How to Disconnect a Car Battery

Understanding how to disconnect a car battery is essential to your safety. Car batteries use a lead-acid storage system that combines lead plates in a sulfuric acid solution to generate more than 12 volts of electricity. Not something to be treated lightly.

How To Disconnect A Car Battery Safely

Safety first. Aside from the obvious danger of electrical shock, car batteries also pose a risk from the sulfuric acid they contain. Before starting to work on your car battery, make sure the vehicle is in a well-ventilated area and that you are wearing safety goggles and substantial rubber gloves.

Anatomy of a battery. You car battery is a large rectangular object made of heavy-duty plastic. Your battery has two poles projecting from the top: one for the positive charge and one for the negative. The positive pole will be marked in one of several ways: it may have "POS" stamped near it, it may have a "+" symbol stamped near it or the plastic around it may be colored red. The negative pole will also be marked with either "NEG" or a "-" symbol stamped near it. Your battery may also have several access caps that allow you to add water to the battery's cells.

Negativity. Always disconnect the negative battery cable first. With an appropriately sized box or adjustable wrench, loosen the bolt holding the negative cable's terminal clamp just until the clamp is loose enough to remove. Place the end of the cable where it will be out of the way and not touching any metal parts of the car.

Positively shocking! Next, remove the positive battery cable. With an appropriately sized box or adjustable wrench, loosen the bolt holding the positive cable's terminal clamp just until the clamp is loose enough to remove. Be careful not to touch the wrench against any metal object while it is touching the battery post or clamp. Place the end of the cable where it will be out of the way and not touching any metal parts of the car.

Cleaning up. If there is whitish-green powder around the cable clamps or battery posts, it can be removed using a solution of one cup of water mixed with two teaspoons of baking powder. This solution will cause the sulfate corrosion to fizz and loosen from the metal. Wipe corroded parts down and finish cleaning them with a wire brush.