Battery Disconnect Switch

[Ralph E.]

Why is the green knob type battery disconnect switch attached to the negative(-) terminal and not the positive(+)??

[Joe T.]

Re: Battery Disconnect Switch

i believe that you can get arcs of current between the battery and metal components if you don't disconnect the negative

[Doug Flaten]

Re: Battery Disconnect Switch

You can pull the positive terminal and a car will run off the generator /alternator. Disconnecting the negative terminal will kill a car dead. I experienced it once on the road when the ground strap bolt vibrated out. It is a bit weird to see everything on the gauges shut down all at once while you are cruising along.

[John H.]

Re: Battery Disconnect Switch

Because when it's on the ground terminal, it totally eliminates the ground path back to the battery, which makes it impossible to create a short or make a spark anywhere in the car, even if you drop a wrench and one end hits the positive terminal and the other end hits the engine or the frame. If you put it on the positive terminal and drop a wrench on it, the ground path back to the battery still exists, and you can still get a direct short/spark. The only way to "kill" all the power to the grounded components is to eliminate the ground path back to the battery.

[Ronnie Robertson # 36786]

Re: Battery Disconnect Switch

In DC (direct current) electricity, the electron flow is from the negative to the positive. Placing the switch on the negative post provides a way to eliminate any electrons from escaping the battery. If the switch was on the positive post, electrons would flow from the negative battery post throughout the enabled circuits and stop at the switch on the positive post. Generally speaking, placing the switch on the negative post reduces the probability of accidental short circuits.

[Ralph E.]

Re: Battery Disconnect Switch

Thanks ALL. Now I don't feel so dumb. Sometimes basics need to be explained.