How to Replace a Car Battery

Before starting the replacement process, it's crucial to ensure safety and prevent any damage to your vehicle’s electrical system by completely turning off the engine. This step is vital to avoid any accidental starting of the engine during the battery replacement process.

Next, engage the parking brake to keep your car stationary and prevent it from rolling while you work. This adds an extra layer of safety, especially if you're working on a slope or uneven surface.

Safety should always be your top priority when working on your car. Taking these simple precautions for nearly any repair, including turning off the engine and engaging the parking brake, can prevent accidents or mishaps.

Though it may seem obvious, the first step of any car battery replacement is always to locate the battery itself. Most batteries are located under the hood, but in some cases, your vehicle’s battery may be mounted in the trunk near the spare tire, or could be installed behind a wheel well and require the removal of a splash guard. Check your vehicle’s owners manual if you’re not sure where your battery is located. Then follow these helpful instructions to replace your vehicle’s battery yourself.

Identifying and understanding the posts and terminals on your battery is an important step in disconnecting it for replacement. A car battery has two posts and terminals – positive and negative . They are typically labeled with a plus and minus sign on the battery case. The positive post is usually connected using a battery terminal to a red battery cable, and the negative post is connected to a black battery cable.

Your battery may be a top post or side post battery, which simply refers to where the posts are located. Top post batteries typically use clamp terminals with a bolt and nut that squeeze the terminal together over the post for a tight connection. Side terminal batteries use bolts that pass through the terminal and into the battery post. Correctly identifying these terminals and the type of battery you have is crucial to the battery replacement and selection process.

A battery hold down is designed to keep the battery from moving while the vehicle is in operation. This may look like a strap with two J-hooks over the top of the battery, or could be a nylon strap or bracket around the battery case or near the bottom lip of the battery. In most cases, battery hold downs can be removed by loosening the nuts or bolts that hold them in place, then lifting them off of the battery to free it.

To ensure safety and prevent any accidental electrical discharge, the first step in replacing a car battery is to disconnect the terminals, starting with the negative terminal.

Using a wrench or socket wrench of the appropriate size, locate the negative terminal, which is usually marked with a minus sign or labeled 'NEG' on the battery. Loosen the terminal clamp or bolt by turning it counterclockwise. Be cautious not to touch any metal parts with the wrench to avoid creating a short circuit.

Once the terminal is loose, carefully lift it off the negative terminal. You may need to wiggle it a bit to free it from the battery post. Set the negative terminal aside in a safe place, ensuring it doesn't come into contact with any metal surfaces.

Next, you’ll use your wrench or socket and ratchet to disconnect the positive terminal, which is marked with a plus sign or labeled ‘POS’ on the battery case. Loosen the terminal by turning the bolt or nut counterclockwise, then lift the terminal off and move the cable to the side.

Now that the battery cables and hold down have been removed, you should be able to lift the old battery out of the battery tray. Car batteries can be heavy, so use both hands and lift with your legs to avoid strain or injury.

Place the old battery in a safe location and handle the old battery with care. It should be placed away from any flammable materials or sources of ignition. You can take the old battery to your local O’Reilly Auto Parts for free battery recycling, or you may need to use it as a core when purchasing your new battery.

With the old battery removed, you should be ready to install your new battery.

Carefully lower the new battery into the battery tray, ensuring it is properly seated and aligned with the hold-down clamp. Ensure the battery is fully settled into the tray before continuing to install.

Cleaning the battery terminals is an important step in replacing a car battery. Over time, corrosion can build up on the terminals, which can prevent a proper connection and affect your battery's performance. Use a battery terminal cleaning solvent and a battery brush to clean the protective coating from the battery posts and any corrosion from the battery terminals before reinstalling the battery terminals.

Once the terminals and posts are clean, you can install your battery terminal protectant washers. These washers contain neutralizing chemicals that help to prevent the chemical reaction that causes battery post corrosion. You can learn more about how to properly clean and protect battery terminals with our How-To video.

Start by connecting the positive terminal first. Place the terminal clamp over the positive post, marked with a plus sign or ‘POS’ on your battery case.Tighten the battery terminal with a wrench or socket until the terminal is snug against the battery post.

Repeat the process for the negative battery terminal, securing it to the post marked with a minus sign or ‘NEG’ on the battery case. Ensure both clamps are tight and secure.

To further inhibit corrosion, it’s a good idea to use terminal protective spray on the battery terminals and posts. Spray the terminals and posts thoroughly, and wipe off any excess spray.

Position the hold down, strap, or hooks appropriately against the battery and tray, and secure it using your wrench or socket.