How to Clean Car Battery Terminals Safely

Corrosion on battery terminals is common, especially in damp climates like the Lower Mainland. The crust gets in the way of the electrical connection, which can cause slow cranking or a car that will not start even with a healthy battery.

Before you start

• Turn the engine off and take the key out.
• Wear safety glasses and gloves. Battery corrosion can irritate skin and eyes.
• Keep sparks, flames and metal tools away from the top of the battery.
• Check the owner's manual first. Some vehicles have special rules about disconnecting the battery, and many newer cars lose settings or need the battery registered afterwards.

Cleaning steps

1. Disconnect the negative (black, minus) clamp first, then the positive (red, plus).
2. Mix a spoonful of baking soda with water and brush it onto the corrosion with an old toothbrush or a terminal brush. It will fizz.
3. Wipe it clean with a damp cloth and dry everything well.
4. Reconnect the positive clamp first, then the negative, and make sure both are tight.
5. A thin layer of dielectric grease or a terminal protector on the posts helps slow new corrosion.

When cleaning is not enough

If the terminals are badly eaten away, the cable ends are damaged, or the case is swollen or leaking, stop. Those need a proper inspection, and the battery may need replacing. If the car still will not start after cleaning, the battery or the charging system should be tested.