Disconnecting a car battery: The Whys and Hows

Updated Mar 04, 2021 | Same topic: Automotive FYIs

Learning these steps might save you time and money. 

For many of you who are experienced car owners, there’s a good chance that you can disconnect a car battery properly and without any issues. However, removing a car battery might be challenging for some especially for those who are new to cars.

How to Disconnect a Car Battery

So, to aid newer car owners, we’ll be talking about the proper way to disconnect a car battery, why you need to know how to, and what might happen if it isn’t done correctly. 

A picture of a man staring at his car's engine bay

New to cars? Then you must learn how to disconnect the battery 

A step-by-step guide to disconnecting a car battery safely 

Here are the steps to disconnect and remove a car battery properly and safely. Before trying these steps out on your own car, we recommend preparing the right tools for the job. You’ll need a 10mm wrench that can either be a socket or an open-type one. Why 10mm? That’s because most battery cables use a 10mm nut.

You might also need a pair of mechanic’s gloves especially if the battery is old/damaged and puking its acidic contents. You also need to be careful with corroded battery terminals and battery cable clamps. 

A picture of a car battery with a clamp

A car battery with a bracket

If you can’t find your car’s battery, please refer to your owner’s manual. 

Without further ado, here are the steps to disconnect and remove a car battery safely.

  1. Make sure that the car’s ignition is turned off, and the handbrake is applied. After that, open the car’s hood.
  2. Unscrew the negative cable clamp from the negative terminal first. This is the one with the “minus” sign.
  3. Unscrew the positive cable clamp from the positive terminal. This is the one with the “plus” sign. As you’re doing these, make sure that the wrench you’re using won’t come in contact with any metallic parts inside the engine bay.
  4. On most modern cars, car batteries have a fastener to keep them in place. Some of these need to be unscrewed, while some use a latch-type mechanism.
  5. Lift the battery out of the engine bay. Do note that car batteries are heavy so hold them properly.
  6. To reattach the battery, just apply the reverse. Connect the positive side first, then the negative side. Of note, make sure that the battery positive and negative sides match the cables before lifting the heavy battery into place.

>>> Related: Car battery in the Philippines: How long it lasts, what are the different types, and what to buy

Why we need to know how to disconnect and remove a car battery 

Knowing how to properly disconnect and/or remove a battery is useful because eventually, that battery will go bad. Sure, most car batteries nowadays can last up to four or even six years, but when it happens, replacing the battery yourself will save you a lot of time and money. 

Second, a battery that’s connected to a car that is not in use can slowly drain. This is more apparent when you’re off somewhere else for long periods of time, and not using the car. For example, when you’re out on vacation.   

A picture of a person unscrewing a battery clamp

Also, working on your own car is very satisfying

>>> Related: Everything you need to know about car battery prices in the Philippines

To prevent battery drain, you should disconnect the negative battery cable from its terminal. And just to be sure, zip ties the negative cable to a safe spot where it won’t touch any metallic parts of the car.  

Disconnecting a car battery is also useful when you’re prepping a car for long-term storage. Like if you’re shipping the car on long distances. 

Do note that disconnecting a car battery will reset your car’s electronics. Your car’s onboard clock will reset, so will the body control module, the climate control module, among others.  

What happens when you improperly disconnect a car battery? 

Imagine this scenario: You disconnected the positive cable first and you are now unscrewing the bolt on the positive terminal. Accidentally, your wrench has touched a metal piece of your car’s engine bay. The instant that happens, sparks suddenly fly out of the contact point.

This noisy, spectacular, and often dangerous occurrence is called a short. And yes, simply removing the negative side first will eliminate this possible scenario from happening.  

A picture of car battery terminals

Some car battery terminals nowadays do have protective rubber coverings to prevent accidental shorts

For more useful car maintenance guides like this, keep reading here on Philkotse.com.

Disconnecting a car battery: FAQs

1. Why do car batteries drain by themselves?

Answer: Sometimes, the reason why your car batteries drain on their own is a fault in the car’s electrical system.

2. How tight should the bolts be on the car battery cable clamp?

Answer: Tightening the car battery’s cable bolts too much can distort the terminal. This might result in a leak. As such, screw the bolt on just right and just snug enough that it won’t fall off.

3. How heavy is a typical car battery?

Answer: A typical car battery can weigh from 14 kg to 22 kg. Larger vehicles like trucks will use larger batteries that will weigh more.

4. What do I do if battery acid gets on my skin?

Answer: If battery acid gets on your skin, rinse the area with lukewarm water for around 20 minutes. If you’re wearing something in the affected area like a ring or watch, remove those. If blisters, irritation, and pain start to appear, it might be ideal to seek medical attention.

5. How long do car batteries last?

Answer: A car battery can last from four to six years.

Cesar G.B. Miguel

Cesar G.B. Miguel


Cesar Guiderone B. Miguel was born and raised in Iligan City, Lanao Del Norte. He graduated in 2010 with a Bachelor of Arts in English degree from Mindanao State University - Iligan Institute of Technology. He previously worked as a freelance writer for various websites, as a member of the Iligan City Disaster Risk Reduction Management's training staff, and as a medical sales representative.

Facebook: https://www.facebook.com/goridus.goridus

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