Once you're sure your car's battery is completely dead and needs to be replaced, your next move will be to remove the current battery. Before you can tear it out of the engine bay, there are a few things to do first. Park your vehicle on a flat surface away from any open flames, as battery acid is corrosive and produces flammable gas. You should also wear gloves and protective eyewear during the process, to avoid getting any corrosive materials on your skin or near your eyes.
Even when the engine is off, a car battery may still produce an electrical charge as long as the terminals are connected, so it is best to err on the side of caution during this process. When using metal tools around the battery and the engine, take care to avoid touching them to metal surfaces, as this can set off an electrical spark.
Before you begin removing the battery, you should clean off any corrosion from around the terminals. Removing this buildup makes for safer removal and disposal. After this step, you will need to disconnect the battery terminals. Always start with the negative, or ground, wire. This wire is typically black in color, while the positive terminal cord will likely be either red or orange.
Use a wrench or pair of pliers to loosen the nut on the negative terminal. You may need to use another tool to clamp the bolt in place. Once it is loose enough, you will be able to remove the wire clamp from the bolt. Before you do this, be sure to place your tools on the ground or another surface away from the engine to prevent a spark. Follow the same steps for the positive terminal after the negative wire has been safely removed.
The next step after disconnecting the battery is to unfasten any parts holding it in place. This will likely require the use of a wrench or even a socket, depending on your particular vehicle. If your battery was leaking, there may be corrosion underneath it that could make it difficult to remove. Some batteries have handles to facilitate their removal from the battery tray, while others may need to be lifted from the base, as they are heavy.
After you remove the old battery, take the time to clean the tray and the terminal clamps before installing the new battery. If they are difficult to clean, you may want to think about replacing them as well.