Using a correctly sized wrench or socket, loosen the nut/bolt securing the cable on the negative battery terminal.

Always disconnect the negative cable first (before removing the positive cable).

The negative terminal may be marked with a minus (-) symbol, or it may be unmarked. The positive terminal is almost always marked with a plus (+) symbol, often in red.

If the nut or bolt spins without loosening, it may be necessary to counter-hold the opposite side with a second wrench or socket.