How to Safely Disconnect Car Battery?

As you are running your vehicle, at some point the need may arise for you to disconnect the battery terminals. There could be so many reasons for it, ranging from fault troubleshooting, replacing a bad battery terminal, to full maintenance of the vehicle. Though it could appear difficult and stressful, the process is straightforward and can be achieved in a few minutes.

You need to apply caution when disconnecting the battery terminals to avoid terminal damage. Beyond holding electrical charges, batteries have corrosive materials that are inflammable. Disconnecting may require a couple of tools like a socket wrench. Therefore, take the following steps on how to safely disconnect car battery on your vehicle.

which battery terminal to disconnect when working on car

How to safely disconnect the car battery

Battery terminals are made of lead; it wears off when not properly connected or disconnected. Also, consider battery polarities because you don’t just take off any terminal. The procedures below show how to disconnect a car battery order.

Turn off the ignition & apply safety procedures.

How to safely disconnect car battery

Before you disconnect the battery from the engine, turn off the ignition key first and retrieve the key. Keep the door open, and it could lock up when the battery terminal is replaced, depending on the type of your car. Ensure that your car is in the park position; if you are using automatic transmission or if it’s a manual transmission, put it in the first gear selector.

It is recommended that you should apply some safety procedures when disconnecting battery terminals since the car battery stores electric charges. Also, the car battery is capable of releasing flammable gases. Therefore, it is strongly advised that you should keep a fire extinguisher in place and wear some safety gloves and eye protection equipment.

Open the hood and locate the battery.

how to disconnect car battery for storage

After you have turned off the ignition, the next action is to open the hood and pull the hood lever or press a button that is normally located below or beside the steering wheel. If you can’t locate your car hood level, then you have to refer to your car owner’s manual for guidance. Some car manufacturers sometimes have their batteries installed out of sight in the trunk. Therefore, if the battery is not in the hood, then it’s placed in your car’s trunk. Once you locate the battery, proceed to the next step.

Determine the size of wrench you need to loosen the terminal nut

how to remove a car battery

Take a visual inspection of your vehicle battery and the terminals. Ascertain visually the wrench size you’ll need to unbolt the nuts. You will be required to have a couple of wrenches to perform the job, based on the space available to maneuver the wrench.

A single wrench is enough to get the job done if the terminal uses a single bolt, but if it’s a bolt and nut, then you will need two wrenches. Most battery cable clamps have 10mm bolts. Therefore, you should use a 10mm flat wrench to disconnect the terminals. A set of socket-wrench with the same-size socket will serve the same purpose as well.

Disconnect the battery negative cable

disconnect car battery negative only

It is a good practice to always disconnect your negative battery terminal first to minimize the risk of sparks that can lead to car electronics damage and battery explosion. Once you have located the negative terminal, use the wrench to free the nut that tightens the terminal. Turn the wrench counterclockwise direction.

Once it is free, you can proceed with your hands if you know how to disconnect car batteries without tools, which entails gently wiggling off the cables. Remove the nut but ensure you put on gloves. If your vehicle uses a double battery, the same procedure applies, but you will have to disconnect the jumper cable after you have disconnected the negative terminal.

In any case, if you’re working on your car’s electrical system, you have to disconnect car battery negative only. There’s no need to disconnect both cables.

Disconnect the battery positive cable.

disconnect car battery positive cable

Once you have successfully disconnected the negative cable, the next is to disconnect the positive cable. Also, use the right wrench from your mechanic toolbox and turn the wrench counterclockwise to free the nuts. Avoid bridging the positive and negative terminal of the battery, as it could damage the battery or cause an explosion.

Ensure the positive terminal doesn’t come into contact with the car chassis. The car’s electrical circuit could get disturbed because there could be some residual charges left in the system. It could also lead to electronic damage.

Remove the battery strap and pull out the battery

how to remove car battery

Most car batteries are fastened and secured with a bracket or strap that ties the battery to the sitting. You need to unscrew the strap before you can pull out of the battery.

Unscrewing the battery will also require a sizeable wrench, possibly of a bigger diameter. Make up the spanner on the nut and turn counterclockwise. Pull the battery carefully so that both terminals don’t touch the metal body at the same time to avoid an electric spark.

Cleaning the battery terminals

Some disconnected battery terminals can be corroded over time due to moisture. Therefore, after you have disconnected your car battery terminal, inspect it. If the battery is later reconnected with a corroded terminal and you try to start the car, the engine may not start due to poor conductivity. Therefore, ensure that you clean battery corrosion on the terminals before reconnection.

To clean corrosion, scrub the terminals with a wire brush or sandpaper until there’s no grime or dust visible. After you have removed the corrosion, spray water on the cables and dry the water with a clean cloth or rag. Once the terminals are clean and dry, apply little grease to them to provide some lubrication and prevent corrosion in the future.


When should you need to disconnect the Batteries?

  • When parking a car for a long period
  • When replacing a battery
  • When cleaning or changing the battery terminal
  • If your car drains, the battery charges
  • For proper troubleshooting
  • When doing major work

Which battery terminal must be disconnected first and why?

Disconnecting the car battery from the engine is not a hard task. You only need to know the cable to disconnect first. If you properly review this article, you will learn how to disconnect car batteries for storage if you plan on parking your car for a long.

The negative cable of the battery should be disconnected first when removing the battery. The reason is that the negative cable from the battery is connected directly to the vehicle chassis. Therefore, you can short-circuit the battery if there is a contract between the positive cable and the car body.

Can you just disconnect the negative terminal?

You can disconnect the battery’s negative terminal. This is because the negative terminal is connected to the ground, and disconnecting it first reduces the possibility of short-circuiting the battery by removing the connection to ‘ground.’ Avoid the negative terminal to make contact with the positive one.

How do I temporarily disconnect my car battery?

Your car may develop a fault that could result in draining the battery charge each time the car is turned off and left for some hours or days. When you are faced with a challenge like this, a permanent disconnection could be time-consuming and stressful. The reason is that you pass through the process of disconnecting all battery terminals and pulling out the battery.

To ease the stress and conserve time, just disconnect the car battery and only the negative cable. The reason is that disconnecting the negative terminal breaks the entire car chassis from the circuit.

Why do you disconnect the negative first?

The negative terminal from the battery is connected directly to the vehicle chassis/ground and then to other components in the car. Therefore, disconnecting it first will isolate the car chassis from the negative polarity of the battery and reduce the chance of short-circuiting. It will also protect your battery and other car electronic devices.

What happens if you disconnect the positive terminal first?

Always disconnect the negative terminal first. If you try disconnecting the positive cable first, your spanner can slip and create a short circuit to the car chassis or a spark like an instantaneous arc weld. Knowing how to reconnect car battery terminals will Save you from a lot of stress and electrical issues that could result in catastrophic damage.

Which battery terminal gets connected first?

When reinstalling the cables to the battery, you have to connect the positive cable before the negative. If the negative terminal is connected first, the car’s body becomes charged together, with nuts and bolts on the body. If the spanner touches the frame or any grounded part of it when connecting the positive cable, it may cause a short circuit that could result in a battery explosion.

Should you disconnect the car battery when not in use?

If you are going on a vacation or you plan on taking a winter trip and are not in use for a while, there’s one thing that should not skip your mind. It is disconnecting your car battery. Disconnecting the car battery when on vacation could save you from replacing it when you return.

The car’s electrical systems, such as the headlights, can still run the battery down while the ignition is off. This means your car might not start due to a drained battery and may require you to jump-start your car.

Final Words:

It is very important to learn how to safely disconnect car batteries because of some situations where there is no auto mechanic available. It is key to understand your battery polarity and also to know which terminal to disconnect first when removing the battery. Also, it is recommended to maintain the battery regularly by cleaning battery corrosion.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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