How to disconnect car battery

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To disconnect a car battery, you should have the right tools and know the safe process. Disconnect the negative terminal of the battery. The car battery is now disconnected.

A rechargeable lead acid battery is a powerhouse for any car. It’s responsible for providing electrical current for every electrical appliance we use in cars. Sometimes there is a need to disconnect the car battery for good. So there should be safe procedures for this. 

This article is all about why to disconnect car batteries and how to disconnect car battery. Read the entire article to know the best and safest method how to disconnect a battery in a car.

Why to disconnect a car battery

There are four reasons why you should disconnect a car battery for good. 

  1. Car Maintenance and Repair
  2. Charging Car Battery
  3. Resetting Electronics or Clearing Fault Codes
  4. Storage or Long-Term Inactivity
  5. Security

Car Maintenance and Repair

It’s a good idea to disconnect a current battery during car maintenance and repair. Especially when you are working under the hood and near the battery. 

This is because of safety concerns. If you accidentally touch both positive and negative terminals of the battery at the same time you will get a serious electric shock.

Charging Car Battery

You might need to disconnect the car battery completely if you need to charge the car battery using battery charger. If you alternator fails to charge battery due to any reason. Then you have to charge is using an external car battery charger.

Resetting Electronics or Clearing Fault Codes

In most Modern cars disconnecting a car battery is one of the ways to reset the electronics and clear the faulty codes. Most modern cars have an engine control unit ECU that has a memory of its own.

The ECU Memory can be reset and all party codes can be removed just by disconnecting a car battery for a specific interval of time and then just reconnecting it back.

Storage or Long-Term Inactivity

It’s a good idea to discount a car battery if you are going to leave your car in the garage for a long time. This is also done for safety reasons. As any short circuit in vehicle electronics or on the battery terminal can cause Fire.


You can also disconnect a call battery to protect it from thieves. A car battery is responsible for starting the car and providing ignition voltage for the internal combustion engine. So a disconnected battery will help you save your car from thieves.

How to disconnect car battery 

On how to disconnect car battery, most people think they have to completely remove the car battery. You don’t have to completely remove the car battery from under the hood. just follow the following steps on how to disconnect a battery in a car. 

  1. Make sure your car is turned off (ignition turned off) and the car is parked on a flat surface
  2. First wear are the protective equipment like safety goggles and safety gloves
  3. You will need a ratchet wrench and an 8 mm 10 mm or 13 mm socket 
  4. Simply disconnect only the negative terminal of the battery
  5. Secure the negative terminal of the battery using any type of insulating material like a dry cloth
  6. That’s all your car battery is disconnected

Note:- Remember never try to touch both terminals of the battery at the same time. There is a separate automotive battery hazard class assign by US department of transportation for these car batteries, so always be careful. 

How long to leave battery disconnected to reset car computer

To reset the car computer you need to discount the car battery for at least 15 minutes. Try to press the horn or try to turn on the ignition. This will make the capacitor lose its charge thus draining any current remaining in the car electronics. 

This will make the car ECU lose its memory and switch back to the factory-set parameters. This is not a defined or preset time interval for your car ECU to reset. This time can be different for different car brands and different ECU make and model.

How to reset car computer without disconnecting battery

To reset the car computer without disconnecting the battery you need to remove the ECU fuse from the fuse box. The location of the fuse box and the ECU fuse is different for different car models. You may need to consult the user manual to find the fuse box.

In almost all modern cases there is a diagram on the inside of the fuse cover that locates the ECU fuse. Remove the fuse and keep it removed for about 15 to 20 minutes. Replace the fuse in its place and check the ECU for settings.

Remember your car ignition should be turned off before removing the fuse. You should be wearing the proper personal protective equipment like gloves to protect yourself from electric shock.


How do you disconnect a car battery to prevent drain?

If you are planning to watch your car in the garage for some time then it’s better to disconnect both negative and positive terminals of the battery. This will help you to prevent the rapid draining of your car battery.

What happens if you disconnect the positive terminal first?

If you disconnect the positive terminal of your car battery first. Then there are very good chances that you will get a serious electric shock. 

This is because by touching the positive terminal of the battery you will establish an electric circuit between you, the battery, and the ground you are standing on.

How long can you leave a car battery disconnected?

There is no specific time for which you can leave your car battery disconnected. You can leave it for as long as you wish to. 


How to disconnect car battery?  safely disconnecting only the negative terminal of the car battery will disconnect it. Always use proper tools and follow the safe and standard procedure to disconnect car batteries without hurting yourself or the battery and car.

If you still have any questions or want to add value to this article feel free to comment or contact us directly. Have a great day ahead.

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