Disconnecting a Negative Battery Terminal

man removing car battery
  • 1-2 hours
  • Intermediate
  • 0-100
What You'll Need
Safety goggles
Tool kit
What You'll Need
Safety goggles
Tool kit

It is critical to disconnect a negative battery terminal before starting any work on your car - any car manual or auto mechanic will tell you that. The negative battery terminal is your ground, which keeps you from getting shocked when working on the engines, the electrical, and the fuel parts of your car. Disconnecting this terminal is a safety precaution that will help keep you from feeling the full power that surges through your car. Put mildly, it’s the number one safety precaution you can take before starting work on your vehicle.

To disconnect this terminal, follow the easy steps below.

Step 1 - Turn Off the Car

Turn the key to the engine to 'Off'. Then, take the key out of the ignition. This may sound elementary, but it can be an overlooked step simply because it is so obvious.

Step 2 - Find the Battery

The battery is located under the hood, so open the hood and secure it with its stand. Most batteries are near the front of the engine. Sometimes they are at the side, and a few cars have batteries that are located under another engine piece. For these, you must maneuver around what is in your way.

Step 3 - Locate the Cable

Look for the black cable attached to the battery. There should be two cables, one black and one red. The red one is positive and should not be touched at this time. These cables attach to the battery with a spring clamp that is easily squeezed, opened, and removed or is clamped with a squeeze bolt, or even directly bolted to battery terminal.

Step 4 - Remove the Cable

While the cable is attached with a clamp to the battery, squeezing this clamp together may not be enough to easily remove it. You may have to wiggle the cable back and forth while squeezing until the clamp releases from the battery.

When the clamp does release from the battery, do not allow it to touch the battery. The electrical power in a car’s engine is activated by the battery. Contact between the negative battery terminal and the battery, even if the cable is not clamped onto the battery, may reactivate the electrical system within the car. This would negate all the reasons you have done this much work to ensure the cable is disconnected.

Hang the cable out of the way of the battery. The cable cord should be long enough to hang over the outside of the hood and down the side of the car. Usually the cables are about 1 foot or so in length. Secure the cable with a piece of tape to keep it in place while you perform whatever work you had planned.

Step 5 - Replace the Cable

When you are finished with the work on your vehicle, you will need to reattach the negative battery terminal to the battery. Reverse the removal process to reconnect the negative cable onto the battery at the location from which you removed it.

As always, when performing any work on your car, you should wear safety equipment such as safety goggles and gloves to help prevent injury. Disconnecting a negative battery terminal is an easy task, but you are working around a battery. Batteries contain acid and can cause injury if proper safety precautions are not taken.