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Before you start — the safety points battery manufacturers require
A lead-acid battery vents hydrogen while charging, and GS Yuasa notes that hydrogen is explosive above 4% concentration in an enclosed space. Work in a well-ventilated place, and never smoke, use a naked flame or create a spark near the battery.
The electrolyte is sulphuric acid — corrosive to skin, eyes and clothing — so wear eye protection and gloves.
Remove rings, watches, bracelets and necklaces before you start. A metal object bridging a terminal to the bodywork will short the battery and can weld itself in place. Disconnect the negative terminal first and reconnect it last, for the same reason.
Batteries are heavy (15–25kg), and they are not always under the bonnet. On many hybrids and some diesels the battery sits in the boot, under the rear seat or under the floor, and the engine bay may carry only a remote jump-start terminal — check where yours is before you begin.
Tools Needed
- 10mm and 13mm spanners or sockets
- Wire brush or battery terminal cleaner
- Petroleum jelly or terminal protector spray
- Memory saver (optional but recommended)
Step-by-Step
- Turn off the ignition and remove the key.
- Connect a memory saver if you have one (preserves radio code and settings).
- Disconnect the negative (-) terminal first using a 10mm spanner.
- Disconnect the positive (+) terminal.
- Remove the battery hold-down clamp (usually 13mm).
- Lift the old battery out — they’re heavy (15-25kg).
- Clean the terminals and battery tray with a wire brush.
- Place the new battery in the tray and secure the clamp.
- Connect the positive (+) terminal first.
- Connect the negative (-) terminal last.
- Apply petroleum jelly to both terminals to prevent corrosion.
Start-Stop Battery Registration
If your car has start-stop, the battery management system (BMS) needs to know a new battery has been fitted. Without registration, the BMS still thinks the old battery is fitted and won’t charge the new one correctly, leading to premature failure.
Frequently Asked Questions
Is replacing a car battery dangerous?
It is a straightforward job, but it is not risk-free, and battery manufacturers publish specific warnings. A lead-acid battery vents hydrogen, which GS Yuasa notes is explosive above 4% concentration in an enclosed space, so work somewhere well ventilated and keep sparks, flames and cigarettes well away. The electrolyte is sulphuric acid, so wear eye protection and gloves. Remove rings, watches, bracelets and necklaces first, because a metal object bridging a terminal to the bodywork will short the battery and can weld itself in place. Disconnect the negative terminal first and reconnect it last. The battery itself is heavy, typically 15-25kg.
Will I lose my radio code?
Possibly — disconnecting the battery resets volatile memory. Use a memory saver or have your radio code ready. It’s usually on a card in your handbook.
How often should I replace my car battery?
Every 4-6 years on average. Start-stop vehicles may need more frequent replacement (3-5 years) due to the higher cycling demands.
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How we check fitment for this guide
We cross-reference fitment figures against manufacturer specifications and OE-supplier catalogue data where available, and matched to the standard codes that actually govern fit — battery type/group sizes, wiper lengths and fitting types, bulb fitment codes, tyre size markings, and oil specifications. We work by make, model, year, engine, and build date, because a single model can take different parts across its life. Where the right part depends on your exact vehicle, we tell you to confirm by registration or VIN. More on our method →