How to Clean Battery Terminals

Causes for Battery Corrosion

One of the biggest problem faced by car user now a day is the corrosion on the battery terminals. Due to this corrosion charges don’t easily flow through the wires which in return causes problems while starting the engine. In case of sealed lead acid battery (also known as SLA battery or dry battery) corrosion happens when electrolyte makes its way out to battery terminals through any leaks or joints.

Table of Content:
  • Methods to Clean Terminals
  • Baking Soda & Petroleum Jelly
  • Using Professional Grade Supplies
  • Coke

In case of flooded lead acid batteries (wet batteries), electrolyte can jump out while carelessly pouring water into cells. Also, fumes of sulphuric acid which is a part of electrolyte and actually responsible for corrosion keeps arising out of vents of flooded lead acid batteries when battery is charging or hot. Overcharging heats up the battery and heat increases the volume of electrolyte filled inside it. This electrolyte can leak out of vents of overcharged flooded lead acid battery if it is topped up with too much water and also SLA batteries through loose joints. Posts of lead acid batteries are mostly made from lead. Lead itself is a stable metal. Its reaction with sulphuric acid is very slow. If contact happens at battery posts, the compound which is formed as a result of reaction is lead sulphate (PbSO4 ). The chemical reaction between lead and sulphuric acid is accordingly:

Pb (s) + H2SO4 (aq) → PbSO4 (aq) + H2 (g)

Sometimes, it also happens that copper clamps or ringed copper terminals which are used to connect battery with wires corrode. Copper itself is not reactive even if dilute sulphuric acid is poured on it. But when electricity passes, it reacts with sulphuric acid and produce copper sulphate (CuSO4 ) along with water and Sulphur dioxide gas. The equation of this chemical reaction is following:

Cu (s) + 2 H2SO4 (ℓ) → CuSO4 (aq) + 2 H2O (ℓ) + SO2 (g)

The white substance which you see around battery terminals is either lead sulphate made from the reaction explained one paragraph above or anhydrous copper sulphate made from the reaction explained in above paragraph. Anhydrous copper sulphate changes to blue color when water is added to it. The bluish substance which you see around corroded copper terminals or copper clamps is hydrated copper sulphate.

Methods to Clean Terminals

Before cleaning the battery, you need to unplug the battery by following the instructions bellow:

  1. Start by removing the negative cable first.
  2. Place the battery cable wrench on the battery cable end nut and turn it counterclockwise.
  3. If you have a top-post battery, you’ll just need to loosen the nuts until there is no tension on the clamp.
  4. If you have a side-post battery, loosen the cable end until the cable is removed.
  5. Lift the top-post battery cable end off of the terminal. You may have to wiggle and pry the cable end off.

After disconnecting the wires use the methods below to clean car battery terminals.

Baking Soda & Petroleum Jelly

Material needed for cleaning car battery terminal:

  • Baking soda
  • Petroleum jelly
  • Stiff-bristled brush or wire brush
  • Water

Follow these steps to for cleaning battery terminals:

  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.
  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.
  3. Repeat on the cable ends. Perform the same procedure for the battery cable ends.
  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.
  5. Rinse with water. When all the corrosion is removed, rinse the battery and the cable ends thoroughly with clean water.
  6. Let the battery dry completely. You can blow it off with compressed air if you’d like.
  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, yet will protect the battery terminals from corrosion.

Using Professional Grade Supplies

Material needed for cleaning car battery terminal:

  • Battery cleaner spray
  • Battery terminal brush
  • Protective spray or grease
  • Water

Follow these steps to for cleaning battery terminals:

  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 that formed on them. 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.
  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.
  3. 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.
  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.

Coke

This is a bit of an unorthodox method but if you’re in a hurry and have no other option then this can be a life saver to clean corrosion off battery terminals.

Material needed for cleaning car battery terminal:

  • Coke
  • Water

Follow these steps to for cleaning battery terminals:

  1. Pour the coke on the corroded terminal of the battery. Pour the coke slowly on the terminal going center outward.
  2. Rinse the terminal with water to remove the coke residues.
  3. Dry the terminal with a cloth.

Note: use this method only in an emergency as this not one of the best or most suitable method.

How to clean the corroded car battery terminals

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