How To Tell Which Is Positive And Negative On A Car Battery?

Don't know which is positive and negative terminal on a car battery? This guide will show you how to identify them in just a few simple steps.

Battery Terminal

Learning how to jump start a dead battery is a critical for being a car owner. To learn this, you must first know how to tell the positive and negative terminals on a car battery. If you aren’t used to working with the car battery, the two can be confusing.

So, how do you tell which is the positive and negative terminal on a car battery? The positive battery terminal is usually colored red and has a plus (+) sign posted on the cover. The opposite is true with the negative battery terminal. It may be colored black and have a minus (-) sign on the cover. You might also tell by looking at the color-coded wires heading to the terminal.

In this guide, we show you how to differentiate between the positive and negative terminals on the car battery. We also show you the right way to connect jumper cables when the battery is dead. 

What is the Positive Terminal on a Car Battery?

The positive terminal cover on the battery is usually red-colored. However, not all car manufacturers use this method. If the terminals aren’t color-coded, you can also look at the cover to see if there’s a plus (+) sign on it.

So, what do you do if the cover is missing? You are going to have to figure out the terminals another way. With some vehicles, the wires leading to the terminal will also be colored red, helping you to differentiate between the two. 

We always recommend using a multimeter to be 100% sure which battery terminal is negative and which is positive.

What is the Negative Terminal on a Car Battery?

The negative terminal on the battery is sometimes black. However, if none of the terminals are red but both are black, this can make the process very confusing for you.

In this case, you need to look and see if there is a minus (-) sign printed on the battery cover. If so, this sign indicates that you have found the negative terminal of the battery. 

The wiring insulator should also be black, with the positive side in red. This wiring is connected directly to the metal chassis of your vehicle, whereas the positive side would not be. 

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Right Way to Use Jumper Cables

While it’s easy to jump start a vehicle with a set of cables, there are some precautions that must be taken. If you mix up your jumper cable connectors or you touch the two ends together, you could end up injured or cause damage to your car. For this reason, it’s wise to understand the steps before proceeding. We also recommend wearing protective gloves and a pair of safety glasses.

Here are some basic steps to follow, but you can get more detail by reading through your car’s service manual.

  1. Attach the positive jumper cable to the positive terminal on your dead battery.
  2. Attach the other positive jumper cable end to the positive terminal on the good battery
  3. Attach a negative jumper cable end to the negative terminal on your good battery.
  4. Put the opposite end of the negative jumper cable to a ground location on the car that has the dead battery. You should look for any bare metal part that is heavy-duty. It can be on the engine or connected to the chassis of the vehicle. All of these create a good ground connection. You don’t want to place your negative jumper cable end to the negative terminal on the dead battery. If you do, sparks could ignite the fumes coming out of the battery. 
  5. Double-check all of the connections before moving forward. It’s important that everything is secure.
  6. Start up the car that has the good battery.
  7. Rev the engine of the good car until RPMs hit 1,500 to 2,000. Keep up this engine speed for a few minutes. 
  8. Try to start the vehicle that has a dead battery. It could take a couple of tries to get it started. 
  9. Once you get the engine running, disconnect the ground connection that uses the negative jumper cable.
  10. You can also remove both the negative and positive cable ends from the vehicle that had the good battery.
  11. Finally, take the positive cable end off of the vehicle that had the dead battery. 

It’s important that you don’t turn off your car engine for at least thirty minutes. The good battery only provided a surface charge to the dead battery. If you shut off the car, you will be facing the same situation over again. Instead, allow the alternator to fully charge the battery. It’s best if you can take the vehicle for a drive down the highway to get the alternator working faster. 

RELATED: What Size Jumper Cables Do I Need? (2 vs 4 vs 6 Gauge)

What Happens if Battery Cables are Hooked Up Backwards?

With the jumper cable polarity altered, there’s a big difference in the electrical current that’s flowing to each. Because of this, it’s possible to melt the cables or cause a car fire because of the difference. For this reason alone, it’s very important that you always hook up the battery cables the right way.

The good news is that automakers realized this was a common problem for people that don’t understand car batteries. Therefore, many manufacturers install a main fuse that will blow before these problems occur. The best case scenario is that you blow the main fuse by hooking the terminals up wrong. If that’s the case, you can simply reverse the cables and replace the main fuse to get back on the road.

READ MORE: Battery Terminal Corrosion Causes (How to Fix & Prevent It)