How Long Will 50ah Battery Run A Fridge?

Wondering how long will 50ah battery run a fridge? Recently i tested my 100ah lithium battery runtime on my 12v mini RV fridge. Based on my findings,

a 12v 50ah lithium battery will run a 12v mini RV fridge for about 50 hours. And a 50ah lead-acid or AGM battery will run the same size fridge for about 20 hours, because of its 50% depth of discharge.

Turns out, my fridge consumed about 1 amp-hour (hourly). Your mileage will vary depending on the size and type of your fridge, battery type, and ambient temperature.

Calculating 50ah Battery Runtime on Fridge

50ah battery runtime on fridge

Here's a simple formula you can use to calculate how long a 50Ah battery will run a fridge:

Formula: Battery runtime = (Battery Ah × Battery volts × discharge efficiency × DoD limit × inverter efficiency) ÷ Fridge power consumption per hour after considering duty cycles

Let's break down each component of the formula:

  • DoD limit: It refers to how much energy can be used from a rechargeable battery before it needs to be recharged again. Lead-acid and AGM batteries can only be discharged at 50% but lithium batteries can be discharged at 100%. Check your battery's user manual guide for more accurate information.
  • Inverter efficiency: Most inverters are about 90-95% efficient. Check the user manual guide for more accurate information.
  • Discharge efficiency: Based on data: Lead-acid battery's discharge efficiency ≈ 80 − 85%. Lithium-ion battery's discharge efficiency ≈ 90 − 95%

Let's suppose you have a 3 (cu. ft.) RV fridge that consumes about 50 AC watts per hour after duty cycles. 12v 50ah lead acid battery, and a 90% efficient inverter.

(50ah × 12v × 85% × 50% × 90%) ÷ 50 watt
(229.5) ÷ 50 watt = 4.5 hours

Easy solution --- Use our battery runtime calculator, and enter the battery specs and the power consumption of your fridge to get the result.

How many watts does a refrigerator use?

First, let's differentiate between watts and watt-hours (Wh).

  • Watts measures how fast energy is being used, like how many watts a fridge is consuming when running.
  • Watt-hours measure how much energy was used over time, like how much energy has been consumed over an hour or a specific period of time.

The power consumption of a refrigerator can vary depending on its size, age, and energy efficiency rating.

To find out how many watts your refrigerator is consuming, you can use a device called a watt meter. This device plugs into a wall socket or into an inverter socket. Then plug your refrigerator into the watt meter. The watt meter will display how many watts your refrigerator is consuming at any given time. As well as the total power consumption over a certain period of time.

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Or, you can check the label or user manual of your refrigerator to see its rated power consumption. The label should show the refrigerator's energy efficiency rating, which will give you an idea of how much energy it consumes on average.

But, if the rated wattage consumption of your fridge is mentioned in watts, for instant 100 watts. in actuality, it will consume 33 watts-hours in an hour.

Because the fridge won't run the whole time, the compressor will stop working when it reaches the set temperature called duty cycle. A rule of thumb is that a fridge will run for about 20 minutes per hour.

Here's a table with some examples of RV refrigerator sizes and their power consumption:

RV Refrigerator SizeWattage Consumption When RunningTotal Power Consumption After Duty Cycle (Hourly)
2.5 cu. ft.120 watts40 watts
3 cu. ft.150 watts50 watts
4 cu. ft.180 watts60 watts
5 cu. ft.250 watts80 watts

Note: These are estimates, to find out the exact value, use the above-mentioned methods.

what affects how long a 50ah battery will run a fridge?

how long a 50ah battery will run a fridge?

When it comes to powering a fridge with a battery, there are several factors that can affect the runtime. Let's break it down in simple terms:

1. The amount of power the fridge consumes will impact the battery runtime. So, the higher the power consumption, the shorter the runtime.

2. The age and condition of the battery can also make a difference. An old or damaged battery may not hold as much charge, reducing its runtime.

3. The environment also matters. The environment also plays a crucial role as the temperature can affect the battery's performance. Higher temperatures can reduce the battery's runtime, while lower temperatures can improve it.

4. Your fridge type. 12v DC fridge will last longer than a same-size AC input power consumption fridge. Because batteries deliver DC power, you need an inverter to convert DC into AC. Inverters are mostly 90-95% efficient.

5. How often the fridge is opened and closed can impact the runtime too. The more frequently the fridge is used, the more energy it will use and the shorter the battery runtime will be.

So, keep in mind these factors when determining the expected runtime of a battery-powered fridge. And, make sure to properly maintain both the battery and fridge to optimize their performance.

Related post: Battery Charge And Discharge Rate Calculator

50ah battery vs fridge --- Tips for Extending Battery Runtime and Health

Here are some tips to help you get the most out of your battery:

  • Choose a more efficient fridge: As we mentioned earlier, the size and efficiency of your fridge will affect how long the battery will last. Choosing a smaller, more efficient fridge with a higher COP can significantly extend your battery's runtime.
  • Keep the fridge full: A full fridge will retain its temperature better than an empty one. Try to pack your fridge as full as possible to reduce the amount of time the compressor needs to run.
  • Keep the battery charged: Keeping your battery fully charged will help extend its lifespan and ensure you get the maximum runtime. If you're using a solar panel to charge your battery, make sure it's positioned in a sunny area to maximize the charge.
  • Use a battery monitor: A battery monitor can help you keep track of your battery's charge level and ensure you don't over-discharge it. This can help extend the lifespan of your battery and prevent damage.
  • Use a battery with a higher capacity: If you need longer runtime, consider upgrading to a battery with a higher capacity. A 100Ah battery will last twice as long as a 50Ah battery, all other things being equal.

How long will a 50ah battery run a fridge?

Here's a chart showing how long will 50ah battery run on different sizes of fridges.

RV Refrigerator SizeTotal Power Consumption After Duty Cycle (Hourly)50ah Battery Runtime (lead-acid)50ah Battery Runtime (Lithium)
2.5 cu. ft.40 watts6 hours14 hours
3 cu. ft.50 watts5 hours11 hours
4 cu. ft.60 watts4 hours10 hours
5 cu. ft.80 watts3 hours7 hours


How long will a 50Ah battery run a small fridge?

A 50Ah battery will run a small fridge for about 30-50 hours, depending on the fridge's efficiency, battery type, and ambient temperature.

Can I use a car battery to power my camping fridge?

Yes, you can use a car battery to power your camping fridge, but it's not recommended. Car batteries are not designed for deep cycling and can be damaged if discharged too much.

How do I know if my battery is fully charged?

You can use a battery monitor or voltmeter to check your battery's charge level. A fully charged 12V battery should read around 12.7 volts.

What is the best type of battery for powering a camping fridge?

Lithium-ion batteries are the best type of battery for powering camping because of their high discharge efficiency. Also, lithium batteries can be discharged 100%.

Bottom line

In conclusion, a 50Ah battery will only run a fridge between 10-50 hours. You can extend its runtime by choosing a more efficient fridge, keeping the fridge full, keeping the battery charged, using a battery monitor, and upgrading to a higher-capacity battery. 

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I travel around the world in my RV and document my journey on YouTube. I also cover general off-grid and minimalism practices to help you thrive in any tiny living or off-grid situation.

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