How To Disconnect A Car Battery

This is one of the simplest jobs out there, but there are a few steps to be mindful of before you start wrenching.

byTony Markovich|
car battery, decorated
Andrew P. Collins
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Automotive maintenance is primarily about 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. When it comes to disconnecting a car battery, it's a straightforward process usually involving a wrench or two and a few minutes of your time.

Removing a battery is perfectly safe and easy if you know what you're doing. However, there are risks involved, and you can create a big flaming mess if you're not careful. 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. Don't worry, though. Done right, this is an easy job that should only take you about 10 minutes.

You won't need much equipment for this job, either. Along with your new battery, a pair of safety glasses and mechanic gloves are good to keep your hands and eyes protected. You'll also want basic hand tools like screwdrivers and wrenches to enable you to access the battery and remove it from the vehicle. You may also want some cleaning supplies, like a wire brush and some baking soda and water on hand. Read on for the step-by-step instructions.

Many batteries have brackets or casings that need to be removed. Depositphotos

How To Disconnect A Car Battery, Step by Step

The first thing worth noting is that it's easier to do this job when the car is cold. There will be less heat coming from under the hood, and less hot parts to burn yourself on. It's best to start with you car parked in a flat shaded area where you have room to work on it safely without interruption.

Step 1: Find the battery

This sounds straightforward, but to change your battery, you first have to know where it is! Most cars keep the battery under the hood, normally off to one side of the engine bay. However, if you're looking under the hood and can't find it, that's okay. Just open up your owner's manual to find the battery location in your car. Some manufacturers, particularly European ones, like to put the battery in the trunk, or even under the rear seats in some cases. You might find your battery is lurking beneath some kind of cover or hidden access panel.

Step 2: Remove the terminals

Now, it's time to disconnect the battery from the car, electrically speaking. Start by loosening the bolt on the negative terminal of the battery. It's the one with the "-" minus symbol. Lift it away and place it somewhere away from the battery where it won't flop around. While doing so, be sure not to let any metal tools bridge the battery terminals, as this can lead to a dangerous short circuit. Once the negative terminal has been removed, do the same with the positive terminal. Now, your battery should be free from any connecting wires. If there is a small hose attached to a vent port on the battery, now is a good time to remove it as well.

Step 3: Remove the restraints

Your battery will be held in place with a mechanical restraint to stop it from bouncing around while the vehicle is in motion. Loosen the bolts on the battery hold-down bracket and remove it from the vehicle carefully. Be sure not to let the metal bracket touch across the battery terminals as you remove it, as this can lead to a dangerous short circuit.

Step 4: Remove the battery

With the terminals and the hold-down bracket removed, you should now be free to remove the battery from the car. Some batteries come with helpful handles, while others are best supported from the bottom while lifting. Keep the battery upright while lifting, as it is full of acid which you don't want to leak out. Plan your lift so you have room to move and somewhere to put the battery once it's out. While you're lifting, be careful not to touch the terminals on any metal part of the car. You may want to cover them with electrical tape if you're working in a tight compartment.

Step 5: (Optional) Clean the terminals

Look at the car's battery terminals. You may notice crusty white or green deposits or other signs of corrosion. These are best cleaned off 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. It's worth noting that a poor connection at the battery terminals can mimic many of the symptoms of a bad battery.

Step 6: (Optional) Install the new battery

If you're installing a new battery, simply follow the steps in reverse order. First put the new battery into place in the battery box, and then install the hold-down clamp to keep it in place. Then, install the terminals, positive first, then negative. Make sure to get the polarity correct, and tighten the terminals properly.

Final Tips For Disconnecting Your Car's Battery

If you don't want to lose your car's radio presets, clock setting, and so on, it can be worth investing in an OBD memory saver. This is a device that plugs in to the car and keeps 12-volt power to the car's electrical systems while you're changing the battery. Consult your owner's manual to determine whether this, or any other special procedures, are necessary while disconnecting or changing your car's battery.

Often, your old dead battery can be returned to a shop or recycling center. Speak to your local government about disposing of old lead acid car batteries, which cannot be thrown out in your regular household garbage pickup.

It's also worth inspecting your battery regularly as part of routine maintenance. Maintainable batteries need their water levels checked from time to time, and should be refilled with the appropriate distilled or deionized water for this use. Keeping the battery terminals clean is key as well. Loose or dirty battery terminals create a high resistance connection between the battery and the car and can mimic the symptoms of a dead battery. Meanwhile, if you're looking for more information about batteries and their lifespans, we can help there too.

Do not place any metal tools such as wrenches across the top of the battery. Bridging the two terminal posts on the battery can create a dangerous short circuit leading to fire or battery explosion. Depositphotos

Got a question? Got a pro tip? Send us a note: guidesandgear@thedrive.com

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