How to Disconnect and Change a Car Battery

Learn about the steps involved in disconnecting and changing a car battery to avoid safety risks right here in Savvy’s handy guide.

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, updated on August 14th, 2023       

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Disconnecting and changing a car battery is a simple yet essential skill which every car owner should know. Whether you need to perform maintenance, replace the battery or ensure safety during repairs, learning the proper procedure is crucial. In Savvy’s comprehensive guide, you can walk through the step-by-step process of disconnecting a car battery, emphasising safety measures and learning useful tips to make the task easier.

How do I disconnect and change my car’s battery?

Safety first

Before proceeding with any battery-related tasks like replacement or disconnection, ensure your safety by taking the following precautions:

  • Park your car on a flat surface and engage the parking brake.
  • Turn off the engine and remove the ignition key to avoid any electrical risks.
  • Put on safety goggles and gloves to protect your eyes and hands from any chemicals and potential sparks.

Identify the battery terminals

Pop open the bonnet and locate the car battery. Most car batteries are situated near the engine compartment, enclosed in a plastic or metal box. Once you find the battery, take a closer look to identify the positive and negative terminals. The positive terminal typically has a red cap or a plus sign, while the negative terminal is usually black with a minus sign. It’s important to know which terminal is which for several reasons, such as if you ever need to jump start your car.

Disconnect the negative terminal

It's crucial to disconnect the negative terminal first to reduce the risk of electrical shock. Use a proper-sized spanner to loosen the nut securing the negative terminal. Once the nut is loose, carefully lift the negative cable off the terminal. To prevent accidental reconnection, wrap the cable end with a cloth and secure it away from the battery.

Disconnect the positive terminal

Next, proceed to disconnect the positive terminal. Follow the same steps as before, using the spanner to loosen the positive cable. Gently lift the cable off the terminal and secure it away from the battery, ensuring it doesn't come into contact with any metal parts.

Inspect the battery

With both terminals disconnected, take this opportunity to inspect the battery. Check for any signs of corrosion or damage, such as leaks or cracks. If you notice any issues, it's best to address them promptly to prevent future complications. This may involve seeking professional help if you aren’t comfortable dealing with this yourself.

Clean the battery terminals (optional)

If you see corrosion on the battery terminals, you can clean them using a mixture of baking soda and water. Apply the mixture to the terminals and use a wire brush to scrub off the corrosion gently. Rinse with clean water and dry thoroughly before reconnecting the battery.

Reconnect the battery

After performing any maintenance or repairs, it's time to reconnect the battery or connect the new battery. Start by connecting the positive cable to the positive terminal, followed by the negative cable to the negative terminal. Tighten the nuts securely to ensure a stable connection.

Test the battery

Once you've safely reconnected the battery, turn on the ignition and check if all electrical components are functioning correctly. Test the lights, radio, air conditioning and other features to verify that the battery is supplying power as expected.

When might I need to disconnect my car’s battery?

There are several situations in which you might need to disconnect your car's battery:

  • Vehicle maintenance: when performing maintenance tasks which involve electrical components or systems, disconnecting the battery is a safety precaution. It prevents accidental electrical shocks and protects sensitive electronics during repairs.
  • Battery replacement: if your car battery needs replacement, you must disconnect it before removing and installing the new one. You’re likely to experience this at least once in your time owning a car, as batteries generally last between three and five years.
  • Recharging the battery: in the event your car’s battery is unable to be properly recharged inside your vehicle, you may have to remove it and charge it separately.

Always remember to follow safety precautions and proper procedures when disconnecting or reconnecting your car's battery to avoid any mishaps, such as damage to your vehicle or injury to you or anyone else working on the vehicle with you.

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