How to disconnect a car battery: safe and easy steps - Car repairs - Driving and cycling

Make sure you safely disconnect your car battery with our time-tested, step-by-step guide.

From time to time, you might need to disconnect your car battery.

This could be for a variety of reasons, such as regularly inspecting your car battery.

Whether you’re cleaning the corrosion from a car battery, replacing the alternator, or replacing the whole battery, you need to know how to unhook a car battery safely.

Sometimes, when a battery is flat, it needs to be removed from the car in order to charge it back up.

If you won’t be using the car for an extended period, you should also disconnect the car battery so it doesn’t lose charge.

When dealing with electricity, you should always take extra precautions, and this is true when learning how to disconnect a car battery, too.

If you disconnect or reconnect a battery wrong, you could receive a nasty shock, and it even has the potential to damage the battery and onboard electrical devices.

Here, we’ll show you how to disconnect a car battery the right way and remove the battery from your vehicle safely.

When you need to disconnect a car battery, you should think about safety, first and foremost.

Even if you’ve discovered your car battery is dead, taking care is key.

Your vehicle should not be turned on, the handbrake should be applied, and it should be parked on level ground.

You’ll also need a few tools to disconnect the battery safely.

Checklist: tools and equipment

You should have the following tools to hand before you attempt to disconnect and remove a battery from a vehicle:

Wrench set
Pliers
Nitrile gloves
Cloth
Car battery wire brush
Car battery terminal puller (optional)
Hand towel (optional)

Once you have these tools to hand, you can get to work on disconnecting and removing the battery.

Let’s get started!

A auto technician disconnecting a car battery.

Whatever your reason for removing the car battery, follow these simple steps to learn how to unhook a car battery properly.

Step 1

Turn off the engine and remove the key from the ignition.

If you’ve been driving, wait 20 to 30 minutes for everything to cool down before you consider handling your car battery.

Locate your battery underneath the bonnet, it may have a plastic covering that you need to remove first to get access to it.

Identify which battery terminal is which.

The positive terminal is usually coded in red and has a plus symbol (+), while the negative terminal has a minus symbol (-) and will be coded black.

They may be covered with plastic caps which you need to remove or bend back before the next step.

Step 2

At this stage, make sure that your battery does not have any corrosion or damage.

If you see any cracking in the battery casing, liquid leaking out, or a bulge in the side of the battery, it’s best to hire a mechanic to remove it safely.

If there is rust or corrosion on the battery terminals and cables, take your battery brush and rub the terminals to remove the dry residue.

You can also give your battery a wipe with a cloth to remove any of the dirt or grime on it.

Step 3

Take your wrench and begin to unscrew the battery terminals, starting with the negative terminal first and then the positive terminal.

Loosen the nuts on the terminal post. If they’ve rusted or badly corroded then you might need to use the pliers to get a better grip of the nut.

The ideal tool to use on a very badly corroded terminal is a car battery terminal puller, which fits on top of the nut and slowly levers it off.

Remember: at no point should you let your metal wrench touch both the positive and negative terminals at the same time.

It’s not essential, but you can insulate the positive cable by wrapping the end of it in a hand towel until you need to reconnect the battery.

Step 4

On some cars there will also be a secure strap over the battery to hold it in place.

Take your wrench and unscrew the security hold, making sure that you don’t drop the nuts inside the vehicle as they’ll be difficult to retrieve.

The battery should now be free to remove from the car, so take it by the sides and pull it straight up.

A car battery weighs more than you might think, so remove it slowly and make sure you aren’t touching both of the terminals at the same time.

Place it on a flat surface away from any metal objects that might cause it to spark if they accidentally touch the terminals.

You can now properly clean the corroded battery terminals and wires if needed.

That’s all it takes!

And if you want to reconnect it again, place it back in the car and connect the wires the opposite way that you removed them, positive first, then negative.

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