Your car battery’s main role is to allow your engine to start when you turn the key. It is a reserve power source as well, in case there is more demand for power than your alternator can produce while your engine is running. It needs to operate as intended every time you start your car.
Over time and use, corrosion can form on your car battery’s terminals in, on, and around the battery cable ends. The positive cable end connects your battery to the power distribution center that provides power to every system in your vehicle. The negative cable attaches to your car’s chassis to complete the ground circuit. If either one isn’t connected, you won’t have any power to start your car.
Corrosion forms on the terminal for two main reasons:
- The terminal and the cable end are different types of metal
- The battery is off-gassing hydrogen in the charging process
Corrosion shows up in the form of a crusty, fuzzy-looking substance that leaves a mess on your car battery terminals and cable ends. If enough corrosion forms between the cable ends and the terminals, it can actually prevent the battery’s power from flowing from the battery through the cables.
Corrosion on battery connections can be cleaned off using a couple of different methods, and you can help protect your battery from frequent corrosion.
Method 1 of 4: Remove the battery terminals
In order to properly clean your battery terminal connections, you’ll need to disconnect both the positive and negative cable ends from the battery.
Warning: Always wear eye protection and gloves when working with a car battery to prevent accidental injury from battery acid.
Step 1: Loosen the battery cable ends. Start by removing the negative cable first.
Place the battery cable wrench on the battery cable end nut and turn it counterclockwise.
Step 2: Loosen the nuts. If you have a top-post battery, you’ll just need to loosen the nuts until there is no tension on the clamp.
Step 3: Loosen the cable end. If you have a side-post battery, loosen the cable end until the cable is removed.
Step 4: Lift the top-post battery cable end off of the terminal. You may have to wiggle and pry the cable end off.
Method 2 of 4: Clean the battery with household items
You don’t need specialized equipment to properly clean the battery terminals on your car. A few simple household items can clean your battery and restore a proper connection.
- Baking soda
- Petroleum jelly
- Stiff-bristled brush or wire brush
Step 1: Sprinkle baking soda over both battery terminals. Use enough for the powder to coat the terminal with a little around the terminal as well.
Step 2: Pour a couple tablespoons of water on each terminal. The baking soda will react by bubbling up quite ferociously for a couple seconds.
The reaction between the baking soda and water mixture and the acidic corrosion on the battery terminals will neutralize the acid, making it safe to handle.
Step 3: Repeat on the cable ends. Perform the same procedure for the battery cable ends.
You may prefer to perform this step in a small tub or just on top of the battery.
Step 4: Scrub the terminals. Immediately after neutralizing the corrosion, scrub the corrosion off with a stiff brush.
A wire brush is ideal but an old toothbrush will also do in a pinch.
Scrub all around the battery terminal as well as the cable end inside and out.
Step 5: Rinse with water. When all the corrosion is removed, rinse the battery and the cable ends thoroughly with clean water.
Step 6: Let the battery dry completely. You can blow it off with compressed air if you’d like.
Step 7: Smear petroleum jelly on the battery terminals. A thin layer of petroleum jelly will conduct the electricity between the terminal and the cable end, while protecting the battery terminals from corrosion.
Method 3 of 4: Clean the battery with professional-grade supplies
There are products made specifically for the purpose intended here. Battery cleaning equipment and sprays perform an exemplary job quickly and easily.
Step 1: Spray the cable ends. With the battery cables disconnected, spray the cable ends and the terminals with battery cleaner spray.
The spray neutralizes the acid and corrosion. Many sprays have a dye in them that shows up when acid is present. For example, a yellow spray might turn purple in the presence of acid.
Step 2: Soak for a few minutes. Let the battery and cable ends soak in the spray for a few minutes. You’ll notice the color dissipate.
Step 3: Spray again. Spray the battery terminal and cable ends once again lightly with the cleaner spray. If the color doesn’t change or only changes slightly, the acid is neutralized.
Step 4: Rinse with water. Rinse the battery completely with water.
Get all the cleaner spray off the battery and the surrounding areas.
- Warning: Don’t get the battery cleaner spray on your paint job. Some dyes will permanently stain your paint another color.
Step 5: Use a battery brush. Clean the battery posts and cable ends with a battery brush.
For a top-post battery, place the battery brush over the terminal and turn it 3-4 times around the post.
The stiff wire bristles will whisk away any corrosion on the terminal. You can also use a stiff-bristled brush if you have a side-post battery.
Uncap the battery brush and insert the brush into the cable end.
Turn it 3-4 times around as well, removing any corrosion build-up in the clamp.
Step 6: Spray the battery terminals. Spray them with battery protector spray or wipe a thin layer of petroleum jelly onto the terminals.
Method 4 of 4: Reconnect the battery terminals
All you’ll need is your battery terminal wrench to reconnect the cable ends.
Step 1: Replace the cable. Place the positive battery cable end back on.
For top-post batteries, you may have to tap or wiggle the cable end down fully into place.
Step 2: Tighten the nut. Tighten the nut on the clamp until it is snug, then add another quarter turn.
Step 3: Repeat for the negative cable. Install the negative battery cable in the same way.
As you clean your car battery terminals and cables you may notice damage on your battery or cables that requires the attention of a professional. Be sure to contact a certified mechanic, such as one from YourMechanic, who can come to your home or office and service your battery or replace your battery or cables if necessary.
This article originally appeared on YourMechanic.com as How to Clean Battery Connections and was authored by Jason Unrau.