How to Rejuvenate SLA Batteries
Sealed lead acid (SLA) batteries are the most common type used in today’s automobiles. A SLA battery (also called low or zero maintenance) is essentially the same as older lead acid battery designs, except it is manufactured as a sealed system. A mixture of sulfuric acid and water acts as an electrolyte conducting current between lead electrodes. However, if the plates become coated with sulfur (called sulfation) current flow is blocked. Fortunately, there’s an inexpensive way to remove the sulfur and rejuvenate SLA batteries.
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Things You'll Need
- Safety goggles
- Gloves
- Drill
- Battery Charger
- Crescent wrench
- Plastic funnel
- Distilled water
- Magnesium sulfate
- Baking soda
- Plastic plugs
Instructions
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1
Wear gloves and safety glasses or goggles when you work with lead acid batteries. The sulfuric acid is corrosive and can cause severe chemical burns. Keep open flames away from your work area and make sure it is well-ventilated.
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2
Loosen the battery cables using a crescent wrench and remove the battery from the vehicle.
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3
Locate the “shadow caps” on the top of the SLA battery. These are markings that indicate the place where each battery cell can be opened. Use a drill to punch through each shadow cap.
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Make a solution of about seven ounces of magnesium sulfate (Epsom salt) and one quart of distilled water. It’s easier to dissolve the Epsom salts if you heat the water first. Use Epsom salt you buy at a grocery or other retailer that isn't mixed with other chemicals.
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Place the battery on a three-phase battery charger. Follow the battery charger instructions to attach the leads and set the voltage. Once the battery is connected to the charger, turn the charger on. Allow the battery to charge overnight. A three-phase charger will automatically go to “trickle charge” when the battery nears capacity.
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Turn off the charger and disconnect the battery when charging is complete. Close the drill holes you made with plastic plugs (you can buy these at any auto parts store).
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Reinstall the battery in the vehicle. Make sure the positive (“+”) and negative (“-“) cables are attached to the corresponding terminals and tighten the cables securely. The battery should now function normally.
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Tips & Warnings
Avoid running down your battery. Repeated deep discharges are the primary cause of sulfation. Doing this too often will corrode the lead electrodes to the point the battery cannot be rejuvenated.
It’s a bad idea to simply pour the old battery fluid down a drain. Before you do so, slowly add baking soda to the fluid until it stops bubbling. This neutralizes the acid content. You can then pour the fluid down a drain without harming pipes. Let water run into the drain for a few minutes just to be sure all the old fluid is completely gone.
