Do I Need to Disconnect Both Battery Terminals?

Replacing a car battery is essential, and it’s always best to disconnect both battery terminals to avoid any potential problems in its electrical system. If you don’t take this precaution, the new battery could have a discharged or faulty cell and will drain quickly. This blog post covers what happens if one of your terminals is disconnected, why it’s crucial to disconnect both, and how to disconnect your car’s battery without causing any problems.

How to disconnect a car battery for storage?

Disconnecting battery terminals is easy by unscrewing or unclipping them from the battery. If you plan on storing the vehicle for a short period (less than 90 days) and it is in an area with minimal temperature fluctuations, disconnecting one battery terminal should be sufficient.

Meanwhile, disconnecting both battery terminals is recommended if there will be significant temperature changes or if you plan to store the car for a longer time.

Consulting your car’s manual before disconnecting your battery would also be a good idea. Most manuals have specific instructions on how to store your car or truck properly.

What happens if you only disconnect the positive terminal first?

If you only disconnect the positive terminal, the battery will still discharge through the negative terminal, but disconnecting them in a different sequence won’t affect your battery life; however, it may cause an unnecessary voltage drop across the terminals which can lead to damaged equipment and reduced battery performance. Thus, it’s always best to disconnect both terminals to avoid any issues.

Which battery terminal to disconnect when working on car?

First, let’s look at why cars have two battery terminals. The battery’s negative terminal is installed directly on the engine block or structure. While the positive connection is made to the starter motor, removing the battery cable from the starter is recommended before doing any work on the car battery. This way, it can be grounded for safety purposes, allowing any potentially dangerous electrical currents to flow between these components easily.

The negative terminal should always be disconnected first since it’s connected to the ground. If you disconnect the positive connection first, there will still be a dangerous path for the current to flow, and it could easily cause an electrical shock.

If you’re unsure how to disconnect a car battery, it’s always best to take it to a mechanic or consult your car’s manual. Also, many online tutorials will help you show how to do it safely.

Do I need to disconnect both battery terminals when charging?

It depends on your car’s specific battery and charging system. But in general, you should probably disconnect both battery terminals when charging – unless you know that your battery and charging system doesn’t require it. Remember that disconnecting both battery terminals helps to avoid damaging your car’s electrical system while the battery is being charged.

Do I disconnect the positive or negative?

It depends on what you’re trying to do. If you’re trying to disable the battery, it doesn’t matter which one you disconnect first. However, if you disconnect battery terminal, you should disconnect the negative terminal first, followed by the positive terminal.

If you disconnect ground or positive first, it could create a spark between the terminal and the chassis (since they’ll be at different electrical potentials). Additionally, some batteries have a vent on the side or top of them, and if this is obstructed when trying to remove the battery, it could cause an explosion. So, to be safe, always disconnect the negative terminal first and then the positive terminal.


Disconnecting one battery terminal is only possible if you plan on storing the vehicle for less than 90 days. If not, it’s crucial to disconnect both battery terminals to prevent short circuits that damage sensitive components in your car’s electrical system while charging it. Always take extra precautions when disconnecting battery terminals and ensure that both of the battery’s posts are clean and free of corrosion before reconnecting them. Lastly, wear safety glasses and gloves as the acid from a car battery is very dangerous.

About the author, Phil Borges

Phil Borges is a battery aficionado. He's written extensively about batteries, and he loves nothing more than discussing the latest innovations in the industry. He has a deep understanding of how batteries work, and he's always on the lookout for new ways to improve their performance.