Which Car Battery Terminal Is Positive And Negative?

Knowing which terminal is positive, then you will know the right way to connect the battery.

If you own and drive a car and you don’t know yet which car battery terminal is positive and which is negative, you better know now. There will always come a time in the life of your battery when you will have to disconnect it for one reason or the other, If you are clueless as to which terminal is positive and which one is negative, you will be in trouble.

How can you recognize a positive car battery terminal? The positive terminal is the one with, usually, a red cap and red cables attached to it and with a + sign beside the cap. The negative terminal is normally distinguished by its black cap and black cables and the – minus sign beside it.

What Your Car Battery Is Made Of?

Majority of car batteries being used today are lead-acid rechargeable batteries. These batteries are made up of cells connected in a series. Each cell contains a lead plate called an anode and a cathode, a lead oxide plate. These cells are submerged in a liquid substance called electrolyte which is a mixture of water and sulfuric acid and isolated from each other by a separator.

The electricity that is supplied by the battery to start a car is created by a chemical reaction between the electrolyte and the plates. When you start the engine of the car, the battery is being discharged, A chemical reaction between the electrolyte and the plates occur changing the surface of the plates to lead sulfate.

Once the engine is already running, the alternator takes over in supplying the electrical requirement of the car and at the same time, it recharges the battery. While the battery is being charged the chemical reaction is reversed.

The battery terminals are the two lead posts usually found on top of the battery. They are the contacts that receive a load or charge. It is through the terminals also that power is delivered to the engine and the other electrical accessories when the demand for electricity is more than what the alternator can handle.

Why Is It Important To Distinguish The Positive From the Negative Terminal?

As we know, there is a positive and a negative battery terminal. It is worth repeating at this point that the positive terminal is distinguished by the + sign beside the positive terminal cap. The cap and the cable attached to it are usually colored red. On the other hand, the negative terminal has a – sign beside its cap and the cap and cables are black.

This knowledge is important when disconnecting and connecting a car battery. The negative terminal of a battery is connected to the chassis of the car and as a consequence, it is grounded. That is why the negative terminal is called the “ground” terminal.

When disconnecting a battery, the negative terminal is disconnected first to cut off the circuit and avoid a short. If you disconnect the negative terminal first, and you accidentally hit the chassis of the car with a wrench there will be no electricity flow and no shorting can occur. The ground terminal is already grounded and the electricity has no return route to the negative terminal.

When connecting the battery, the positive terminal is connected first and the ground terminal last for this very same reason.

Why Do You Have To Disconnect A Car Battery?

As I’ve said, at one point in the life of your battery you will need to disconnect it. It could be for any of these reasons:

● You are going away on vacation and you are leaving your car in storage

If you don’t disconnect your battery before you leave for an extended vacation you might need to buy a new battery when you get home. Some of the electronic accessories of your car such as the clock and the onboard computer continue to draw power from your battery even if it is in park mode. This draw on your battery is called a parasitic draw.

A parasitic draw can drain your battery if you leave your car sitting for a long time, so much so that it might refuse to start when you get back. Then, you will need to buy a new one to replace it, an unnecessary expense that can be avoided had you been more mindful.

● When you will jump-start the car battery

When your battery dies on you because it has been discharged, you may be able to bring it back to life, at least momentarily, by jump-starting it. You jump-start a flat battery using a healthy battery of another car or with a portable jump starter.

If you jump-start your car too often, like three times in a month, you will be better off replacing it with a new one. You see, when you jump-start a battery, some of the electronic system in the car could get damaged. This is particularly true for many of the recent car models.

● When you have to replace the battery

A battery is given a normal lifespan of three to five years, although some claim their batteries have served them for more than that. On the other hand, some car owners experience some signs of a failing battery even before it completes its third year. This is usually the case of batteries that are overcharged or undercharged.

But, in general, even batteries that are well-maintained will already be showing some signs of ageing after the third year. You see, every time you charge your car battery, it loses some of its capacity to hold a charge. And, the time will come when you will already experience a car that won’t start especially in the dead of winter. Then, you will need to replace it. (Here is how).

Other reasons why you might need to replace your car battery with a new one is when it is leaking acid or when it is damaged beyond repair.

How To Disconnect A Car Battery

When disconnecting the battery, keep in mind that you are dealing with a hazardous substance found inside the battery, the sulfuric acid solution called electrolyte. You will need some protection such as rubber gloves and protective goggles when working with a battery. Wearing a long-sleeved shirt and footwear that cover the toes of your feet are also recommended.

Since sulfuric acid is a noxious substance, you should do the disconnecting of the battery in a dry and well-ventilated place or better yet, out in the open. Also, make sure that there is no open fire nearby, and have a pail of water ready to clean up spills or douse an accidental fire.

Another precautionary measure when working on a battery is to avoid wearing any jewelry such as a ring, bracelet or any metal ornament.

Other things that you will need would be a wrench, wire brush, baking soda, rags, and water.

Here’s the Step6 to remove a car battery:

Step 1 – Put the car in park mode and allow the engine to cool.

Step 2 – Find out where your car battery is located. In most cars, the battery is under the hood, but there are cars, especially the more recent models, with the batteries placed somewhere else; under the floorboard, behind the wheel well, or sometimes in the trunk.

Step 3 – Once you’ve found the battery, check out and identify the positive and the negative terminals using the knowledge you’ve learned earlier in this article.

Step 4 – Inspect the condition of the posts and caps covering the posts of the battery terminals. If you see a bluish/whitish gunk around the caps or on the cables connected to the caps, remove it with a mixture of water and baking soda using a wire brush.

Step 5 – After cleaning the terminals, start disconnecting the NEGATIVE terminal first. With the correct size socket of the wrench, loosen the nuts securing the cap and cables to the post. Pull out the cable of the negative terminal and set it aside in a safe place away from the battery.

Step 6 – Repeat the process with the POSITIVE terminal. Make sure that the cables of the terminals don’t get in contact with each other or with any metal part of the car.

Once you have successfully disconnected the car battery terminals, you can proceed with whatever you plan to do with it.

If you would like to know more about how to disconnect your car battery then please read this article i have written.


Knowing which car battery terminal is positive and which is negative is an important awareness all car owners should have. Ignorance of such an important observation could bring you grief someday.