How to Restore Car Battery Acid

Written by paul dohrman
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Suppose you spill sulphuric acid out of your car battery somehow. Or maybe you've measured the voltage and it's significantly below 12 volts. You might think that restoring this lost acid is a matter of buying acid solution and pouring it in. Actually, the chemistry is subtler than that. You can acidify a solution by dropping in salt---in this case, magnesium sulphate. Sulphur has accumulated on the plates over time and that serves as a sulphur source as well.

Skill level:
Moderately Challenging

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Things you need

  • Epsom Salt
  • Gloves
  • Safety glasses
  • Battery charger
  • Drill
  • Charger

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  1. 1

    Put on safety gloves and glasses. Turn off the ignition, remove the car battery from its cables and place it in a well ventilated place to work on.

  2. 2

    Remove the plastic cell caps if the battery is serviceable. If it's sealed, use a drill on the top plastic to open each cell. The battery will have "shadow marks" where the top of each cell is. You'll plug these holes with hole caps that you can find at any hardware store.

  3. 3

    Heat a quart of distilled water in your microwave, though not to boiling. Around 65.6 degrees C is right. Mix in 10 tbls. of Epsom salts (magnesium sulphate).

  4. 4

    Pour this solution into the holes in the battery, filling them up to the marked levels on the battery.

  5. 5

    Charge the battery overnight with a charger you plug into a wall socket. This is advisable because a car's alternator works well only if the battery has not been deeply discharged. A charger that performs three-step regulated charging is the best.

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