What Happens if You Connect Positive To Negative On A Car Battery?

The negative and the positive side on a battery are clearly indicated so as to avoid wrong connection. This is to avoid damaging the battery because of complications that arise when you connect positive to negative and vice versa.

What happens if you connect Positive to Negative on a Car battery? This may cause a great amount of sparks to shower all over the place and may even cause fire.

Is there need to worry if you connect positive to negative on a car battery? Yes, the connection if left in that state for a significant amount of time will gradually cause damage to the car battery and even the car itself. Like most electronic equipment that cannot tolerate being connected backwards, the car battery may get damaged completely.

What Happens When the Battery Is Connected Backwards?

Immediately you connect the car battery in reverse into the car, you will see sparks all over the bonnet. This is followed by the car going completely dead; it will be unable to start and each and every light will go off. However, if you are lucky, your car might be having a fuse that is designed to protect it from such mistakes.

The electric current will have flowed backwards through electric systems of the car. While this is not that serious for the lights, you will need to worry in the case of electronic devices that have diodes, for instance, the Engine Control Unit. You will need a technician to come through and inspect them for diode damage.

The components of the fuses will get severely damaged and this will be followed with the blowing up of the fuse themselves. The damage could turn out to be irreversible and you might need to dig deep in order to remedy the situation at hand.

What Damage Is Exerted on the Car?

The electric system on the car will experience reversed polarity and this may end up causing serious damage in the car’s interior. This part of the car is quite sensitive and the electronic components might have to be replaced with new ones. If your car has monitors and any other electric devices, you will need to have a technician look at them so that you remedy the situation as soon as possible.

As seen from the above discussion, the damage extent depends on how long the battery is left in reversed connection. You will need to disconnect it as soon as you realize you made a mistake.

What Damaged Is Caused if You Hook the Battery Charger Cables Incorrectly?

Regular charging the car battery is advised since a battery that is always in a drained state may not last long. In the process of hooking the charging cables, one should be careful when connecting them onto the terminals. Connecting them the wrong way may cause damage onto the battery you want to charge.

For one, this causes a reverse in the polarity of the car battery. it might even cause the battery to explode in some cases. The battery may get damaged such that it will be unable to hold charge, meaning that you will have to buy a new battery altogether for your car.

On the other hand, the charger might also get damaged as a result of the wrong connection. This is because once the cables have been connected incorrectly, a wrong polarity is sent into the charging system and this causes a permanent damage as it will not be able to charge batteries as it did before.

What Ensues in the Case that Jumper Cables Are Connected Wrongly on a Battery?

Jumper cables and a charged battery come in handy if your battery dies in the middle of a drive. If you are lucky you get this done in seconds, but in some cases complications arise and you are delayed.

When doing this, connecting the jumper cables to your car battery, you need to be careful when connecting the cables to the terminals. If this is done wrongly, there will be damage and this might be severe since there is high current flowing in the system.

For one, the two batteries will be damaged after a series of ugly events occur. Connecting one battery positive terminal to the other’s negative will cause a great surge of electric current between them. The batteries will then begin heating and a lot of hydrogen will be produced from a series of chemical reactions. This is even worse for lead-acid batteries that are the most common.

The heat produced is highly destructive as it will cause both the internal and external parts of the battery to melt. On the other hand, the hydrogen gas exerts pressure on the battery casing and might cause it to crack. Some may even show bulges on the casing. In the case of cracking, the hydrogen escapes and might even ignite and explode once it gets outside.

The jumper cables are not left behind as they too will be damaged as a result of the wrong connection. They will not be able to contain the huge amount of electric surge and they get quickly heated up and hence burn the insulation. Such types of jumper cables should not be used as they expose you to harmful electric current.

What to Note When Connecting the Car Battery

It is always important for you to note that the positive terminal should be connected first before the negative terminal. This helps prevent any complications from arising. However, in the case of disconnecting a car battery, the negative side should be disconnected first. This helps to prevent a scenario of short circuiting the battery system.

Related Article: Which Car Battery Terminal Should We Connect First?


When going about connecting the car battery, it is important that you be observant of the terminals to avoid damaging the battery. This is because like any other electric device, the car might be damaged as a result of reversed connection. The battery itself will also be damaged and you could also get harmed in the whole process.