Can You Run a Fridge on a Car Battery


There is nothing worse than losing all your groceries due to a power outage.  Luckily there are ways to work around even the worse blackouts. Even if you don’t have a generator, you can keep your fridge running smoothly with your car battery.

To run a fridge off of a car battery, you will need an inverter that can handle the power surge your fridge makes upon startup.  Typically a 1500 watt inverter will do.  A low energy fridge can be powered up to 5 hours without harm to the battery, even longer if you idle the car at the same time.

But, you will need the right equipment and a plan. Not following instructions carefully can result in ruining your car battery and/or your fridge: a much more costly loss than groceries.

Here’s everything you need to know about running a fridge on a car battery so that you’ll be prepared for what may come.


Related: Do you want an inverter that is sure to get the job done? Then you need to get your hands on this one. I had no problem powering up my fridge with this. I am very glad that I have it as part of my preps in case anything goes wrong.


Cobra Pro 1500w InverterOpens in a new tab.


How long does the battery last?

The first question that most people ask about using a car battery to power their fridge is how long will the battery last?

The answer is it depends. But generally, you can expect your battery to power up a small 100W fridge off and on (more on that later) for up to 12 hours. Generally, you want to stick with about five hours so that your car battery will still work in your car.

It’s important to note that an automotive battery is a lead-acid battery; running it below 50% will permanently damage the battery.

There are other things to consider when calculating how long the battery will last. If your fridge is newer, it will likely be more energy efficient than an older model. If your fridge is bigger, it will consume more power than a smaller model, burning out the battery sooner. 

Investing in a kilowatt monitor will help you see how much energy your fridge is sucking from the battery.

You can make your car battery last longer simply by turning on the engine from time to time and allowing the generator or alternator of the car to charge the vehicle’s battery.  By doing this, it might be possible to power a fridge for a couple of days on a single tank of gas.

Off and On

Yes, off and on. Fridges only run part of the time to keep cool. Even when plugged into the wall, you can sometimes hear when your fridge is running or not. According to the Department of Energy, a fridge runs about a third of the time, or eight hours a day. 

You can choose to use the battery for 20 minutes every hour, or power up the fridge every other hour, charging the car battery between uses if possible. If you run your fridge constantly on the battery, it will run out faster, in a few hours.

Risks 

There are risks to using a car battery to power up your fridge. Most of them can be avoided if you are careful and use the right equipment.

  • Burning up fridge’s compressor. Power surges or other electrical occurrences can cause this. Using the right inverter can help.
  • Killing your car battery. Remember, car batteries aren’t created to run through all their energy at once. They’re built to use a little power and be immediately recharged. Running a car battery to its absolute limit will lower its life. It’s best to run it till about 50% energy and recharge if at all possible.

Inverters

Since a fridge runs on alternating current and the battery runs on the direct current, you’re going to need an inverter. There are a couple to choose from.

We recommend using a pure sine wave inverter. Although it is more substantially more expensive, you’re not going to wreck your fridge by using it.

While modified sine inverters deliver the proper voltage, they can quickly overheat. Furthermore, the energy pattern of a sine wave is choppy, which can cause the compressor to fail over time.

You’re going to want to get an inverter with at least 1000 running watts. But preferably between 1500 to 2000 watts.

A 750 power inverter should have a peak of 1500 watts. This should be the minimum. If you get your hands on a 1000 power inverter, your chances of success are greater.

You can also buy a kilowatt to measure the amperage and wattage. Attaching an LED meter to the battery is also recommended to measure the voltage on the battery.

It’s best to connect your inverter directly to the fridge if possible. Or to use the shortest extension cord you can find. The longer the cord, the greater the voltage drop. Since you are using an inverter, you are already losing 15% of the energy. You don’t want to lose more.

Remember, it takes about four hours for food to go bad. So even if you’re running your fridge every other hour, the food should remain good.

Related: What Appliances Will A 3000 Watt Generator Run?Opens in a new tab.

LED Lights

This may seem excessive, but something as minor as changing out your fridge lights could help you save some energy, giving you more power to keep your fridge cold.

A typical fridge is fitted with incandescent bulbs; replacing them with LED bulbs can drop the electricity use of the lights from 100 W to 12 W — a substantial improvement!

Calculating KW

Every fridge is different, so the power requirements will vary from model to model. You should be able to check the hourly energy requirements of the refrigerator by checking the sticker inside or checking the manual.

A typical car battery has 60 AH capacity and 12 V. So, given that AH * V = watt-hours, you should have 720-watt-hours.

If your fridge requires 100W and only runs a ⅓ of the time, you’ll need 33 watts per hour.

Including energy loss from the inverter (15%), you’re looking at 39 watts (33W/0.85 = 38.9) being used per hour.

Keep in mind that larger refrigerators will use more energy (130 W +), and some car batteries are only 50 AH. Check in advance before making your calculation.

Materials Needed to Run a Fridge on a Car Battery

  • Pure Sine Power Inverter.
  • LED Fridge Lights.
  • Kilowatt Usage Monitor.
  • LED Monitor.
  • A Fully Charged Car Battery.
  • An Unplugged Fridge.

How to Use a Car Battery to Power your Fridge Step-by-Step

  1. Check the power requirement of your fridge.
  2. Buy a pure sine wave power inverter.
  3. Unplug the fridge.
  4. Change the lights in the fridge. The typical lights in the refrigerator suck up more energy. Replace with LEDs.
  5. Attach a kilowatt monitor to the inverter
  6. Plug the fridge into the kilowatt monitor.
  7. The light in your fridge should turn on. Your food is saved!

Resources

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Sean Jennings

Sean has been living simply Off-Grid in Hawai'i for over 18 years. He lives debt free on Hawai'i Island with his family and over 40 chickens. When he's not tinkering around the homestead, he's off exploring the shorelines for fish & surf.

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