Powering a 12V Fridge or Freezer From a Battery | What you need to know

If you’re going outdoors for a weekend camping trip and have a portable 12V fridge or freezer with you, or perhaps you plan to run a 12V mini fridge in your remote cabin/garage then you may want to know what battery size (Ah) to use.

This is because some 12V fridges do not come with inbuilt batteries already so selecting one in a sea of many options can be a challenge!

With this post, you’ll be able to:

select what battery size (Ah) to use for your 12V fridge running reliably and how long it can run while keeping your food and drinks fresh whether traveling, at home, or out camping.

What Size of Battery (Ah) to Run a 12V fridge?

There’s no one right or specific battery capacity (Ah) that is suited to run a 12V fridge.

The most suitable battery capacity depends on:

  • the fridge’s average power consumption (watts), and
  • how long (hours) you plan to run before you charge the battery again

Using an AGM Battery

That said, as a rough guide, a fully charged 100 Ah AGM battery will power a 45-watt portable fridge, about 37-45 quart capacity for about 8-12 hours before it is drained to the recommended depth of discharge of 50%.

Using a LiFeP04 Battery

With a LiFeP04 battery, a 50Ah or 600 Wh capacity will power the same 45-watt portable fridge for about 8-12 hours before it is drained to 80% of its capacity.

Using a Car Starter battery

You can also power the portable fridge off the car starter battery by plugging one end of the fridge’s DC power cord into the fridge’s 12V port and the other end into the car’s cigarette lighter port.

The current draw of a 45-watt portable fridge at 12V is about 4 amps only and is therefore within the limits of many cigarette lighter ports that are usually designed to handle either 10 amps or 15 amps.

Make sure you confirm the current rating by referring to the car owner’s manual.

Keep the car engine running to guard against deeply draining the car battery.

Using the Leisure battery

Instead of connecting the portable fridge to the car starter battery, you can connect it to the leisure battery.

This mitigates the risk of deeply discharging the car starter battery so that you are unable to start the car!

Note: Some portable fridges support both 12V and 24V battery voltages. Confirm whether your fridge is one of them.

Using a Portable Solar Generator

You can also connect the portable fridge to a portable solar generator instead of a car starter or leisure battery.

Here are indicative runtimes you can expect for selected portable solar generator capacities.

Portable solar generator – Battery capacity 240 Wh

The indicative runtime of a 45-watt fridge is between 7- 10 hours assuming a duty cycle of 50%.

Portable solar generator – Battery capacity 716 Wh

The indicative runtime of a 45-watt fridge is between 22- 30 hours assuming a duty cycle of 50%.

Extending the Runtime of your Portable Fridge on Battery

You can use one or a combination of the strategies below to extend how many hours your fridge will run with a given battery capacity.

  • Set the cooling mode to ECO. Many 12V fridges have an eco mode that uses less power.
  • Connect the fridge to a battery directly instead of supplying AC power from an inverter connected to a battery. You can lose as much as 15% of the power during the conversion of battery power to AC power!
  • Precooling food and drinks before putting them in the fridge to lower the fridge’s energy consumption
  • Also, keep the fridge in a shade to keep its power consumption at a minimum

Connecting the fridge directly to a 12V or 24V battery bank instead of a DC to AC inverter connected to a battery minimizes power losses and can extend the fridge’s runtime on battery.

How Many Batteries for a 12V Fridge?

Again there’s no one answer. There are several battery configurations available and what is presented here is only a guide and by no means exhaustive.

One approach to consider is to start with the suitable capacity for your fridge and from there the number of batteries to attain that capacity.

As an example, you can connect 2 x 50 Ah AGM batteries in parallel or 1 x 100 Ah AGM battery to provide about 8-12 hours of runtime for a 45-watt portable fridge.

Connecting a larger battery bank will provide a longer runtime.

The Power Consumption of a 12V Compressor Fridge

This depends on the capacity (quart/liters), and design.

As an example, a 54 quart/50-liter 12V compressor fridge consumes about 40-60 watts of power.

In general, larger capacity (quart/liter) or less efficient fridges consume more power than the smaller capacity and more efficient designs.

Always refer to the owner manual of the fridge for its actual power consumption (watts).

The Amp Draw of a 12V Fridge

This can vary from one fridge model to another. As a rough guide though, a 54 quart/50l may draw about 5 amps (60W) at 12V at startup and about 3.3 amps (40 watts) when running continuously from a 12V battery.

24V battery

When connected to a 24V battery bank, a 54 quart/50l may draw about 2.5 amps (60W) and about 1.65 amps (40 watts) when running continuously.

Always refer to the owner manual for your specific fridge model.

Related Questions

1. What Size of Solar Panel to Run a 12V Fridge or Freezer?

Does the 12V fridge have an inbuilt battery? Confirm the manufacturer’s recommendation on what solar panel capacity to use.

Make sure the solar panel has the recommended connector type to plug into the portable fridge.

Otherwise, I recommend that you use a 100-150 watt solar panel or larger to keep a 100Ah AGM or 50Ah LiFePO4 battery that can run a 45-watt portable fridge for about 8-12 hours.

This assumes that your location receives an average of 4 hours of sunshine each day.

Closing Thoughts

You can get about 8-12 hours of runtime using a 100 Ah AGM battery when connected to a 12V 50 liter/54-quart fridge with an estimated power consumption of 45 watts.

With a LiFeP04 battery, a 50Ah or 600 Wh capacity will power the same 45-watt portable fridge for about 8-12 hours before it is drained to 80% of its capacity.

Related Topics

Leave a Comment