How to Run a Chest Freezer With Battery Backup

Power outages during a disaster can be nerve-wracking. Imagine your freezer full of nutritious food suddenly at risk, along with the money you invested in stocking it. As a prepared parent, you know keeping your family safe includes keeping their food fresh. This article will equip you with a plan to create a quiet backup power system for your freezer, ensuring peace of mind and a steady supply of healthy meals – no matter the emergency.

How to Run a Chest Freezer on Battery Backup

Two quiet ways to keep a chest freezer running during a power outage:

1. Build your own system: a deep-cycle battery (AGM, gel-cell, or lithium), an inverter, a charger, and optionally solar or wind panels to keep it topped off
2. Buy an all-in-one portable power station, which combines the battery, inverter, and charger into a single unit, easiest to do

Both options run silently, unlike a gas generator, and freezers use surprisingly little power. Most freezers pull well under 2 amps once they’ve hit freezing temperatures. The compressor isn’t running nonstop, it’s cycling on and off to hold a steady temperature.

When the power goes out, one of the first things I think about isn’t the lights. It’s the freezer. Every year we invest a lot of hard-earned money to purchase beef from a local rancher. All that carefully stocked meat, along with my stash of frozen butter and vegetables means I literally can’t afford for it all to go bad in a power outage.

The good news? With a few simple strategies, most of them inexpensive and easy to put in place ahead of time, you can protect your freezer food and avoid the stress of wondering what’s still safe to eat. A battery backup for a chest freezer is a must.

Two Ways to Provide Quiet Backup Power to Your Freezer

We’re going to talk about two main ways of providing quiet backup power to your freezer: a battery-charger-inverter setup, and an all-in-one portable power station. In addition to what I’m explaining here, there are hundreds of online videos and web pages that will help you build your system. At the end of the day, it’s not that difficult and you can spread the cost of buying individual components over several months if needed.

Run Silent: Battery+Charger+Inverter+Solar and/or Wind

This quiet backup power system works as follows:

1. The deep-cycle battery stores a significant amount of energy
2. The Inverter can convert the battery power into standard 120 volt AC power
3. A transfer switch transitions to battery power upon loss of grid power
4. A separate or integrated charger keeps the battery optimally charged; and
5. Solar panels and/or wind generators feed the battery charger.

What You Need

This backup power setup maintains your frozen food quietly, which in an extended crisis won’t attract potential predators with the loud noise of a portable generator. Here’s how to quickly build a quiet way to power your freezer if grid electricity is not available:

• Start with a deep-cycle 12 volt battery, preferably a “gel-cell” or “AGM” type; both of these types are sealed to avoid the discharge of flammable hydrogen gas which occurs in cheaper batteries. It should have a capacity of at least 100 amp-hours (Ah) and preferably have screw terminals for easy installation.

• Use an adequate-sized 12 volt to 120 volt Inverter, based upon the power need of your freezer and any other loads you need backed up. For instance, I have my house alarm backed up by the same system as my freezer. In my case, a 500 Watt sized Inverter is plenty of capacity for my 132 Watt freezer and my 60 Watt alarm power supply.

• A Transfer Switch is optional but recommended, and can be a separate unit or integrated into the Inverter or Battery Charger. This small additional cost can literally save your bacon if the power fails while you’re sleeping or away from home.
• Batteries require a quality Battery Charger to keep them at a high state of charge. You can have a separate charger, or you can have a combined Inverter/Charger.
• From day-to-day, your backup system will use grid power to stay charged. You can probably get by for a day or two without having a supplemental way to keep your battery charged, but you do have other possibilities. Solar panels are a simple way to provide power to your system in sunny areas, but are much less efficient on cloudy or rainy days. Small wind generators are only useful in mostly windy areas, but have the advantage of providing power at night when solar provides none.
• The last component is optional, and may or may not be available based on the equipment choices you make. It’s an Energy Monitor, and it assembles all of the important information about your backup system such as battery voltage, level of battery charge, current charging or discharging from your battery, and the Voltage and Watts coming from alternate power sources such as solar and wind. I have found the information from my Energy Monitor very helpful in keeping up with what’s happening in my backup system.

The exact manner you will assemble your system will depend on the the items you choose, so follow the instructions for the individual components of your system. That will tell you what wiring and fuses you’ll need to connect up the components.

Lithium vs. AGM vs. Gel-Cell Batteries

You don’t need to become an electrician to make this decision, but it helps to know what you’re buying.

If you’re building your own system from parts, AGM or gel-cell batteries (both mentioned above) are still a solid, affordable choice. They’re sealed, so there’s no risk of the battery leaking or giving off gas, and they’ve been the standard choice for this kind of setup for years.

If you’re buying an all-in-one power station instead, which is the simpler route most people choose and discussed below, you’re very likely getting a lithium battery, whether or not the box makes a big deal about it. That includes the Jackery mentioned earlier in this post. Lithium batteries cost more upfront, but they’re lighter to carry, last years longer before needing to be replaced, and hold up better over time and usage.

If you’re comfortable setting up your own system, AGM or gel-cell will save you money upfront. If you’d rather buy something that works right out of the box, you’re already getting the better battery technology either way with no research required on your end.

The Easier Alternative: Portable Power Station

You may already have what’s commonly called a portable power station. These combinations of a deep-cycle battery, charger, and inverter are packaged together, usually in a plastic case. Better versions of these power stations also have a “Transfer Switch,” which monitors the state of your household power and will immediately switch to the power station’s battery power if the house power fails. And most power stations have some kind of visual screen or indicator lights to help you monitor the amount of power available.

Many people are surprised by everything a power station can run, and that includes timed bursts of power to keep the fridge and freezer at safe temperatures.

Brand names I can recommend are Phoenix (shown, not available on Amazon), Grecell, and Jackery (this is the one Survival Mom owns and uses.)

While an integrated power supply offers a simpler way to ensure your freezer’s power supply, most power stations cannot add more capacity when needed. However, if you choose your power station carefully, with an eye to future expansion, you’ll find there are power stations that can be accessorized with an additional battery and connecting cable or even a “parallel” cable that connects two identical power stations to provide higher-capacity outlets.

Tips for Protecting Your Freezer from Power Loss

• If you have a solar power system for your house with a battery like the Tesla Powerwall, you’re all set, just make sure the battery system covers the electrical outlet that powers your freezer.
• A thermometer is essential for monitoring conditions inside your freezer.
• I also keep a couple of medium-sized styrofoam coolers near my freezer in case I need to leave the house in an emergency. They have enough capacity to take all of my frozen meat, as well as block ice and/or reusable ice blocks.
• If you don’t have a backup power source for your freezer and their is a power loss, wrap it in blankets to insulate it and don’t open if if possible.
• To assess whether your freezer lost power while you are away on vacation, keep a baggie of ice cubes in it. Check them when you return. Solid ice cubes or partially frozen cubes with sharp edges indicate your food likely stayed frozen and is safe to consume. However, completely melted ice cubes suggest your freezer may have been off for an extended period. Unfortunately, some or all of your food may not be safe. In this case, follow the “when in doubt, throw it out” rule to avoid potential foodborne illness. Rounded or melty ice cubes could indicate a partial thaw. Some foods like meats might still be salvageable if refrozen immediately. But proceed with caution!

Testing Your Backup System Before You Need It

A battery backup system you’ve never tested is relying on hopes and dreams. You need to know before a power outage whether or not it actually works.

• Test under real load every few months. Switch to battery power for an hour or two during normal daytime hours and confirm the freezer actually stays cold and the battery holds its charge as expected.
• Check battery terminals for corrosion, especially on a DIY setup, and clean them if you see buildup.
• Verify your transfer switch actually triggers if power drops, rather than assuming it will. This is the most common point of failure.
• Keep your charger topped off, especially heading into storm season, rather than discovering a partially charged battery mid-outage.

A few minutes of testing a couple of times a year beats finding out your system doesn’t work during the outage as you watch your expensive freezer full of meat spoil.

Why You Need a Backup Power Source

Last year, under blue skies and no disaster in sight, my power suddenly went out for 2 ½ days due to a failed underground electric cable. Talk about a real-world exercise of my preparedness! Another time, a rogue tornado hit our town — the last thing I expected but it caused our power to be out for a full day.

Fortunately I had several ways of providing power for both my freezer and refrigerator, and while I had to improvise a few things, I lost no food and kept outside lights on at night for security. If I had not had a way to power the freezer in this period, I would have lost hundreds of dollars worth of food. A battery backup for your chest freezer is inexpensive when compared with the potential loss of your frozen food.

A solar generator might be the best choice for you as a backup power supply. They’re silent, never give off any dangerous fumes, and there’s no need to store fuel. Survival Mom has tested and uses these solar generators from 4Patriots. Read this post for a thorough review of 4Patriots solar generators.

Freezers Aren’t Expensive to Run

The reason why it’s possible to assemble a backup source of power for your freezer is that freezers really don’t use a lot of power. Once the freezer chills things down to the desired temperature, the insulation efficiently keeps the food frozen with just an occasional run of the freezer’s compressor. My freezer is rated to use only $26 in electricity per year, and it cost me less than $200. When operating, it only uses 1.1 amps of power, which is a low level.

The Basics of Generating and Storing Power

If you’re not familiar with electrical things, I suggest you check out my article on generating and storing power, it will make this article make a lot more sense.

At a minimum, you need to understand:

• That power can be stored in a battery for emergency use, but it’s not the same kind of power your freezer will use;
• That it’s easy to convert the battery-stored power into what the freezer needs; and,
• That you can easily calculate the energy you need to keep your freezer going with the formula Watts=Volts x Amps.

How to Size Your Battery Backup System

The post already gives you the formula (Watts = Volts x Amps), so here’s what it looks like with real numbers:

My freezer draws 1.1 amps at 120 volts, which works out to about 132 watts when it’s actively running. But a freezer’s compressor doesn’t run constantly. It cycles on and off to maintain temperature, so real-world average power draw is usually 20-40% of that number over a full day, depending on the ambient temperature and how well-sealed the unit is.

To estimate how long a battery will run your freezer:

1. Find your freezer’s running wattage (check the manufacturer’s label, or estimate using Watts = Volts x Amps)
2. Multiply by roughly 0.3 to estimate average daily draw, accounting for compressor cycling
3. Divide your battery’s capacity (in watt-hours — multiply amp-hours by voltage) by that daily draw estimate

For example, a 100Ah, 12-volt AGM battery holds about 1,200 watt-hours. At an estimated 40 watts average draw for a small chest freezer, that’s roughly 30 hours of runtime, before factoring in any solar or wind recharging during that period. Bigger freezers, or ones sharing a system with other loads like an alarm or a few lights, will need more capacity accordingly.

This is an estimate, not a guarantee. Actual runtime depends on ambient temperature (the temperature inside your house), how often the door opens, and your battery’s true usable capacity, which is often less than its rated capacity once you factor in not fully draining it.

Why Do I Need a Dedicated Freezer?

You probably already have a refrigerator with a freezer in the kitchen, you may even have an old refrigerator in the garage to keep beer and sodas cold. But realistically you can’t keep your day-to-day food and your perishables set aside for preparedness in the same refrigerator, there’s just not enough room in most cases.

There’s also the issue of accidental thawing of food due to the refrigerator door not sealing properly. I’m sure we’ve all had the experience of closing the door and walking away, only to later discover the door cracked open due to catching on something inside. Kids especially can be careless with closing the door.

A separate freezer that is not regularly accessed allows a steady freezing temperature, mine has the thermostat set to “Normal” and keeps the contents right around 0 degrees F. I check it about once a week to make sure it’s working, and then only to add or rotate out meat that’s been around a while and replace it with new stock. This schedule drastically reduces the chance that the door won’t seal properly; also, the horizontal orientation of the door uses the weight of the door itself to help assure a tight seal.

Which Costs Less: DIY Build or Power Station?

Here are some rough numbers for comparison purposes, but pricing changes a lot as technology improves and new brands and models show up on the market.

• DIY battery + inverter + charger setup: Often $200-500 total for a basic setup sized for a single chest freezer, spread out over time since you can buy components individually.
• All-in-one portable power station: For the size capable of running a freezer (2000 watts is a good choice), expect to pay $1000 or so. This 2000 watt Jackery is a reliable brand.

The DIY route is usually cheaper and will get the job done, but it takes more knowledge and time to assemble correctly. A power station costs more per watt-hour of capacity but removes nearly all the technical risk and has the advantage of being a multi-purpose purchase.

FAQ

Related Power Outage Content

• When the Power Goes Out: Generating and Storing Power
• Is a Solar Power Source the Right Backup for You?
• Cook Off-Grid Without Power: How Many Methods Do You Have?
• Solar Generators: Your Key To Power Preparedness

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Final Thoughts

Emergencies can disrupt life, but your freezer, stocked with protein-rich food, can be a powerful ally. Choose one of these methods to create a backup power system, ensuring your frozen food stays safe. With a layered food storage plan, you’ll have peace of mind, knowing your family is prepared for anything. Act now to safeguard your freezer’s role in your disaster plan!