When shutting off power to a conventional 12-volt vehicle battery, which cable should be disconnected first?

• A. Negative cable first, then the positive
• B. Cut both cables at once
• C. Remove the positive cable first
• D. Disconnect the ground strap

Answer: (A)

The main idea is to minimize the risk of a short or spark by breaking the circuit in a way that the vehicle’s chassis isn’t still connected to a live path. The vehicle’s frame is tied to the negative terminal, so disconnecting the negative cable first removes the ground reference. That way, if your tool accidentally touches the chassis and the positive terminal, there’s no complete circuit through the car to cause a spark or arc. After the negative is off, you can safely remove the positive terminal.

Disrupting both cables at once is risky and can cause a sudden arc. Removing the positive first leaves the live path still connected to the chassis, increasing the chance of a short if a tool bridges to metal. The ground strap is basically the negative connection, so relying on that alone isn’t the standard procedure to de-energize the system.