How to Desulfate Batteries

Updated February 20, 2018

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.

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.

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.

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.

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.


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.

Things You'll Need

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

David Sandoval has served as a trainer and technical writer since 2000. He has written several articles online in the fields of home improvement, finance, electronics and science. Sandoval has an Associate of Applied Science in microelectronics from Northern New Mexico College.