Galvin Power is reader-supported. When you buy via our links, we may earn a commission at no cost to you. Learn more

How to Wire an Extension Cord to a Car Battery? – 2 Steps

Written by Edwin Jones / Fact checked by Andrew Wright

how to wire an extension cord to a car battery

Attaching another wire to a vehicle’s power bank can be a good idea if you want additional power for your electronic devices. But now you’re wondering how to wire an extension cord to a car battery.

You typically need an inverter to do this task properly. Moreover, the inverter, power strip, and the electronic device you’re going to use should pair well with the battery.

So continue reading to gain insight into using a power strip with your vehicle without significant risks of running into problems.

Step-by-step to Wire an Extension Cord to a Car Battery


Before continuing this project, take note that connecting a power strip to a car battery means knowing the maximum amperage and voltage ratings allowed for the setup.

Generally, a standard 12-volt battery can supply 48 amp hours of power. That means that the power strip shouldn’t have an amperage and voltage rating higher than the vehicle’s battery. Otherwise, an overload may ensue, causing both objects to fail.

Apart from knowing the maximum load to apply, other safety measures that you need to consider are:

  • Always pull the plug from the extension cord when disconnecting it from the outlet. Don’t pull the wire.
  • If the battery is still in the car, don’t move the vehicle while the extension cord is still in the outlet.
  • The extension cord should be in good working condition before using it. If not, replace it with a new model.
  • Avoid using the extension cord attached to your car’s battery during hotter-than-average weather. Doing so may increase the risk of fires.
  • Only connect electronics with relatively light power requirements, such as a small electric fan, to the power strip attached to the car battery.

After taking note of these preventive measures, continue reading to know the steps to wire an extension cord to your car’s battery:

What To Prepare

Step #1: Attach The Wires

Connect and secure the wires that should come with the inverter kit to the inverter and the car battery. Pay attention to the wire’s colors as they should match with the terminals. For example, the red wire should go to the same-colored terminals.

You may use car battery extension cables instead of the wires in the inverter kit for this step. But you may still need to calculate for the correct power ratings to prevent problems.

Warning: Crossing the wires or placing them in the wrong terminals can cause a massive power surge. This event can result in severe heat produced, leading to overloads and fires.

Step #2: Plug In The Extension Cord

Connect the extension cord to the inverter. Make sure you’re placing it in the right terminal. At this point, you may also connect your electronic devices to the power strip.

Then, turn on the inverter. Turn on the attached electronic devices to see if the setup works as intended.

If you want to disconnect the extension cord from the battery, turn off the electronic device first. Next, turn off the inverter unit before removing the wires.



What Are The Characteristics Of A Car Battery?

The main characteristics of a car battery are:

  • Accumulator capacity: The ampere-hour upon discharging the battery to the minimum allowable voltage reading.
  • Cold cranking amps (CCA): The required current for the battery to start the engine in a cold environment.
  • Self-discharge: The battery’s normal capacity reduction.
  • Electromotive force (EMF): The voltage at the car battery’s terminals.
  • Charge level: The resulting measurement when taking into account the EMF and electrolytes.
  • Internal resistance: Indicates the measurement of resistance in different components, such as the electrodes, leads, and separators.
  • Polarity: The characteristic of having positive and negative terminals.

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

You can attach a power strip to a car battery if you need to use low-powered electronics with that source.

However, directly connecting an electronic device to the vehicle’s battery won’t yield results. It’s because car batteries usually run with DC electricity. You need the inverter to convert that power to AC for your electronics.

On that note, if you have an electric vehicle, know that you shouldn’t charge a car battery with a wall outlet. You’ll still need to reduce the voltage from the source with a transformer or rectifier.

How Do You Hook Up An Outlet To A Car Battery?

Connecting a car battery to power outlet is a relatively straightforward job of using a compatible inverter. This device will have one or multiple outlets so that you can use the vehicle’s battery as a power source.

However, you need to pay attention to the following guidelines:

  • Connecting more than one device to the inverter can reduce the battery’s capacity faster than usual.
  • It’s ideal to use electronic devices with the inverter and car battery for a reasonably short period.
  • Only use an inverter designed for 12-volt batteries.
  • Take note of the wattage of your electronic devices to prevent problems like blowouts.

If done correctly, it’s also possible to connect a wall plug to a car battery. But remember not to forget about the mentioned safety measures to ensure a proper and harmless connection.

Can I Plug A Car Battery Charger Into An Extension Cord?

It’s not advisable to use an extension cord for the car battery charger. Although the connection may work, the charger may melt or catch fire if it encounters more power than its capacity.

But if you want to go ahead and do this anyway, use an extension cord for a battery charger with a trickle feature. That way, you can maintain the polarity of the connection and prevent possible hazards.


Now that you’re at the end of this post, you should now have an idea of how to wire an extension cord to a car battery. Remember, you need to pay attention to the amperage, voltage, and wattage requirements of the setup.

Failure to take note of these important particulars can result in overloads and fires. These problems can also appear if you cross the wires connecting the battery to the inverter.

Read next: 4 Easy Steps to Replace an Extension Cord Plug.

5/5 - (3 votes)