What is a Car Battery Terminal Cleaning?
Corrosion can cause starting and charging problems.
Simplified animation — not to scale.
In plain English
Battery terminals are the metal posts on top of the battery where the thick red (positive) and black (negative) cables connect. Over time a white or greenish powdery corrosion builds up around them, caused by acid vapour reacting with the metal. This corrosion creates electrical resistance, which weakens the connection and can lead to slow starting, charging problems and premature battery failure.
"Like cleaning the contacts on a remote control — a thin layer of grime is all it takes to break the connection."
How it works
First, remove the key from the ignition and keep it out — you do not want the engine starting while you are working on electrics. Wear gloves and eye protection. Loosen the negative (black, marked with a minus sign) terminal first using a spanner, then the positive (red, plus sign). Wiggle the clamps gently and lift them off. Mix a tablespoon of baking soda with a cup of warm water and use an old toothbrush to scrub the terminals and inside the clamps until the corrosion is gone. Rinse with clean water and dry thoroughly with a cloth. Apply a thin layer of petroleum jelly or terminal grease to protect against future corrosion. Refit the positive clamp first, then the negative, and tighten firmly. Do not overtighten — you can crack the battery post. Start the engine to confirm everything is working.
Signs of trouble
- ⚠Engine turns over slowly or not at all
- ⚠Battery warning light on the dash
- ⚠Visible white or green powder on the terminals
- ⚠Starter motor clicking but not engaging
- ⚠Battery needs frequent charging or jump starts
Always get a written quote. Prices vary by car, region, and parts brand.