Last updated 2020-05-28

Disconnect a car battery

Steps to disconnect a car battery.

Prerequisites

Before disconnecting a battery

  • the following tools are required:
    • wrench, and
    • wire battery terminal brush, and

  • the following safety equipment must be worn:

    • safety goggles
    • long-sleeved rubber gloves or work gloves
    • safety footwear, and
    • long pants.

Refer to the Health and wellbeing resources and Safety at work procedures for additional information.

When this applies

Batteries must be disconnected whenever there is the potential for a battery to cause a fire or explosion. You have determined it is safe to disconnect the battery, and you are able to do so. Follow the vehicle manufacturer’s recommended disconnection procedures if available, or these steps, even if the battery has no charge.

When disconnecting the power sources in Electric Hybrid Vehicles follow the vehicle manufacturer’s electrical system disconnection procedures.

Procedure

  1. Ensure it is safe to disconnect the battery.
  2. Locate the battery.
  3. Identify the positive and negative terminals.

    If the terminal says...

    Or shows this symbol...

    Then the terminal is...

    POS

    +

    positive.

    NEG

    -

    negative.

  4. Inspect the battery for a green and white ashy substance (signs of corrosion) on and around the terminals and wires.
    If there are ... Then ...
    signs of corrosion use a wire brush to remove corrosion
    no signs of corrosion proceed to step 5.
  5. Use the correctly sized wrench to loosen the nut at the side of the negative terminal. When the nut is loose, twist the terminal off the negative post.
    Important: Always disconnect the ground (negative (-) usually black) cable from the battery first.
  6. Remove the positive terminal from the positive post.
    Note: The positive cable is usually red.
  7. Repeat steps 2-5 until all batteries are disconnected.
  8. Ensure the cables cannot come into contact with the battery terminal or any part of the vehicle.
  9. Use a yellow oil marker to mark the vehicle B/D to indicate that the battery has been disconnected.

    If the front windshield of the vehicle...

    Then...

    is intact

    mark the windshield.

    is smashed

    mark the driver’s side of the vehicle.

  10. Proceed according to whether the vehicle is repairable.
    If the vehicle is ... Then ...
    repairable place or hang a Notice to Customer (CL338) inside the vehicle.
    not repairable follow total loss procedures.
Parent topic: Safety considerations