You all know about car batteries. It is placed in a car for various purposes during the engine off state. People often ask how to or can I wire an extension cord a car battery?

You can wire an extension cord to a car battery but you cannot connect it directly to an outlet. Because it is a 12 V battery while the outlet has 120 or 220 V. But you can wire the extension cord to connect the battery to other low voltage appliances.

I am going to give a glimpse to the facts here to help you understand better. First of all, we have to know the characteristics of a Car Battery and Extension Cord.

What Are The Characteristics Of A Car Battery?

Car batteries are DC sources. It has two terminals- a positive and a negative terminal. DC batteries have two main characteristics, they are:

  • Rated Voltage (V)
  • Rated Ampere-Hour (AH)


The rated voltage of a car battery is only 12 Volts DC. The voltage surges as a pressure or energy that makes the current flow through the path. Since it is a DC source we cannot directly connect a battery to an AC source or appliance that runs by AC current.

Ampere Hour:

Ampere-Hour is another important characteristic. It indicates how much current can a battery supply for how many hours. It is the multiplication of Ampere and Hour.

Suppose a battery has an Ampere Hour rating of 6AH. It means if it has to supply 6 Amperes continuously, it can supply for 1 hour.

If it has to supply 3 Amperes continuously, it can supply for 2 hours. So, The Ampere Hour indicates the current capacity and the backup time of a battery.

What Is An Extension Cord?

An extension cord is a connecting cord. It can create connection between devices, outlets and other electrical components. A common use of it is to connect devices to outlets in distant places where the device cannot reach by its power cord.

Extension cord can be of different types depending on its capabilities to carry current and the length of it. The characteristic of an extension cord is indicated by a term “Gauge”. What is a gauge?

Gauge is the American Standard value for Extension Cords. The gauge value indicates the current capacity and the maximum length of a cord. The current capacity and the gauge value has an inverse relationship. Like-12-gauge cords can carry more current than a 14-gauge cord.

Can We Wire An Extension Cord To A Car Battery?

The answer can be both yes and no. It depends on what is your purpose to wire the cord to the battery. As I have mentioned earlier car battery is only a 12V DC source. So, we must wire the extension cord between the battery and appliances that works with 12V DC current.

If we do otherwise, like, wiring the battery to the outlet directly, it will burst and result in severe damages. Because the outlet contains 120 V AC. Wiring the battery to other 120 V AC appliances will not work either.

When Can We Wire An Extension Cord To A Car Battery?

Mainly we can use it in case of a 12V DC appliances, like- DC fan, LED lights, etc. We can also use an extension cord, if needed, to connect the battery to an inverter. The inverter converts the DC into AC. Then we can use it for AC appliances.

You can also use an extension cord to connect the battery to the charger. The battery charger also provides a little more than 12V for the battery to charge. It is seen that a supply of about 16 V makes the battery heated up. So, be careful about the voltage you apply to the battery.

How To Wire An Extension Cord To A Car Battery?

There are clips or plugs found in extension cords known as jumper cables. You can simply connect one side of the cord to the battery terminals using those clips. The other side of the cord has a different port. It is plugged into appliances or inverters.

Extension cord with jumpers
Fig 1: Extension cord with jumpers

Such a type of extension cord is shown in fig 1. The jumpers are used to connect the cord to the positive and negative terminals of the battery. The other side of the cable is used to plug into inverters or DC appliances.

Things You Should Not Do:

As I have said earlier, you cannot wire the battery to anything you want. There are certain things you should never do even in your dreams. Let’s see what they are-

  • Do not connect the battery directly to the AC outlets. The AC outlets contain 120 Volts. The battery may burst if you try to do so. If you want to connect the battery to the outlet, you need to put an adapter in between. So that the 120 V is reduced to 12V DC.
  • Do no connect the battery to the AC appliances. First of all, the battery is only 12 V DC source. The AC appliances have a rating of 120 V AC. So connecting the battery to them will result in nothing.
  • Do not short circuit the battery. Car batteries have a good current rating. If the terminals get shorted, things will get worse. There is always a chance for fire or explosion. So, while connecting the jumpers to the terminals, keep this in mind.
  • Do not connect the battery to a much higher voltage source for charging. DC batteries are very sensitive. It is seen that with a little higher voltage than 12V supply, the battery starts heating. Just imagine, if you increase the voltage what may happen!


I hope you find the answers you were looking for in this article. Car batteries can be connected to devices that run with a low voltage as same as the battery’s rated voltage.

So, wiring an extension cord is totally ok, but you should always be careful about what are you choosing to connect to the battery through the cord. It’s a very simple thing to do. Give a try anytime. For any inquiry, I am here to help.

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