When Connecting a Battery Which Terminal First? A Breakdown

When connecting a battery which terminal first is a common cause of confusion. Although some people claim that it doesn’t matter because no circuit is created when only one wire is connected, it’s always best to err on the side of safety. Although the battery is not used in the circuit, it is still possible to complete the circuit.

When Connecting a Battery Which Terminal First


This complete guide explains all you need to know about connecting your battery terminal.

Which Battery Terminal Must Be Connected First?

The battery’s positive terminal must be connected first to the live battery’s positive terminal. Then, you should attach the live battery’s negative terminal to a grounding point on the vehicle (e.g., chassis). This completes the circuit and electrical current can move across the live battery to the dead battery.

Battery Cables Connected Backwards

The fuse explodes if battery wire cables are connected backward, cutting off the circuit’s ability to conduct electricity. The electrical system in your car has fuses as a safety measure. They prevent damage to your car by cutting the circuit in the case of an overload of current. 

– 12V Battery Connected Backwards

The electrical system of your car won’t be damaged if you connect a 12V battery backwards. However, it will stop the battery from charging. This happens because the battery’s polarity will be flipped, and electrons will flow against their natural direction.

– Working Principle of Correct Battery Connection

The working principle of a car battery involves the generation of electric current by an alternator when the engine is on. This charges the battery, allowing electrical current to flow across the positive terminal to the negative battery terminal.

Whenever the engine is off, the battery powers the car’s electrical system (e.g., lights, radio, etc.). The battery achieves this by releasing electrons into the electrolyte and onto the negative plate. As a result, current flows from the positive terminal to the negative terminal.

You should connect the positive battery terminal wire first because the negative is the ground wire. As you try to connect the positive wire, you should avoid connecting the ground wire first, as doing so will complete the circuit and could cause sparks.

These sparks could shock you or even short out the battery or other components. It’s imperative to begin by connecting the positive first for this reason. No sparks will fly when the earth is connected after the positive because the current will flow into the ground wire. Doing this will protect you when you connect the cords, in addition to keeping the components of your car or other equipment secure.

– Battery Cable Color Codes

Battery wires generally have color coding. The negative terminal is black, and the positive terminal is red. To be sure, it is always smart to consult the owner’s manual for your vehicle. Remember, though, that the polarity of the terminals does not always match the color of the wires.

– Proper Order When Disconnecting a Car Battery

The negative terminal should always be disconnected first when removing an automobile battery. This is due to the terminal’s connection to the grounded car’s chassis. If the positive terminal were first disconnected, the positive terminal would become connected to the chassis, causing sparks and potentially harming the engine.

Notice that the order of attaching and detaching the terminals is reversed. This is because you interrupt the circuit when you disconnect the battery. Sparks or electrical system damage are therefore not a possibility.

– Starting With the Negative

Do not start with the negative terminal because of safety risks. To prevent electrocution or fire from starting, it is always positive before negative. But at this stage, it’s essential to distinguish between positive and negative on a car battery. Positive and negative signposts are denoted by (+) and (-), respectively.

Now, if you attach the positive cable first and make the slightest error, touching the car’s frame or any other metal component with the wrench used to tighten the positive cable may shock you and even start a fire. Therefore, it is crucial to adhere strictly to the specified process for connecting a car’s battery. If you’re a DIYer, this is pretty simple. If not, it would be best to request the services of a knowledgeable vehicle specialist.

– Why the Negative Terminal is Detached First

The negative (grounded) terminal is detached first to prevent a battery dead-short. Otherwise, touching the car’s frame or another grounded metal surface with the wrench used to detach the positive line could cause an electric shock or fire.

Why the Negative Terminal is Detached First

This implies that detaching the positive cable first endangers you and the vehicle. This is due to the possibility of a shock or fire occurring if the tool used to cut the cable contacts a grounded metal surface on the car. Therefore, make sure to connect the battery connections in the correct order.

– Installing a Car Battery in the Correct Order

You can install your car battery on your own following some simple steps. While self-installation is definitely possible, take note that you may need the services of a professional if there are sparks or other noticeable faults in the car engine.

The process of installing a battery is pretty straightforward. Just carry out the following actions:

  • The old battery’s negative terminal should be disconnected
  • The old battery’s positive terminal should be disconnected
  • Remove the vehicle’s old battery
  • Put the fresh battery in the vehicle
  • Connect the new battery’s positive terminal
  • Connect the new battery’s negative terminal

After installing the new battery, you might be asking how to keep the battery’s lifespan longer than average. You can increase a battery’s life by keeping it in the right environmental and working conditions. Fortunately, this is easy to do and you only need to make simple changes. However, there is only so much you can do, and you will stilll need to consider replacements after five years.

These are a few things you can do to increase the life of your automobile battery:

  • Keep the battery corrosion-free and spotless
  • Keep the car battery terminals secure and corrosion-free
  • Charge the battery regularly
  • Don’t discharge deep

Jump Start a Car in the Correct Battery Order

You can jumpstart your car with a functioning battery, and this is usually done when all efforts to start your engine with your battery has failed. The procedure for jumpstarting your car is not complicated, but you must ensure you use a functioning battery for the jumpstart procedure.

The following steps can help jumpstart your vehicle.

  • The positive terminal of the functioning battery should be joined to the positive terminal of the dead car battery.
  • The negative terminal of the functioning battery should be joined to the negative terminal of the low battery.
  • Start the vehicle with a functioning battery.
  • Give the car a few minutes to run.
  • The low battery’s negative terminal should be disconnected.
  • The low battery’s positive terminal should be disconnected.
  • Turn your vehicle off.
  • Repeat these steps if your automobile won’t start. You should have your battery changed if your car still won’t start. Anyone can jumpstart a vehicle because it is such a simple operation. Just be careful to take into account all safety measures.

– Factors That Can Harm an Automobile Battery

Extreme heat, severe discharge, and overcharging can all harm an automobile battery. Improper terminal connections are also detrimental to battery health. When the charging system’s voltage surpasses 14.0 volts, overcharging occurs. This may occur if the voltage regulator or alternator is broken.

When the battery is deeply depleted, its voltage falls below 12.0 volts. This happens if the vehicle is sitting for an extended amount of time or the electrical system is under a lot of strain (e.g., by lights, heated seats, etc.).

The electrolyte in car batteries can freeze or boil at extreme temperatures and harm the battery. It’s essential to keep the battery warm in cold temperatures (but not too hot). The battery also needs to be kept cold in warmer weather.

– When To Change a Car Battery

The battery in your automobile should be changed within three to five years, even if you take good care of it. If you reside in a hot region, you should change your battery more frequently, as the physical factors hasten battery deterioration.

When To Change a Car Battery

If you also notice that your car is hard to start or that the electrical system isn’t performing as well as it once did, then it’s time to change your batteries. Take your car to a mechanic or an auto parts retailer to have the battery tested on your automobile.

If your car battery is older than three years, it is a good idea to have your car battery changed. If you do this, you will avoid getting stuck with a dead battery. Always connect the positive terminal of a car battery first. Damage to your battery and electrical system will be avoided by doing this.

– When To Disconnect a Car Battery

An automobile battery can be disconnected at any time. However, some automobiles’ computers need to be reset when the battery is detached, and this is a little tricky. For more information on disconnecting your car battery, refer to the owner’s manual of your car.

When you want to leave your automobile unattended for a long time, it is better to disconnect the battery. By doing this, the battery won’t be discharged. Disconnecting the battery before working on your car’s electrical system is also smart. This will stop your vehicle from receiving unintentional shocks and damage. Always reconnect the battery before starting your car.

What Happens if Jumper Cables Are Connected Backwards?

If jumper cables are connected backwards, it can cause permanent battery harm, gadgets may catch fire, and there might even be a possibility of severe physical injury. The car, the battery, and the quality of your cables all play a role in what will happen when cables are connected improperly. 

If you mistakenly link up the cables incorrectly when jumping an automobile, the following may occur:

– Fusible Link Failure

Fuses (or fusible links) are used to protect the circuit between the battery and the vehicle’s electrical system. One or more blown fuses result from connecting the battery cables the wrong way. Until the blown fuse is replaced, the impacted circuit will not operate properly.

Fusible Link Failure

– Faulty Battery

A burst of electrical current is produced when the battery wires are turned around, and the battery is easily harmed. This can cause the battery to become faulty and stop working.

– Worn-out Cables

The quantity of electrical current flowing through the jumper cables dramatically increases when you reverse their polarity. The cables could therefore melt or catch fire.


Our article has explained things you should and should not do when connecting a battery terminal. Let’s have a quick review.

  • The low battery’s positive terminal should first be connected to the live battery’s positive terminal. 
  • A battery has six cells, each with a positive and negative plate. An electrolyte separates the plates (sulphuric acid and water).
  • An automobile battery can be unplugged at any time. However, some automobiles’ computers need to be reset when the battery is detached.
  • While the engine is on, the alternator generates an electrical current and charges the battery.

Remember, maintaining your battery’s cleanliness, keeping it free of corrosion, keeping it charged, and avoiding high temperatures will all help it last longer.

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