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Which Car Battery Terminal to Connect first: You Need to Know

There are lots of reasons that can cause people to switch car batteries or change old car batteries. No matter how you removed your car battery, it raised a common question when you went back to test the new car’s battery.

People argue whether we must connect the negative wire first or the positive wire. After reading this article, you’ll find the answer and a justified explanation for this problem.

Which car battery terminal to connect first?

Among positive and negative terminals, people often get confused about which one to complete first. There is a general opinion that it does not matter which terminal to connect to first. The reason is, no circuit is formed by joining a single terminal.

But the fact is, the terminal can be complete even with connecting the single terminal. Thus connecting the wrong terminal may cause a spark in the engine or even a blast.

So, which car battery terminal to connect first?

The answer is the positive battery terminal.

But Why? Let’s explore further:

Why connect the positive battery terminal first?

The negative terminal is connected to the ground wire. If the ground wire is connected, the circuit will be complete. Thus, the spark is formed in between the electrodes of a car battery. It may cause an explosion or damage the battery.

Thus, to avoid any damages, it’s good always to connect the positive terminal first. But why? Let’s check further:

What will happen when we connect the negative terminal first?

In general point of view, there are two points at which the spark occurs. The first point is the positive terminal, and voltage flows to the negative terminal through the negative clamp. The second point is between the electrodes of a car’s battery.

When we connect the negative terminal first, and then we turn on the ignition, it causes a current flow from the engine’s ground wire to positive terminals and then another current flow from a positive terminal to the negative terminal through a car battery. It causes a spark between the electrodes of a car battery and the ground wire. As mentioned earlier, the spark may cause an explosion or damage.

In short: connect the positive terminal first.

Now you understand that connecting positive terminal first is safe for your vehicle, but why is it safe? Let’s find out more.

Why is the positive terminal used first?

As mentioned earlier, the negative terminal forms a circuit by connecting it with the ground wire. Thus, when we connect the positive terminal first, it will break or stop the current flow between the electrodes.

Thus, this makes a positive terminal safe to use before connecting anything else.

11 steps to connect your car battery

  • Turn off the ignition, headlights and all other switches (turn off as many as possible). It will ensure that there’s no power flowing through the car’s electrical system. If you have access to a battery disconnect switch, then use it.
  • Make sure that you have disconnected your car from its battery. As a safety measure, disconnect one cable from the battery and wait for a few minutes.
  • Connect the positive terminal(red cap) first and cap it with a new plastic cap. Use gloves to protect your hands from current flow through the car battery.
  • Wait for 10 seconds before connecting any other terminals
  • Connect the negative terminal(black cap). Cap it with a new cap too
  • Check whether your car battery terminals are connected to the cables properly. If they aren’t, there may be an electrical shock to you
  • Start your engine and wait for a few minutes before checking your battery’s condition(ensure that you have not forgotten any connections). If everything is fine, then check all the electrical devices of your car. If everything is okay, you can take your car to the service station for a further check-up.
  • After checking the battery’s condition, disconnect all terminals from the car battery and remove the caps from the cables.
  • Wash off the soot on the terminals with a solution of baking soda and water or a solution of water and vinegar
  • Always use gloves and safety goggles. Doing this will reduce the risk of electrical shock to you.
  • Avoid touching your car battery terminals with bare hands as much as possible. We all know that car’s electrical system generates a lot of heat, so we can’t tell how hot it is until we touch them with bare hands.

Which terminal to connect to first while jump-starting a battery?

When you jump-start your vehicle, the above rules apply. All you need is to connect positive and negative terminals next for a successful jump-start of your car battery.

So it’s good to use these steps when you’re jump starting a dead battery with another one:

One end of the positive jumper cable is connected to the positive terminal of a dead battery. One end of the positive jumper cables is connected to the positive terminal of the new battery. One end of the negative jumper cables is connected to the negative terminal of the healthy battery.

One end of the negative jumper cables is connected to the engine block or metal part away from the battery under the hood, away from fuel lines and then combined with the dead battery negative terminal.

What is the rule for disconnecting the battery cable?

While disconnecting the battery cable, the opposite of this rule shall be followed. Disconnect the negative cable and then positive cables. It will keep you safe from any spark.

Frequently Asked Questions

Do you hook up positive or negative on a battery first?

When hooking up jumper cables, you always want to connect the positive cable or positive terminal first. It will protect you from any sparks which can damage your eyes.

Should I connect red or black wire first?

The black wire should be connected first. Once the black is connected, you can connect the red to ensure no sparks.

Why should you disconnect the negative battery terminal first?

To prevent any damage to your car’s electrical system, you need to disconnect the negative terminal on the battery first. It will reduce the risk of arcs or sparks, which may cause damage.

Is it safe to work near a car if I am using jumper cables?

If you are using jumper cables while working on your vehicle, make sure that the battery you are using is a good one. It will protect you from any arcs or sparks which may damage your eyes.


Always connect the positive terminal first. It is because connecting the positive terminal first will stop current flow between electrodes of a car battery and make it safe for you to work on the car’s electrical system.

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My Name is Christopher Angels, and I am a postgraduate in mechanical engineering. Cars have always excited me as a child, and soon I decided to dive into the world of cars by pursuing mechanical engineering. I also worked as a Mechanic for over 3 years to understand Cars' anatomy and how each part contributes to its working.

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