Golf cart batteries are small 6-volt versions of the 12-volt lead acid batteries used in cars. Lead acid batteries are very reliable unless they are deeply discharged (run down) too often. This causes sulfur to collect on the lead plates inside the battery. This "sulfation" blocks current flow so the battery can't charge. It also corrodes the lead plates, but if the damage isn't too severe you can repair a golf cart battery inexpensively using magnesium sulfate, a common household chemical better known as Epsom salts.
Step 1
Place safety first by wearing safety glasses and gloves when working with lead acid batteries. The acid is very corrosive and can cause serious chemical burns. Work in a well-ventilated area and keep open flames away from the battery.
Step 2
Disconnect the battery cables using a crescent wrench and remove the battery from the golf cart. Remove the cell caps (the plastic caps on top of the battery) and carefully drain all of the fluid into an acid-resistant container (available at auto parts and hardware stores). Neutralize the acid in the fluid by adding one tablespoon of baking soda at a time until the fluid stops bubbling. Dispose of the fluid by pouring it down a drain and allowing water to run for five minutes to flush the drain completely.
Step 3
Mix a solution of 4 oz. of Epsom salts in a pint of distilled water and stir until the Epsom salts are dissolved (if you heat the water first this is a lot easier). Always use distilled water. Tap water may contain chemicals that will damage the battery. Use a funnel to fill each cell of the battery with the solution. Shake the battery gently to make sure it's well distributed.
Step 4
Use a three-phase battery charger to recharge the battery. These are designed for lead acid batteries and will automatically slow charging as the battery nears full charge, preventing overcharging. Make sure the charger is turned off and connect the positive lead to the positive battery terminal (marked with a "+" sign) and the negative lead to the negative terminal (marked with a "-"). Set the charger to six volts and turn it on. Allow the battery to charge overnight.
Step 5
Turn the charger off when the golf cart battery is completely charged. Disconnect the charger leads and replace the cell caps. Reinstall the battery in the golf cart, making sure the battery cables are securely fastened. The battery should now function normally. It's a good idea to repeat the charging process in a few days to ensure maximum performance.