complete circuit through the actual engine/body of the dead vehicle, so what is going on there?

3. WHY do you connect the cables in the order specified? Will something bad happen to me if say I connect both cables to the dead vehicle first, before connecting anything to the live vehicle? What are the potential pitfalls?

Thanks!
Geoff

A. To answer your questions in order:

1. Batteries contain hydrogen gas, very explosive. You do not connect the negative cable to the negative battery terminal of the dead vehicle because there is a very good chance the sparks will ignite the hydrogen gas and cause an explosion.

That would definitely ruin your day and any chance of scoring. By connecting the cable to the engine block, you significantly lower the chances of a battery explosion.

2. You are correct, electricity does need a complete circuit to flow. In the case of a car, the frame and engine, which are made of metal, acts exactly as a wire. This serves the main purpose of reducing the amount of wire in a car almost in half. In addition you can connect to it at any point.

Back in the days when cars had metal bumpers and I would go out on a road call to start a dead car instead of having to get nose to nose, sometimes a dangerous position to get into, I would clip my cables together then simply touch the bumper of the tow truck to the bumper of the car I was jump-starting.

Since the bumpers were mounted to the frame, and the frame was connected to the batteries, the vehicle frames were the ground and the negative cable wasn't needed. Incidentally, this is the safest way to jump-start a vehicle.

3. Again, the order is to prevent sparks from igniting the hydrogen gas and causing a battery explosion.

And Geoff, in my years I have found the best way to impress a Lady is to treat her with dignity and respect. To talk to her, not at her. To open a door for her and to hold her seat when she sits.

And most importantly, when you talk to her, look in her eyes, not at her breasts.