How to Clean Corroded Car Battery Terminals (Without Removing)

Co-authored by Duston Maynes

Last Updated: March 9, 2024 Approved

Many drivers experience difficulty starting their vehicles at some point or another. Sometimes, a major part is to blame, but a lot of times this frustrating event is caused by buildup on the battery terminals. Learning how to clean corroded car battery terminals will avoid unnecessary expenses and worry.

Method 1

Method 1 of 2:

Cleaning with Baking Soda

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1
Determine the terminal configuration of your battery. There are two types.^{[1]
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- If the terminals are on the side, you will need a 5/16-inch (8 mm) wrench to loosen both cable nuts.
- If the terminals are on top of the battery, you will need either a 3/8-inch (10 mm) or 1/2-inch (13 mm) wrench.
This will reduce the likelihood of accidentally grounding the cables.

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3
Loosen the nut on the negative (-) cable clamp. Unfasten the cable from the post.^{[2]
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- Do the same for the positive (+) cable. If you have trouble removing either cable, attempt to twist them while pulling up at the same time.
If any are found, you need to replace the battery.
If a large rip is found, you may have to replace these parts.
6
Mix 1 tablespoon (15 ml) of baking soda with 1 cup (250 ml) of very hot water. Dip an old toothbrush into the mixture and scrub the top of the battery to remove corrosion buildup.^{[3]
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- You can even dip the ends of the battery cables in hot water to dissolve any corrosion on the cable ends themselves.
- The buildup is acidic and can burn your skin. To avoid it, wear gloves and safety glasses.
Remember to soak your brush in the baking soda solution as much as needed.
Make sure all the baking soda and corrosion is washed away. Dry the battery and clamps with a clean cloth.
Use petroleum jelly or a commercial battery terminal protection spray.^{[4]
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10
Reattach the positive (+) cable clamp to the proper terminal. Tighten the nut with your wrench.
- Repeat with the negative (-) clamp. Test if terminals are tight enough by twisting each one by hand.

Method 2

Method 2 of 2:

Emergency Cleaning

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Do not entirely remove the cables.
Repeat going in the opposite direction.
Tighten the terminals and try to restart the car.

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Tips

You can purchase a battery cleaner spray. Some include an acid detector in the formula. These tend to be less time-consuming, but you must read the directions on the bottle, because each one is different.

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You can use a battery terminal brush or sandpaper if the buildup is too heavy for a toothbrush.

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Warnings

The negative cable should always be removed first and attached last to prevent arcing.

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Always wear protective gear.

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Remove all jewelry before starting work. Rings and bracelets can become grounded or get caught on engine parts.

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