Textual description of firstImageUrl

How to Disconnect a Car Battery

Free Car Diagnostic Image

How do you disconnect a car battery safely? Which battery cable should be removed first? Let's say you need to clean or replace your car's battery or disconnect a car battery to reset the computer, so you disconnect the battery. Here's what you do to disconnect the car battery safely.

The battery will discharge its energy if more energy is used than that supplied by the alternator, or if too much electricity is used while the engine is stopped. With use, the amount of battery electrolyte gradually diminishes because the battery is charged and discharged and due to evaporation. Electrolyte diminishes hastily, mainly while the battery is overcharged and at some point in the summer season. If the stored energy in a battery decreases, it will become tough to start the engine then you need to disconnect the battery to replace it.

How to Disconnect A Car Battery

1. Park the car in a safe place. First is to park the car in a safe place then turn OFF the engine, make sure that the car is a park on level ground and the parking brake is engaged, and use a tire stopper for safety purposes of shift the gear into reverse gear if there is no parking brake or tire stopper.

It is very important to turn off the engine before disconnecting the battery because the battery contains electrical charge and flammable gas produced by corrosive agents, this is done to avoid the possibility of a fire accident.

2. Locate battery negative terminal. Now, Locate the battery negative terminal. Usually, it contains a black plastic indicator label or a negative symbol embedded on the battery casing, however, if you cannot find both locate the word “NEG” on the battery case near the terminal. The terminal with a red plastic label is the positive or with a positive sign embedded on the battery casing located near the terminal, sometimes the word “POS” is printed on the casing near the battery pole.

Free Car Diagnostic Images

3. Check the type of tools to use. Once the negative terminal is located, check the type of tools to be used for loosening the terminal nut. Usually, an open wrench or socket with a size 10 mm is used to loosen the terminal nut.

Free Car Diagnostic

Disconnect the negative terminal first, this is to prevent a short circuit when the tools you use touches the body of the vehicle.

Free Car Diagnostic Image

If you disconnect the positive terminal first, there is a possibility that the tool touches the vehicle body and short-circuited the system.

4. Disconnect the negative terminal. Start disconnecting the cable on the negative terminal. Remember that it is not necessary to remove the nut on the terminal you just need to loosen the nut of the battery cable to disconnect the terminal.

5. Disconnect the positive terminal. After the negative terminal was disconnected, proceed with the disconnection of the positive terminal.

6. Loosen battery fix or clamp.

Now loosen the battery clamp to completely remove the car battery.

Disconnecting a car battery can become dangerous if not done correctly that is why it is important to know how to disconnect a car battery safely so that you may avoid an accident when you want to replace your car battery.

When replacing the battery, ensure that the battery is mounted correctly, with the side of the terminal facing the right side of the vehicle. Be sure that the battery tray and the pressing board are correctly fixed to prevent the battery from moving in the event of an accident or emergency braking.

The disconnecting car battery will be applicable when replacing a battery and when you are about to work on any electrical parts of your car. When returning the battery do the sequence in the reverse position which means that the positive terminal must be connected first before the negative terminal is connected.

Only use a battery of the same model and the same specification as that of the battery to be replaced. Otherwise, there may be some situations where the battery is of inconsistent dimensions or different terminal positions, thus it is likely to cause battery damage, leakage, or fire.

How to Install a Car Battery
How to install a car battery is something that every car owner should know. First, boost charge the batteries for top efficiency before installation. Read more » How to Install a Car Battery

Watch more videos on auto repair. Subscribe to our Cartechhome Channel on Youtube.
Help us expand the people we help by sharing this information with others. Thank you !!!


  1. should I disconnect the battery when the car is being left idle for three months or more?

    1. Disconnecting the battery will only prolong its discharging than when it is connected to the car and is not a guarantee that it can still be use after three months. Battery will self discharge even when not connected to the car and usually it will only takes about 45 days approximately to self discharge. So, even when the battery is not connected and left it for three months the battery charge will be gone. My advise is to left it connected to the car and have someone start the car for at least every week to let it charge.


Share with us what you think about this topic to help others know more information that this article did not cover.
Kung may tanong po kayo comment lang po, at sasagutin namin sa mga susunod na araw. Marami pong salamat!

Free Car Diagnostic