Motorcycle batteries are six-volt lead acid batteries, small versions of the12-volt batteries used in automobiles. If you have a dead motorcycle battery that won’t accept a charge, the problem is normally sulfation. This occurs when a lead acid battery is deeply discharged, causing sulfur from the battery acid to adhere to the lead plates inside the battery and block the flow of electric current. The sulfur also corrodes the lead plates, but as long as the corrosion isn’t severe, you can fix a dead motorcycle battery without spending a lot of money.
1. Take the proper safety precautions. A motorcycle battery contains sulfuric acid, which is extremely toxic. Wear goggles and gloves and work only in a well ventilated area. Keep open flames away from the battery and always allow the battery to cool to room temperature before working on it.
2. Remove the battery from the motorcycle. You’ll probably need to use a small crescent wrench to loosen the battery connectors. Remove the small plastic caps on the top of the battery (called cell caps) and drain the battery fluid completely.
3. Prepare a solution of 8 ounces of Epsom salts (magnesium sulfate) and one quart of distilled water (it’s much easier to dissolve the Epsom salts if you heat the water first to about 130-degrees Fahrenheit). Never use tap water in a battery because it contains chemicals that may damage the battery. Use a plastic funnel to fill each cell of the battery with the solution. Once each cell is filled, shake the battery gently to make sure the solution is well distributed inside the battery.
4. Place the battery on a six-volt trickle charger or a charger with a slow charge option. Do not use a regular charge rate as you would for an automobile battery. Motorcycle batteries are much smaller, and a powerful charging current will damage them and can produce flammable gases. Start with the battery charger off and hook the positive lead to the positive terminal and negative to negative. Leave the cell caps off during charging.
5. Turn the charger on low the battery to charge overnight or until the charger indicator says charging is complete. Then turn the charger off, remove the Leeds, and replace the cell caps. Reinstall the battery in the motorcycle, making sure the connectors are secure. The battery should now operate normally.