Switch the car off and remove the key. Then disconnect the negative (−) terminal first, usually black, followed by the positive (+), usually red. Tuck the leads away so they can't touch the battery posts. When reconnecting, do the reverse: positive first, then negative. Check your handbook first, as some cars need specific steps.
Before you start
- Read your handbook. Some cars have the battery in the boot or under a seat, and some have specific disconnection procedures.
- Make sure you have your radio or security code if your car needs one.
- Wear gloves and eye protection, and remove metal jewellery.
- Switch the car off and take the key out.
Step by step (RAC)
- Open the bonnet and find the battery. It may be under a plastic cover.
- Identify the terminals. Positive (+) is usually red. Negative (−) is usually black or blue.
- Loosen the negative terminal nut with the correct spanner, lift the clamp off and tuck it away.
- Do the same for the positive terminal.
Why negative first?
Taking the negative (earth) off first means that if your spanner touches the car body while you work on the positive terminal, it won't create a short circuit.
Reconnecting
Positive first, then negative, and make sure both are tight (RAC). If the terminals are crusty, clean them first. See corroded battery terminals.
If you're replacing the battery
The RAC notes that many modern cars need battery registration or electronic system resets after a new battery is fitted. If you'd rather not do it yourself, Jump Start Car fits batteries on site from £150, including the battery. See battery replacement.
Frequently asked questions
Which terminal do I take off first?
Negative (−) first, then positive (+).
Which terminal goes back on first?
Positive (+) first, then negative (−).
Will I lose my settings?
You may lose radio presets, the clock or other settings. Check your handbook for any codes you'll need.