How To Clean A Car Battery

If you are having trouble starting your car, the battery is the first thing that you should check. Batteries lose charge over time, and eventually they degrade so much that they cannot be recharged. There are other things that can go wrong with a car battery though, and one of the most common issues is corrosion of the terminals. Often, simply cleaning a car’s battery will make a difference to its power output.

How to clean a car battery

Corrosion on a battery terminal is quite easy to identify. It manifests itself as a salty crust on and around the exposed metal that sits on top of the battery. The metal posts are the battery “terminals”, and these are what the wires are connected to (usually by strong metal clips. Cleaning these will prevent a lot of problems with your battery.

Before you try to clean a car battery, make sure that the battery is undamaged. If you see any cracks, swelling, leaks or other signs of damage, don’t clean the battery. Don’t try to move a leaking or damaged battery either. Get an expert to come out and look at it, because there’s a very high chance that the battery will need replaced.

Before you start to clean a car battery, you should take some safety precautions:

  • Perform a visual inspection of the battery. If there are any signs of damage, call an expert.
  • Wear eye protection and gloves before you start working on the battery. Both the corrosion itself and battery acid are highly dangerous.
  • Make sure the car is not running and any electrics are off.
  • Take a photo of the battery so you know where the contacts go.
  • Disconnect the negative (black) contact first, and then disconnect the positive.
  • Clean the terminals using the instructions below.
  • Make sure that the battery is dry.
  • Reconnect the positive terminal, then the negative terminal.

Cleaning car battery terminals

You don’t need any specialist solutions to clean a car battery. A mixture of baking soda and water will do the job. You should make the mix quite strong - lots of baking soda and a small amount of water.

Use a wire brush (or a hard-bristled toothbrush if you don’t have a wire brush) to apply the mixture to the exposed metal parts of the battery terminals. The mixture will start to fizz. This is a good thing and means that the corrosion is breaking down.

Scrub vigorously to remove the corrosion. Once you are satisfied, use some clean water to rinse off the terminals. Don’t soak the battery in water, use just enough to clean it. Wipe the battery dry with a soft rag or some paper towels.

You can protect the battery from corrosion in the future by coating the exposed metal parts of the battery with a small amount of grease.

How to clean corrosion on a car battery

If a toothbrush and baking soda won’t do the job, you may find that coca cola is powerful enough to break down the corrosion. Alternatively, you may need to use a steel brush.

For particularly stubborn areas of corrosion, try sprinkling the baking soda directly onto the corroded terminals, then pouring a couple of tablespoons of water onto the terminal. This should cause quite a fierce reaction, neutralizing the acidic corrosion, and making it easy to scrub off.

If baking soda is not powerful enough, you can buy professional-grade battery cleaning sprays. These are much more effective at neutralizing the acid and breaking down the corrosion. Many of the sprays have a dye in them which will change colour when it comes into contact with acid. This gives you a good visual guide to show that the spray is working.

To use battery cleaning spray:

  • Disconnect the cables from the battery (negative first)
  • Spray the cleaning spray directly onto the corroded terminals.
  • The spray should change colour in the presence of corrosion.
  • Let the spray soak into the cable ends/terminals, until the colour dissipates.
  • Spray the cable ends/terminals again and watch to see if it changes colour. If it does, repeat this process.
  • When the spray does not change colour upon application, this means the acid is neutralized.
  • Rinse the battery with water, and then scrub it with a toothbrush or wire brush to remove the corrosion.
  • Reconnect the battery cables (positive cable first).

Don’t forget that the terminals themselves are not the only areas where there will be some corrosion. The battery cable ends and connector tips will also have some corrosion on them. Depending on how long the cables are and how bad the corrosion is, you can either clean them on top of the battery, or in a small tub containing a solution of the water and baking soda.

Pat the cables dry once you have finished cleaning them, and then reconnect them to the battery – positive first, and then negative.

Whether you are using baking soda or professional cleaning solutions, always wear protective clothing while working on or around a car battery. If battery acid gets in your eyes, it could cause blindness, and even the flakes of corrosion could burn your skin. Keep children and pets away from your car while you are working on it.

If your car still does not start after cleaning the battery, test the battery with a voltmeter. You may need to recharge the battery. If your car battery is more than a few years old then it may no longer be in a good enough condition to hold a charge, and you should replace it as soon as possible. Do not put off replacing a damaged or depleted car battery; old batteries put strain on your alternator, and replacing a damaged alternator costs a lot more than replacing a damaged battery.

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