Car batteries are not invincible. In fact, car batteries can die for any number of reasons: corrosion, intense heat or cold, age, a short circuit or headlights accidentally left burning. If you have a dead car battery, reviving it is a fairly simple process. For a complete revival, however, you need to set aside several hours for the battery charger to do its work. Once it has been sufficiently charged, your car battery should be like new again.
Clean the case of the battery with an old rag or cloth. If the battery is caked in dirt or grease, it will be more prone to gather moisture and discharge at a faster rate.
Clean the posts using a battery post and terminal cleaning tool. Brush the posts until they’re clean. Also brush the terminals on the car to ensure they’re clean as well. If you don’t own a cleaning tool, a wire brush will suffice.
Check the electrolyte levels in your car battery. Simply pry the caps off the top of the battery and look inside. If the cells are dry, replenish them with distilled water. Add enough water so that the bottom of the vent walls inside the battery are covered. If you own a maintenance-free car battery, you will not be able to add water because the battery is sealed.
Ensure that your battery charger is unplugged and turned off. Then connect the positive, red clip to the positive ( + ) battery post. If you still have the battery connected to the car, you should connect the negative, black clip of the charger to an unpainted solid metal piece, such as a bolt or bracket, within the engine compartment. If you’ve removed the battery, go ahead and connect the negative clip to the negative post on the car battery.
Set your charger to the proper voltage and desired amperage. The voltage should be set at 12 volts for a car battery. For a dead battery, you’ll want to set your amperage fairly low in order to slow-charge the battery. A setting of 2 to 4 amps should be sufficient. If your car battery charger does not have variable settings for voltage and amperage, don’t worry. Simply proceed to Step 3.
Turn your battery charger to the “On” position and plug its cord into a nearby electrical socket.
Wait. For a dead battery that must be completely revived, you might need to allow several hours for a complete charge. Check in on the battery throughout the charging period. Your charger should have an indicator light or gauge which tells you when the battery has a full charge. If you have an automatic charger, it should turn off by itself once the battery has been fully charged.
Unplug your car battery charger once the battery has been fully charged. Turn off the power switch and disconnect the clips, starting with the negative clip first. Your car battery should be fully revived.