How to change a car battery
You can change most car batteries yourself with a couple of spanners. Here's how to do it safely, step by step.
What you need
Get these ready first.
Battery and car
Check these before you buy or start.
- The right new batteryCorrect spec for your car: type (EFB, AGM), capacity, size, polarity, venting and hold-down
- Your radio codeIf your car needs one
!Safety first
Follow these every time you work on a battery.
- Engine off, key out
- Negative (−) off first, back on last
- Keep metal tools off the battery
- No smoking or flames
- It's heavy, so lift with your legs
Tools
Basic hand tools are enough for most cars.
- SpannersUsually 10 and 13 mm
- Gloves and safety glasses
- Wire brush or old toothbrush
Cleaning
For corrosion on the clamps and tray.
- Bicarbonate of soda and waterFor the outside of the clamps and the tray only
- Petroleum jelly
Only if your car maker allows it
Not needed if the car is fully disconnected.
- Battery-support supply
Not sure which battery fits? Battery finder
Step by step
Watch it play, or tap any step.
- 1Park and switch off
Park on flat ground, handbrake on. Switch everything off and take the key out.
- 2Find the battery
It's usually under the bonnet, sometimes in the boot or under a seat. Note which side the + and − are on.
Modern car? Check the maker's procedure first. It will say either full disconnection, or supported replacement with backup power connected. Only use backup power if the maker allows it. See both ways - 3Negative (−) off first
Loosen the black negative clamp and lift it off. Keep it away from the battery.
Why first? If your spanner touches metal now, the risk of a spark is much lower. - 4Then positive (+) off
Loosen the red positive clamp and lift it off.
Backup power connected? The red (+) cable is still live. Insulate it securely so it can’t touch any metal. - 5Lift it out
Undo the hold-down clamp and lift the battery straight up. Keep it upright.
Careful: a car battery weighs 12–25 kg. - 6Clean and fit the new one
Check the new battery is the correct specification for your car, not just the same size: type (EFB or AGM), capacity and cold-cranking rating, terminal layout and polarity, venting and hold-down. Clean the tray and clamps, put it in the same way round, clamp it down and reconnect the vent pipe if there is one.
Corrosion? Wear gloves and eye protection. Use 1 tablespoon of bicarbonate of soda in 1 litre of warm water on the external clamps and tray only. Keep it out of the battery vents, and catch the runoff with a cloth or container. - 7Positive (+) on first
Fit the red positive clamp first and tighten it to the maker's specification.
Don't hammer a clamp on. It can break the terminal. - 8Negative (−) on last
Fit the black negative clamp last and tighten it to the maker's specification.
Why last? With the negative off, there is less risk of a spark while you work on the positive. - 9Start and check
Remove any backup supply, start the car and check that no warning lights stay on. Some cars need a BMS reset, battery registration or coding, or settings relearned. Where required and supported, the applicable procedure is included with your Battery24 battery replacement.
Old battery: bring it to a branch for recycling.
Rather let us do it?
Every fitment includes:
Buy at Brackenfell or Stellenbosch and we fit it free.
We come to your home, work or roadside. Delivery included, within 40 km.
We take it away and recycle it.
Need the right battery?
Send us your car's make, model and year and we'll confirm the battery and price.
WhatsApp us
General guidance for the 12 V battery only, not for the high-voltage battery in a hybrid or electric car. Always follow your vehicle owner's manual. If you don't have the correct procedure or equipment, let a suitably equipped technician do it.