Six-volt batteries are smaller versions of the lead acid 12-volt batteries used in most cars. However, because six-volt batteries are often found in vehicles and appliances that see limited use, they are frequently neglected. Proper maintenance and charging will improve performance and extend their useful life. You should avoid completely draining (deep discharging) a six-volt battery since this will also shorten the battery's life. When you charge a six-volt battery, take the proper safety precautions. The acid in the battery is toxic and can cause burns and eye damage, and is poisonous if swallowed.
Choose a battery charger that fits your needs. Chargers for six-volt batteries typically run $20 to $50, although high-end units can cost over $100. A "smart" charger (one with a microprocessor) can switch to a trickle charge mode when a battery is fully charged to keep it at optimum charge when stored for long periods of time.
Remove the battery from the device it powers. When working with any lead acid battery, wear safety goggles to protect your eyes. Depending on the piece of equipment, you may need a crescent wrench to detach the battery cables. If the battery has been in use and is hot, wait for it to cool before proceeding.
Prepare the battery for charging. Work in a well-ventilated space. Use baking soda and water to clean any deposits around the battery terminals (wear rubber gloves to avoid skin irritation). Remove the cell caps and fill the cells with distilled water if needed. Don't use tap water, which contains chemicals that can damage a battery.
Hook up the battery to the charger. Make sure the positive lead is on the positive terminal and negative to negative. Plug the charger into a regular (house current) socket. Follow the charger manufacturer's specifications to set voltage and current levels, then turn the charger on. Depending on how far the battery has discharged, you may need to charge it overnight.
Reinstall the battery or place it in maintenance mode. Once charging is complete, turn off the charger, remove the leads and replace the battery cell caps. If you are not going to use the battery immediately and you have a smart charger, you may leave it connected on maintenance (trickle charge) mode so it will be fully charged when you need it.
