Lift the lid that covers the battery cells, and fill the cells with distilled water if they are dry or low on water. Hook the battery up to a rejuvenator, and allow the battery to fully charge. To ensure a full charge, slowly discharge the battery, and place it on the rejuvenator to bring it to full charge a second time.
Another option is to clean any corrosion off the battery using a combination of 2 tablespoons of baking soda and 1 quart of distilled water. Use a paintbrush to apply the baking soda solution to the corroded areas, and rinse with a paintbrush dipped in clean water.
Open the lid that covers the battery cells, and fill the battery cells with a solution made with 8 ounces of Epsom salts and 2 quarts of distilled water. Set a battery charger to the recommended voltage, and allow the battery to charge overnight. Replace the battery if it does not charge.
Reconditioning is only recommended for lead acid batteries, and the reconditioning process should be completed outdoors. Do not allow corrosion to touch the skin, and wear safety goggles and gloves to prevent injuries. Do not use tap water to recondition batteries.