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How To Tell Positive And Negative On A Car Battery

How To Tell Positive And Negative On A Car Battery?

Working with the vehicle’s battery and electrics requires excellent concentration and attention to detail. Small mistakes can lead to unexpected problems.

The essential thing is to distinguish the cathode and anode of the car battery. That can help you deal with battery-related issues safely and adequately. Determining is also relatively easy but will be a bit confusing for beginners. This article will introduce How to tell positive and negative on a car battery and some standard battery handling methods.

Why Do You Need To Distinguish The Positive And Negative?

You may not know, car batteries are usually lead-acid batteries and have a voltage of about 12.65 volts. The role of the battery in the vehicle is to provide the initial current to start the internal combustion engine after the key is plugged in.

If you want to learn more about the operation of batteries and types of batteries, you can refer to “positive and negative battery: operating principles and guides”.

Distinguishing the 2 poles of the battery is the first step you need to know to preserve, repair or replace a new battery. You need to attach the correct cable to the correct polarity to ensure proper battery operation.

If the two poles are confused, a thermal reaction will occur that will ultimately damage the battery. This also has the potential to explode the battery and the vehicle, endangering people.

How To Tell Positive And Negative On A Car Battery?

How To Tell Positive And Negative On A Car Battery

There are many different types of batteries and battery brands, making it challenging to identify the polarity of each battery type. But don’t worry, with these 4 simple ways to recognize it, you will become an expert in this matter.

The + and – symbols on the top of each battery terminal

The first sign that can help you distinguish the two battery terminals is the “+” sign near the positive terminal and the “-” sign near the negative airport. The + sign represents the positive pole, and the – sign means the negative pole.

Because the symbol is printed on the battery cover, the size is small and the same color as the battery cover, it is sometimes difficult to notice without looking closely.

Identification based on the color of each pole

A more intuitive way of distinguishing is based on color. As a general rule, red will represent the anode, while black or blue represents the cathode. Depending on the battery type, the color may be painted on the cable or the plastic cap that protects the battery terminal.

It is the most straightforward distinction and can be to almost all car batteries. You have to remember: red-yang, black-yin.

Difference in diameter of cathode and anode

The third way to distinguish is on the diameters of the two poles. At first glance, the two electrodes appear to be the same, but you will see that they are not equal when you look closely. The anode is slightly larger in diameter than the cathode (positive-large, negative-small).

This method is challenging to apply because it is easy to get confused if not closely observed. So let’s rely on color first. In the case of non-color-sensitive batteries, use this method.

Use a voltmeter to measure voltage

If the above 3 methods do not apply, you can use a voltmeter to determine the polarity of the battery. A voltmeter is an instrument used to measure the potential of an electric current. The machine has 2 cables connected to 2 needles corresponding to 2 poles: the red cable is the positive pole, the black cable is the negative pole.

To determine the positive and negative poles, you need to turn on the voltmeter. Select DC (direct current) mode. Then put the two needles of the voltmeter on the 2 terminals of the car battery.

If the voltmeter display shows a negative number (-12.65V), the pole attached to the red needle is the negative pole, and the pole attached to the black hand is the positive pole.

Conversely, if the voltmeter display shows a positive number (12.65V), the pole attached to the red needle is the positive pole, the pole attached to the black hand is the negative pole.

This method is a bit confusing but always gives accurate results.

How To Check If The Car Battery Is Still Charged?

How To Check If The Car Battery Is Still Charged
A common problem with most cars is that the car battery fails due to insufficient voltage. If left for a long time, the battery may die. There are also cases when using the voltage measurement method as above and giving fully charged results (12.65V), but the battery is still damaged.

The only way to check if the car’s battery is good is to measure the battery’s voltage when starting the vehicle. To check, you need to follow these steps:

  • Step 1: Turn on the voltmeter and select DC mode.
  • Step 2: Attach the red needle of the voltmeter to the positive terminal, the black arrow to the negative terminal.
  • Step 3: Start the car.
  • Step 4: If the measurement result is more significant than 9V, the battery is still good. If the result is below 9V, you should replace the battery with a new one to avoid trouble later.

How To Replace A Car Battery?

To remove the battery from the chassis, remove the 3 screws that secure the battery. In which, there are 2 screws on the 2 terminals and 1 screw that holds the battery to the base.

However, many cars today, if the power is off, will cause unexpected problems. You can avoid it by using KAM (Keep Alive Memory) – a device that provides temporary power to the vehicle when the battery is disconnected.

Steps to replace car battery:

  • Step 1: Connect KAM (if you find it necessary)
  • Step 2: Remove the screw securing the battery to the base first.
  • Step 3: Next is to remove the screw of the negative pole.
  • Step 4: Finally, remove the screw of the positive pole.
  • Step 5: Remove the old battery and insert the new battery.
  • Step 6: Attach the screws in reverse order: positive pole, negative pole, and screw fixed to the base.
  • Step 7: Done.

How To Jumpstart A Car That Has Run Out Of Power?

In many cases, the car battery runs out of power due to long-term non-use or suddenly turns off due to not taking good care of the car battery. In such cases, you cannot take the car to a repair shop or replace the battery. Don’t worry, and you can recharge your vehicle with an electric vehicle or a portable generator.

Things you need to prepare:

  • An electric car or a generator.
  • 2 cables to connect 2 batteries or booster cables.

Implementation steps:

  • Step 1: Connect the positive pole of the dead battery to the positive pole of the live battery or generator. Do the same with the cathode.
  • Step 2: Start the car with electricity or a generator. Wait 20-30 minutes.
  • Step 3: Start the car with no power and wait for about 5-10 minutes.
  • Step 4: Now that the engine can start, you can remove the booster cables.

Note: please wear gloves before performing for safety.


Through this article, you also see the importance of distinguishing the positive and negative poles of the car battery in checking the battery, replacing the battery, or jumpstart a car. Just now, there are 4 ways on how to tell positive and negative on a car battery.

I hope you will no longer have to be confused about the cathode and anode when looking at the car battery and successfully dealing with the battery problems.

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