How to Run a Household Fan on a Car Batteryby Bryan TrandemUpdated August 30, 2017
In an emergency situation or in other unusual circumstances, it's possible that you might want to run a household fan off a car battery. For example, during a power outage during a heat wave, or should someone fall ill with fever during a camping trip, being able to power a fan to offer a cooling breeze might be of great benefit.
It is entirely possible to operate a fan and some other household plug-in appliances by powering them off a car battery, but it takes some special equipment, as well as some understanding of electrical systems.
Some people with an interest in preparedness choose to keep several standard automobile batteries on hand and charged up for use with an inverter in emergency situations. It is also possible to use an inverter on the car battery that is currently connected to your car.
Items you will need
12V power inverter with electrical input clamps
Direct Current (DC) vs Alternating Current (AC)
First, it's important to understand that the electrical system that powers your car is not compatible with the electrical system that powers a household fan or other plug-in appliances. Your car, as well as other devices that operate by battery power, use a direct current (DC) system that operates with 12 volts of current. Most household plug-in appliances, on the other hand, operate with 110-120 volts, and the current is alternating—meaning that there are two pulses of electricity passing through the wires, flowing in alternating phases.
So a household fan or other standard appliance cannot be powered directly by the relatively small amount of power in a DC battery. Not, that is, unless you add a power inverter/converter that transforms the 12-volt DC current into 110/120volt AC current.
Fortunately, such devices do exist, and owning one for emergency situations is a good idea. Not only can it be used for powering a simple household fan, but it can allow you to use your car as an emergency generator to power a radio, to recharge cell phones, or to power lights or other essential appliances.
To make this possible, you will need to buy a power inverter specified to convert 12VDC power into 120VAC at 60 HZ.
Traditionally, a 12-volt power inverter is connected directly to an automobile battery through clamp connecters—the positive lead connecting to the positive pole on the battery, the negative lead connecting to the negative pole. Many modern converters, however, also have a plug connector that can be inserted directly into the cigarette lighter/ auxiliary power plug in your car. This can be used, for example, to power a DVD player or other appliance from a battery connected to the car. This even allows you to use the inverter while driving. Many a restless child has been entertained on long car trips with a DVD player plugged into a power inverter.
Some inverters now also include USB ports that also allow you to charge cell phones, tablets or other electronic devices that use USB connections. This can also be of great benefit during emergencies.
A 12-volt inverter is for use on automobile batteries or other vehicles that may use a 12-volt battery, such as a boat. Never use an inverter on larger batteries, such as 24-volt batteries.
Using a 12-volt Inverter
Here's how to use a 12-volt inverter in the traditional manner, with connector clamps.
Ensure that the power switch on the power inverter is in the OFF position. Connect the inverter's positive input clamp (red) to the positive battery post (+) on the automobile battery. Connect the negative input clamp (black) to the negative battery post (-) on the automobile battery.
Turn the fan power switch to OFF. Plug the fan into the power inverter. (The same holds true if you are using the inverter to power a different device, such as a radio—make sure the device is in the OFF position before you plug it in. )
Turn the power inverter switch to the ON position. Allow the power inverter approximately three seconds to charge up. Turn the fan switch to one of the ON positions ("Low," "Medium," or "High"), and place the fan where you want it.
When disconnecting the fan, reverse the process: turn the fan OFF first, then turn the inverter to the OFF position, then disconnect the inverter, beginning with the negative lead (—).
Since a fan is an inductive load (in other words, it has a motor that initially pulls a higher electrical load before settling into an operating load), it is important to choose a power inverter with a continuous power rating greater than the fan's maximum power setting. For example, if the maximum power setting is 120V AC, 1.5 A, the fan's maximum power draw is 180 watts. A power inverter that is rated for 180 watts or more continuous power is appropriate for this application.
Bryan Trandem has more than 20 years of experience writing, editing and publishing nationally known books on home improvement, landscaping and gardening. He holds a graduate degree from the University of Minnesota, and is a former Master Gardener and acknowledged home improvement expert.