How to disconnect a car battery: 5 steps

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How to disconnect a car battery: 5 steps
How to disconnect a car battery: 5 steps

Car batteries store a considerable amount of energy and are built to deliver an instant electric shock. They should be handled with care when you power your car to start it or when working on the electrical system. If you need to disconnect a car battery, follow the steps below.



Step 1. Take the necessary precautions before you try to disconnect your battery

In addition to containing a potentially lethal electrical charge, batteries have corrosive agents that emit a flammable gas. Before removing your car battery, follow the safety steps below.

  • Turn off the ignition.
  • Wear gloves and safety glasses to protect your eyes and hands.
Disconnect a Car Battery Step 2
Disconnect a Car Battery Step 2

Step 2. Find the negative terminal on top of your battery

It usually has a black cover. Perhaps the same battery has a negative symbol printed near its corresponding connection. Typically, the positive terminal has a red cover or positive symbol printed near its corresponding connection.


Step 3. Determine the size of the socket or wrench you need to loosen the nut on the negative terminal

Always work with the negative terminal before moving to the positive when disconnecting a battery.

  • Take a socket from your kit and hold it close, not in contact, to the nut on the negative terminal of your battery. Visually check the size of the socket you will need to loosen the nut.
  • Place the approximate size die on your ratchet. You may have to add an extension to the wrench to reach the nut.
  • Tuck the socket into the nut on the negative terminal and turn it counterclockwise. Remember, to the right it tightens and to the left it loosens. It will take a few turns to loosen the nut.
  • Pull out the negative battery connector when you have loosened the nut. Push it to the side so that it is not in contact with the battery while you work on it.
  • If the cable is seized in the battery port, you will need a special tool to remove the negative connector. Ask at local auto parts stores or a mechanic.
Disconnect a Car Battery Step 4
Disconnect a Car Battery Step 4

Step 4. Follow the same procedure to disconnect the positive terminal

After removing the positive connector from the terminal, do not let it touch any metal part of the carriage. There is still current left in the system which, if you touch a metal surface, could interrupt or damage the vehicle's circuits.


Step 5. Keep working

Now that your battery cables are disconnected, you can perform repairs on the vehicle's electrical components. If you need to replace your battery with a new one, do it in a few steps.

  • After you have disconnected your battery, unscrew the brackets that keep it fixed in its tray.
  • Lift the battery out of its tray. Keep in mind that a car battery weighs approximately 40 pounds (18 kg), so ask for help if you need it.
  • Use an old toothbrush to brush the battery tray and cables with a diluted baking soda mixture. Let them dry before connecting them to your new battery.
  • Place the new battery on the tray and tighten the clamps.
  • Connect the wire from the positive terminal first, then the negative terminal. Remember to tighten all the nuts carefully.
  • Close the hood and start the car.
  • Dispose of the old battery carefully. The auto parts store where you bought your new battery will likely accept the old one as part of a service agreement. If they don't, take it to a recycling center or auto shop. Most accept old batteries for a nominal fee.


  • Regular car batteries draw several hundred amperes, which is roughly the amount of current an electric arc welding uses. Don't try to test your battery's charge by touching the positive and negative terminals with a metal tool. The current is so high that it could damage the tool and injure you.
  • Use zip ties to keep the battery cables away to prevent them from coming into contact and causing a spark or electric shock.
  • Take off all jewelry, particularly rings and necklaces.
  • Work outside where fumes don't collect.
  • Wear eye protection and insulating gloves.
  • Hybrid vehicle batteries generate more than 300 volts, which is a potentially lethal amount. If you need to work on an electrical component in a hybrid vehicle, first disable the high-voltage battery in the back of the car. The connections are usually color-coded orange. Wear insulating gloves and tools when doing this to reduce the risk of shock. Make sure to follow the same procedure as the manufacturer for disconnecting a hybrid battery, as there must be additional steps to follow.

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