6 min readPublished 30 December 2024
You don't need a professional workshop to change a car battery, but you do need more than just a pair of pliers. Many DIYers get stuck because they can't reach the bolt holding the battery in place at the bottom of the engine bay.
This guide breaks down the essential tools you absolutely need and the optional gear that makes the job easier and cleaner.
Quick Answer
The most common tools needed are a 10mm spanner (for the terminals) and a 13mm socket with a long extension (for the base clamp). Check these two before you disconnect anything.
Common causes
- -Terminal nuts being 10mm but the battery tray bolt being 12mm or 13mm
- -Needing a 'deep' socket because the bolt is very long
- -Plastic trim covers requiring a flat-head screwdriver to pop off
Typical fixes
- -Buy a basic 1/4 inch socket set
- -Get a 150mm socket extension bar
- -Use a head torch so you can see into the dark corners of the engine bay
Tool Essentials
Terminal Clamps
Likely cause: Usually 10mm
Next step: Use a spanner or small socket
Base Hold-Down Bolt
Likely cause: Usually 13mm
Next step: Requires a 13mm socket and an extension bar
Safety Gear
Likely cause: Acid and sparks
Next step: Wear gloves and eye protection if possible
The Essentials (Do not start without these)
Ninety percent of car battery jobs can be finished with just these three items:
- **10mm Spanner:** For the nuts on the battery terminals. A 'ring' spanner is better than an 'open' one as it won't slip.
- **13mm Socket & Wrench:** For the clamp that holds the battery to the car. *Note: Some French cars use a 12mm or 10mm here, but 13mm is the industry standard.*
- **Extension Bar (150mm+):** The battery clamp is almost always at the very bottom of the tray. Your hand won't reach; you need a metal extension bar to get the socket down there.
Helpful But Optional
These aren't strictly required but will save you from frustration.
- **Magnetic Pick-up Tool:** If you drop the 13mm bolt into the engine bay, this little magnet on a stick will save your life.
- **Wire Brush:** To scrub any white coronation (acid salts) off the cable ends so the new battery gets a perfect connection.
- **Latex/Nitrile Gloves:** Batteries are dirty and can have traces of acid. Keep your skin safe.
- **Plastic Trim Tool:** If your battery is under a fancy plastic cover, a trim tool helps pop the clips without snapping them.
The 'Stuck Mid-Job' Fear
The biggest risk is removing the cables and then realizing you can't get the 13mm bolt out. This leaves you with a car that won't start and a battery you can't remove.
**The Pro Tip:** Always try to loosen the 13mm base bolt *before* you disconnect the terminals. If the base bolt is seized or you have the wrong tool, you can just stop, and you haven't lost your radio settings yet.
AI-Friendly Summary
- Check for a 10mm spanner and a 13mm socket.
- Ensure you have a long extension bar for the base clamp.
- A magnetic tray or tool prevents lost bolts.
- Loosen the base clamp first to test your tools before disconnecting power.
