How To Disconnect A Car Battery
You don't want to shock yourself.
- Auto Repair and Maintenance
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Automotive maintenance is primarily based upon the art of taking things apart and putting them back together. Sometimes that involves nuts and bolts, sometimes it involves gaskets, and other times it involves wires and cables. In the case of a car battery, it is connected to the charging system with two heavy-duty cables attached to two top-mounted posts known as terminals.
To remove a battery, you must remove the cables from the terminals. Those terminals are labeled with a plus symbol (+) and red indicators on the positive terminal and a minus symbol (-) with black indicators. Crossing wires or removing the wrong cable first could lead to sparking or other harmful dangers, such as ripping a hole in the spacetime continuum, so you need to know what you’re doing before you start taking things off.
To prevent dangerous situations, you need to understand how to properly handle a car battery, which is hot with voltage and traditionally filled with free-flowing acid—yikes. The Drive has put together a step-by-step guide for how to disconnect a car battery. Follow along below.
Car Battery Basics
Estimated Time Needed: 10 minutes
Skill Level: Beginner
Vehicle System: Charging
Car Battery Safety
Working on your car can be dangerous and messy, so here’s exactly what you’ll need to ensure you leave the garage in the same condition you entered.
Everything You’ll Need To Disconnect A Car Battery
We’re not psychic, nor are we snooping through your toolbox or garage, so here’s exactly what you’ll need to get the job done.
- Wrench or socket set
- Wire brush, if necessary
- Baking soda and water cleaning solution, if necessary
Organizing your tools and gear so everything is easily reachable will save precious minutes waiting for your handy-dandy child or four-legged helper to bring you the sandpaper or blowtorch. (You won't need a blowtorch for this job. Please don’t have your kid hand you a blowtorch—Ed.)
You’ll also need a flat workspace, such as a garage floor, driveway, or street parking. Check your local laws to make sure you’re not violating any codes when using the street because we aren’t getting your ride out of the clink.
How To Disconnect A Car Battery
Let’s do this!
- Park the car, shut it off, let it cool down, and pop the hood. The latch is typically located on the driver’s side underneath the dashboard or around that area.
- Loosen the bolt on the negative terminal (the one with the “-” minus symbol), lift it off the terminal, and place it away from the battery where it is not touching metal.
- Loosen the bolt on the positive terminal (the one with the “+” plus symbol), lift it off the terminal, and place it away from the battery where it is not touching metal.
- Loosen any bolts on the battery hold-down bracket and remove the bracket.
- Lifting from the bottom (it’s heavy!), remove the battery.
- If the battery was corroded, clean the cables and battery seat with a wire brush and a solution of baking soda and water. For more information read The Drive’s garage guide for How To Clean Battery Terminals.
Symptoms of a Bad Battery
It’s easy to tell if your battery is bad. Simply look for these symptoms:
- Dim or inconsistent headlights
- Dim interior lights
- Interior lights turn on but the car won’t start
- Literally nothing on the car works
For more information on battery problems, read The Drive’s guide, Why is Your Battery Light On and What Does It Mean?
How To Test a Battery
There are a couple ways to test a battery.
- Execute the test with a made-for-the-job car battery tester. This device gives you the ability to test the battery under load.
- Test the battery voltage with a multimeter. A fully charged battery should register 12.6 volts or more. If the numbers do not match up, try recharging the battery with a trickle charger before replacing it.
For more information about batteries and their lifespans, read The Drive’s informational article, How Long Does a Car Battery Last?
You have the questions, The Drive has the answers!
Q. What Is an OBD ECU Memory Saver?
A. On certain modern cars, the ECU stores information that is required to run the car correctly. Things like idle speed and other settings are kept as memories that the car can reference. If you unplug the battery, you might lose all of those settings, and the car will be confused once you start it back up.
A cheap tool known as OBD ECU memory saver plugs into your OBD port and will maintain power so those settings are not lost. Check your owner’s manual or contact your dealership to determine if this is necessary on your ride.
Q. Which Terminal Do You Take Off First?
A. The negative terminal.
Q. Can I Just Disconnect the Negative Terminal?
A. Whatever the reason, if you’re disconnecting one terminal, you should do both. Then make sure the cables and battery are out of the way to prevent any sparking.
Q. How Long Can a Car Sit Without Being Driven?
A. It’s never a good idea to let a car sit unused and unloved. Literally dozens of issues such as damaged tires, could pop up as a result of sitting too long, so it’s best to occasionally start the car and move it even a few feet, at the bare minimum.
Get Help With Disconnecting A Car Battery From a Mechanic On JustAnswer
Although The Drive’s detailed how-to guides are easy to follow, a rusty bolt, an engine component not in the correct position, or a messy oil leak can derail a project. That’s why we’ve partnered with JustAnswer, which connects you to certified mechanics around the globe, to get you through even the toughest jobs.
So if you’re stuck or have a question, click here and to talk to a mechanic near you.
Got a question? Got a pro tip? Send us a note: email@example.com
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