Sealed lead-acid batteries or maintenance-free batteries often have the letters "MF" printed on the housing. Traditional lead-acid batteries have vent caps over each cell, allowing the escape of hydrogen gas and the addition of electrolyte to replace that lost in producing hydrogen. Sealed batteries may have the vent caps, but under normal use, they never require removal. While sealed batteries prevent a loss of electrolyte under normal conditions, they are still vulnerable to other forms of degradation. By regularly following a battery maintenance routine, you can extend its life and enhance its performance.

General Maintenance
Disconnect both battery leads, starting with the negative (-) lead. They are usually attached by battery clamps that require a wrench or large screwdriver to loosen them. Never apply excessive force or twist the clamps violently, as this may damage or snap the terminals. Place both leads out of the way.

Wipe the battery case with a dry cloth, removing all dirt, moisture and debris. Clean the metal terminals with a wire brush until they shine. Work on one terminal at a time, and never touch both simultaneously. Pay the same attention to the metal clamps on the battery leads, brushing them until the metal shines. Smear a thin layer of corrosion-inhibiting petroleum jelly on the terminals before reconnecting them.

Wipe away all loose debris, dirt, corrosion flakes and moisture with a soft, dry cloth. Examine the battery casing for damage. Dents, cracks and loose terminals indicate physical damage caused by movement of either the battery or something near it. Investigate and fix the problem.

Charging and Discharging the Battery
Establish the amp-hour rating of the battery. Find this on the battery case or in the battery manufacturer's data sheet. The amp-hour value states the theoretical amount of amperage the battery can provide, per hour, over a 20-hour period. Knowing this value when recharging the battery can extend its life.

Use a good-quality battery charger that allows you to set the charging current. Follow the manufacturer's recommended rate of charging. Do not charge at a higher rate, as it will generate excessive heat in the battery and may cause the electrolyte to boil.

Avoid fully discharging the battery. Lead-acid batteries should lose a small percentage of their capacity and then be recharged. Letting the battery discharge until it is very flat will dramatically reduce the life span of the battery.

Short Circuits
Disconnect the battery charger before undertaking any maintenance or modifications to associated wiring. Many vehicles save on wiring by using the metal chassis as the negative side of the circuit.

Maintain the associated wiring and ensure that connections are secure and free from corrosion. Loose and corroded connections create electrical resistance, draining the battery and reducing its power output. Loose and corroded wires may also come off their terminals, touch the opposite side of the circuit and short-circuit the battery.

Do not use metal tools if they may make contact across the battery terminals. Metal wrenches used to undo the terminal clips are a particular danger. Directly connecting the positive and negative sides of a lead-acid battery in this way causes a high current to flow between them, melting the wiring and producing extreme heat within the battery. It may also weld the tool across the terminals, and melt the flesh of your hand.