How to Chemically Desulfate a Car Battery

Updated March 23, 2017

Car batteries act as the nerve centre of your car by providing the initial spark of energy to engage the vehicle's internal combustion engine. Thus, if your battery doesn't work, your car doesn't work. Car batteries contain metal plates and are filled with sulphuric acid, which aids in conduction of the electric charge. Continual use of the battery, in combination with the presence of sulphuric acid, causes the formation of a hard, solid sulphate precipitate on the battery parts. Removing the precipitate helps extend your battery's life.

Heat 1 quart of distilled water until it reaches a rolling boil. Remove the water from the heat source. Add 1 cup of Epsom salt to the water and stir until the salt dissolves.

Detach the positive and negative terminals of your car battery. Remove the battery from your car. Put on your rubber gloves and safety glasses.

Place the car battery in a ventilated area. Unscrew the lid from the top of the battery. Use the plastic siphon to remove all of the sulphuric acid solution in the battery cells.

Pour the Epsom salt solution into the battery cells until the plates are covered completely. Screw the top back on the battery and gently shake the battery back and forth. Reinstall the battery in your car.


Always wear protective gear when tinkering with a car battery. Sulphuric acid is harmful if it comes into contact with your skin. Do not remove your car's battery while the vehicle's engine is still running because this can cause a life-threatening electrical shock.

Things You'll Need

  • 1 cup Epsom salt
  • 1 quart distilled water
  • Rubber gloves
  • Safety glasses
  • Plastic siphon
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About the Author

Andrew Mayfair has written professionally since 2009 when his article on patent law was published in the "Loyola of Los Angeles Entertainment Law Review." Mayfair earned his Bachelor of Science in biochemistry from the University of California, Davis and his Juris Doctor from the University of the Pacific, McGeorge School of Law.