How to Clean Your Battery Terminals
Learn how to clean corroded battery terminals and prevent starting problems. Simple 15-minute job that could save you from a breakdown.
⚠️ Safety First
- • Turn off the engine and remove keys before starting
- • Wear safety glasses - battery acid can splash
- • Remove metal jewelry - rings, watches, bracelets (can cause sparks/burns)
- • Never smoke near a battery - produces explosive hydrogen gas
- • Work in a well-ventilated area
- • If battery is cracked or leaking, do not touch - call for professional help
Why Clean Battery Terminals?
Corrosion on battery terminals creates a barrier between the battery and the electrical system, causing poor connections and starting problems.
- Prevents starting issues: Corrosion stops current flowing properly
- Improves battery life: Clean terminals help battery charge efficiently
- Avoids breakdowns: Quick maintenance prevents problems
- Electrical system protection: Good connections prevent voltage drops
Signs Your Terminals Need Cleaning
- • White, blue, or green crusty build-up on terminals
- • Difficulty starting the car (clicks but won't turn over)
- • Dim headlights or flickering dashboard lights
- • Electrical accessories working intermittently
- • Battery warning light on dashboard
What You'll Need
- Adjustable spanner or socket set (8mm-10mm usually) - to loosen clamps
- Wire brush or battery terminal brush - £3-5 from car parts shops
- Baking soda (bicarbonate of soda) and warm water
- Old toothbrush (for stubborn corrosion)
- Safety glasses
- Rubber gloves
- Clean cloths or kitchen roll
- Petroleum jelly or battery terminal grease (optional but recommended)
Step-by-Step Instructions
1. Prepare Your Work Area
Park on level ground. Turn off the engine, remove the keys, and wait 5 minutes. Open the bonnet and locate the battery.
Put on safety glasses and gloves before starting.
2. Identify the Terminals
Find the positive (+) and negative (-) terminals on top of the battery:
- Positive (+): Usually has a red cover or red cable
- Negative (-): Usually has a black cover or black cable
3. Disconnect the Negative Terminal First
Using your spanner, loosen the nut on the NEGATIVE (-) terminal first. Turn anti-clockwise. You don't need to remove the nut completely - just loosen it enough to lift the cable off.
⚠️ ALWAYS disconnect negative (-) first to prevent short circuits!
4. Disconnect the Positive Terminal
Now loosen and remove the POSITIVE (+) terminal cable in the same way. Position both cables away from the battery so they don't accidentally touch the terminals.
5. Make Cleaning Solution
Mix 1 tablespoon of baking soda with a cup of warm water in a small container. This neutralizes battery acid and helps dissolve corrosion.
6. Clean the Terminals
Dip your wire brush (or old toothbrush) in the baking soda solution and scrub the battery terminals and cable clamps thoroughly.
- Scrub until all white/blue/green corrosion is removed
- The solution will fizz - this is normal (acid being neutralized)
- Use the terminal brush to clean inside the cable clamps
- Wipe away residue with a damp cloth
7. Dry Everything Thoroughly
Use a clean, dry cloth or kitchen roll to dry all terminals and cable clamps completely. Moisture can cause future corrosion.
8. Apply Protective Grease (Optional)
Apply a thin layer of petroleum jelly or battery terminal grease to each terminal. This prevents future corrosion.
9. Reconnect Positive Terminal First
Place the POSITIVE (+) cable back onto the positive terminal. Tighten the nut securely with your spanner. The clamp shouldn't move when you try to wiggle it.
⚠️ ALWAYS reconnect positive (+) first when putting cables back!
10. Reconnect Negative Terminal
Finally, reconnect the NEGATIVE (-) cable to the negative terminal and tighten securely.
11. Test the Car
Try starting the car. It should start more easily than before. Check that all electrical systems (lights, radio, etc.) are working properly.
Important: Always Follow This Order
DISCONNECTING
- 1.Negative (-) terminal FIRST
- 2.Positive (+) terminal second
RECONNECTING
- 1.Positive (+) terminal FIRST
- 2.Negative (-) terminal second
This order prevents accidental short circuits that could damage your car's electrical system.
Preventing Future Corrosion
- Apply grease after cleaning: Petroleum jelly or terminal grease prevents corrosion
- Use terminal protectors: Felt washers soaked in anti-corrosion solution
- Keep terminals tight: Loose connections cause arcing and corrosion
- Check regularly: Inspect terminals every 6 months
- Keep battery secure: Vibration from loose batteries causes terminal damage
After Disconnecting the Battery
Some cars may need settings reset after battery disconnection:
- • Clock/date may need resetting
- • Radio code may be required (check handbook or service book)
- • Electric windows may need recalibrating (one-touch function)
- • Some cars need to "relearn" idle speed - just drive normally for 20 minutes
Track Your Battery Maintenance
Log battery replacements, terminal cleaning, and all maintenance in AutoChain. Keep your complete digital service history.