How to Desulfate Batteries

Written by david sandoval
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How to Desulfate Batteries
Battery maintenance is an essential part of car care. (the powerful engine image by kuhar from

The same electrochemical reaction that allows a lead-acid battery to produce electrical energy also damages the internal components of that battery. As the battery discharges, the lead plates of that battery combine with the acidic electrolyte solution to create lead sulphate crystals. These crystals begin to cover the surface of the lead plates, impeding the ability of the battery to produce electrical energy.

When voltage is applied across the battery, these crystals break down into lead and sulphuric acid. This process is called "desulfation." One common way to desulfate batteries is by recharging the battery with a trickle charger.

Skill level:

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Things you need

  • Safety goggles
  • Rubber gloves
  • Battery vent wrench
  • Distilled water
  • Automotive battery
  • Battery trickle-charger

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  1. 1

    Put on the goggles and gloves. Use the battery vent wrench to loosen the battery vent caps. Remove the battery vent caps, and place them on top of the battery case.

  2. 2

    Visually inspect each battery cell to verify that the electrolyte level is sufficient. If the electrolyte level in any of the battery cells is below the "fill" line, pour distilled water into the cell until the electrolyte level reaches the bottom of the "fill" line. Replace and tighten the battery vent caps once all of the battery cells are filled to the correct level.

  3. 3

    Attach the black battery charger lead to the negative terminal on the battery. Attach the red battery charger lead to the battery's positive terminal.

    How to Desulfate Batteries
    Many car chargers are limited to charging at 10 amps or less. (battery charger image by Albert Lozano from
  4. 4

    Plug the trickle-charger into a wall electrical socket. Turn the charger on, and allow the trickle-charger to charge the battery for at least two hours.

Tips and warnings

  • Check the battery every 30 minutes while charging. If the battery gets hot to the touch or begins to bubble, immediately unplug the battery charger and remove the charger leads from the battery.

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