Disclosure: We may earn commissions at no cost to you from qualifying purchases made via the product links in this article.
If your car cranks slowly every time you start it, that could be a sign of corroded battery terminals. You should open the hood or bonnet and inspect the battery. If you see some whitish or greenish substances on the terminals, that’s corrosion and you need to clean it off. Otherwise, the battery will continue corroding and sooner rather than later it will be dead. In this article, you will learn how to clean battery corrosion step by step.
But before you start cleaning, it is good to understand why the terminals are corroding. And here are the two possible reasons. If you find corrosion on the positive terminal, it means that the car battery is overcharging. Probably the alternator is overworking or you don’t draw enough current from the battery to balance charging and discharging.
If the colored substances appear on the negative terminal, it means the battery is not charging fully. This is more common and it indicates either the alternator is bad or not getting enough time to charge the battery fully. Here are some of the things you can do to manage the overcharging and undercharging problems.
How to clean car battery corrosion
After establishing that there is corrosion on the car battery terminals, the next step is to clean them. To do the job, you need the following supplies:
Tools and Supplies
|Rubber or latex gloves||hot water|
|Pair of goggles or safety glasses||battery terminal cleaning brush|
|Baking soda||Vaseline, anti-corrosion spray, or dielectric grease|
|Old tooth brush||Wrench|
|Clean rugs||Battery carrier (optional)|
|A plastic basin or catch can||Small plastic container or disposable cup|
|Plastic scraper or old credit card (optional)||Flat screw driver (optional)|
Step 1: Wear hand and eye protection
Safety comes first when servicing or working around the battery area. You need to protect yourself from corrosive battery acid. To that end, wear latex or rubber gloves to protect your hands and safety glasses to protect your eyes.
Step 2: Remove battery from the car
You may choose to clean the battery while it is still on the car but removing it is safer and more convenient. Start by disconnecting the battery terminals, beginning with the negative terminal.
The reason you disconnect the negative cable first is to avoid shorting the battery when a wrench touches the chassis accidentally while you remove the positive terminal. In vehicles’ electrical wiring, the chassis acts as ground. That is why the positive terminal always has a plastic or rubber cover to protect it from contacting any part of the chassis.
After disconnecting both terminals and keeping them out of the way, remove the battery hold down bar. This is the metal bar on top of the battery that keeps the battery from moving inside the hood.
Now remove the battery. Grab the handle and pull the battery out gently. If the battery does not have a handle, use a battery carrier tool. Otherwise, pull it out gently with both hands and place it inside a large catch can or plastic basin.
Step 3: Scrape the top of the battery with a plastic scraper
Use a small plastic scraping tool to remove dirt and gunk from the surface of the battery. Don’t wet the surface yet. Just take your time and carefully scrape off any corrosion on the surface and around the terminals into the pan. If you don’t have a scraper, you can use an old credit card or any small plastic with a flat edge.
If the battery has vent caps, remove them gently to prevent dirt from entering the cells. use the flat screwdriver to pry the caps from the edges. Scrape off any dirt around the vents, starting from the vent opening outwards. Be careful not to push any debris inside the vent as it could damage the cells. Reinstall the vent caps once the area around the vent openings is clean.
Step 4: Mix baking soda with hot water
Put hot water in a plastic cup or jar and add a few spoons of baking soda. Add about 2 table spoons into each cup of water and give it a good stir. You will see some fizzling as baking soda dissolved in water.
Step 5: Clean the battery surface and terminals
Dip a clean rug into the mixture of water and baking soda, squeeze it a little bit and use it to wipe the surface and posts of the battery. Apply some force when wiping to remove all the corrosion and dirt. Repeat until the surface and the battery posts are clean to your satisfaction.
Step 6: Dip the terminals into a clean mixture of hot water and baking soda
After cleaning all the corrosion on the battery, pour the dirty mixture into the catch pan and make another clean solution. Dip the corroded terminals into the mixture. You should see bubbling as the solution acts on the corrosion material. Let it sit for some time. In the meantime, proceed to the next step.
Step 7: Scrub the battery posts with a wire brush
While you wait for the baking soda solution to act on the battery terminal clamps, grab a battery terminal cleaning tool and start scrubbing the posts. if your battery has top posts, use the female brush to clean off any oxidation. Start with the negative terminal because it is smaller and will not bend the bristle brushes as much. Twist the post cleaner tool until the terminal post becomes evenly shiny. Do the same on the positive terminal.
Step 8: Scrub the terminal ends with a wire brush
Remove the terminal ends from the baking soda solution. Scrub them with an old toothbrush and dip them back into the solution to rinse them. Wipe them dry with a rug and use the male side of the wire brush to clean the surface. The bristle brushes of the wire brush remove any oxidation on the surface.
Step 9: Coat the battery posts and terminal clamps with a thin layer of Vaseline or dielectric grease.
Apply a thin layer of dielectric grease or vaseline on the surface of the battery terminals and posts. to protect them from corrosion. Alternatively, spray anti-corrosion spray.
Step 10: Reinstall the battery
Return the battery into the battery compartment and clamp it down using the battery hold-down clamp. Then install the terminals, this time starting with the positive terminal. Tighten the terminal bolts snugly to create good electrical contact.