How to Tell Positive and Negative on a Car Battery

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Your car’s battery is responsible for getting power to your starter, which is needed to start the engine. If your vehicle is not starting the first thing you should check is the battery. 

If you’re getting ready to work on your vehicle’s battery you need to know the difference between the positive and negative battery terminals. Battery terminals are metal pieces of the battery that stick out on the top and they’re typically covered with rubber caps. The battery terminals are color-coded with black representing the negative terminal and red representing the positive terminal. 

Read on to learn more about your car’s battery and how to tell the difference between the positive and negative terminals.

How to Tell Positive and Negative on a Car Battery

Identifying the Positive Terminal 

On most car batteries there will be a red cover that covers the positive terminal. The cover is made of rubber and acts as a shield to protect against shorting and accidental power issues. While the cover should be present on most batteries, older cars might not have the rubber cover. The good news is that you don’t have to panic because there are other ways to identify the positive battery terminal.

If the battery terminals don’t have rubber covers, look for a positive symbol. On car batteries, the positive symbol will be displayed as a (+) sign – the symbol used for addition. Some vehicles will also have color-coded wires. If you see red wires connected to the battery, it’s the positive terminal.

If you want to identify your car battery’s positive terminal these methods are the best to do so.

Identifying the Negative Terminal 

The negative terminal is also color-coded. Instead of having the bright red color, negative car battery terminals have a black rubber cover. In some cases, vehicles will have black wires running to the negative terminal too.

Unfortunately, some vehicles won’t have a rubber cover over the negative battery terminals. Furthermore, some vehicles might use black wires for both battery terminals. If that’s the case, you can find the negative terminal by looking for the negative symbol. On car batteries, the negative symbol is displayed as (-) sign, which is the symbol used for subtraction.

Once you can tell the terminal apart you can safely disconnect the car battery and begin addressing issues with your vehicle.

What if the Car Battery Terminals Are Corroded?

Car battery terminals can become corroded over time. This is because car batteries use battery acid, which can leak out and cover the battery terminals. When this happens it can be hard to identify the positive and negative car battery terminals and almost impossible to work on the battery. 

Luckily, car battery corrosion is easy to fix and can be done with ingredients in your home.

Step 1

Before you use anything to remove battery corrosion, make sure you disconnect the battery from your vehicle. Disconnecting the battery will prevent unnecessary electrical shocks and potential injuries. When disconnecting battery terminals you need to disconnect the negative terminal before the positive terminal.

Step 2 

Next, you want to make sure the wires are in good condition and aren’t damaged. If wires are damaged or frayed, it’s time to replace them and the issue might be beyond cleaning battery corrosion.

Step 3

The final step is to apply a battery cleaning solution to your car’s positive and negative battery terminals. There are a few ways to do this but the most common methods include using household items.

To clean your car battery terminals you can use:

  • 1 teaspoon of baking soda mixed with water
  • Coca-Cola (soda contains acid that can damage engine components, so seal off the terminals before using soda)
  • Commercial-grade battery cleaners

Regardless of the formula you use, battery corrosion is easy to clean and should come off in less than 30 minutes.

Hooking Up Jumper Cables 

If you need to tell the difference between the positive and negative car battery terminals because you need a jump, you have to hook up jumper cables. While jumper cables are easy to use, hooking them up properly is important. 

We’ll break down the necessary steps to hook up jumper cables below.

  1. Check your vehicle’s owner’s manual before connecting any cables.
  2. Turn off your vehicle’s lights and other accessories. Make sure the key is out of the ignition. We also recommend letting the car sit for about an hour before working on it.
  3. Have another vehicle that’s in working order park in front of your vehicle. Make sure the cars are not touching.
  4. Connect the red jumper cable to the positive terminal on the dead car battery.
  5. Connect the other end of the red jumper cable to the other vehicle’s positive terminal (this end is also red)
  6. Fasten the black cable to the negative terminal on the working battery.
  7. Connect the other end of the black jumper cable to the non-working vehicle’s engine block.
  8. Start the working car’s engine and let it run for between 1-3 minutes. The longer it runs the better the charge will be.
  9. Start the car with the non-working battery.

When you want to remove the jumper cables you want to repeat the process of hooking them up but in reverse.

The steps are as follows:

  1. Remove the black jumper cable from the non-working car’s engine block or other metal component.
  2. Remove the black jumper cable from the working battery.
  3. Disconnect the red jumper cable from the good battery.
  4. Disconnect the red jumper cable from the non-working battery. 

Once you successfully start your vehicle let it run for about 20 minutes to charge the alternator. If the battery fails to start again shortly after it could be your vehicle’s alternator.

How Long Do Car Batteries Last?

Car batteries last for between 3 and 5 years. If your vehicle’s battery is more than 4 years old, we recommend having it replaced before you get stranded and need a jump. That said, good battery maintenance can extend your car battery’s life and help it last for more than 5 years.

When it’s time to replace your car battery you can do it on your own or bring it to a mechanic. As long as you cover the cost of the battery most mechanics will replace it for free. Mechanics can also give you more information about your car’s battery and let you know if you need a replacement.

Making the Most of Your Car’s Battery

Your car’s battery provides the power needed to start the engine. Without a car battery, you can’t start the car and if it dies you can end up stranded. Learning about how to tell the difference between positive and negative car battery terminals is the best way to get started. Once you know how to tell the difference you can start to work on the rest of your vehicle.

Questions? Contact us here.

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