Several factors influence how long an RV fridge will run on battery power.
Below you’ll learn how to get a quick estimation (good enough for most cases) and how to calculate exactly how long your RV fridge will run on battery step-by-step.
How Long Will Your RV Fridge Run on Battery Power?
A 12V DC absorption fridge rated at 15A, powered by a 100AH lead-acid battery, will run for approximately 3 hours and 20 minutes before it is depleted below the 50% threshold (assuming it’s the only appliance using power).
That’s just one very specific example. Your RV fridge and battery setup will undoubtedly be different.
So, let’s learn how to quickly calculate how long your fridge will run on battery power. We’ll need to start by gathering the fridge’s energy consumption and the power rating of the battery(s).
1. RV Fridge Energy Consumption
The type of fridge plays a significant role in how long it can run on battery power.
|Type of Fridge||Watts (W)||Amps (A)|
|12V DC Absorption Fridge||175-275W||15-20A|
|120V AC Absorption Fridge||300-600W||2.5-5A|
|12V DC Compressor Fridge||60-180W||5-14A|
Please note that these ranges are illustrative and may vary based on the specific make and model of the fridge. Always refer to the manufacturer’s specifications for accurate energy consumption details for your particular fridge.
Tip: Look inside the refrigerator for an information sticker that shows the power draw in watts and amps. Alternatively, you can look in the owner’s manual or do a quick search online for your make and model.
Once you know the energy consumption of your fridge, we need to figure out how big your power supply is.
2. Battery Capacity
The battery capacity tells you how much energy the battery can store. This capacity is measured in ampere-hours (AH). Think of it like a big water tank; the more AH, the more energy it can hold. Here’s what you need to know:
- Lead-Acid Battery: These are commonly found in RVs due to their lower price point. But you can only use about half of their capacity. If a lead-acid battery is rated at 100AH, you should only use 50AH before recharging it. Using more might damage the battery.
- Lithium Battery: Unlike lead-acid batteries, lithium batteries allow you to use almost all of their capacity. If it’s rated at 100AH, you can use close to that amount. They are usually more expensive but provide more usable energy.
- Multiple Battery Systems: If you have more than one battery, you can add their capacities together. If you have two 100AH lead-acid batteries, you’ll have a total of 100AH usable capacity (50AH from each).
Important: Just like people, batteries deteriorate as they get older. An older battery might not provide as much energy as it did when it was new.
You can usually find your battery capacity rating on the battery itself.
3. Calculate How Long Your Fridge Will Run
Calculating how long your fridge will run on battery power is as simple as dividing the usable energy from your battery by your fridge’s energy consumption.
Usable Battery AH ÷ Fridge Amps = Time
- Battery: 100AH lead-acid (50AH usable)
- Fridge Consumption: 5A
- Calculation: 50 ÷ 5 = 10 hours
In this example, the fridge will run for roughly 10 hours on battery power.
Hate math? Simply plug in your usable battery AH and fridge amps into the calculator below.
RV Fridge Runtime Calculator
Additional Factors That Affect How Long Your Fridge Will Run
Calculating how long your fridge will run on battery power isn’t just about the battery and the fridge’s energy consumption. Several other factors can influence the actual runtime, including:
- Outside Temperature: The hotter it is outside, the harder your fridge has to work to keep things cold. This means it might use more energy, reducing the runtime.
- Opening and Closing the Door: Every time you open the fridge door, some cold air escapes, and the fridge has to use more energy to cool down again. Frequent opening and closing can reduce how long the fridge will run on the battery.
- Other Appliances: If other devices use the same battery, they will also consume energy. This means there might be less energy available for the fridge, reducing its runtime.
- Fridge Settings: If you set your fridge to a colder temperature, it will use more energy to maintain that temperature. This can also affect how long it will run on the battery.
- Battery Maintenance: Proper care and maintenance of your battery can ensure it provides the expected amount of energy. Neglecting maintenance might reduce the battery’s capacity over time.
- Solar Charging: If you have solar panels charging the battery, the amount of sunlight and the panels’ efficiency can affect how much energy is available for the fridge.
- Inverter Efficiency: If you’re using an inverter to convert the battery’s power to the type your fridge needs, the efficiency of the inverter can also affect the runtime.
Calculating Exactly How Long Your RV Fridge Will Run
Estimating how long your fridge will run on battery power alone is helpful and is really what most RVers are looking for.
But if you want a more exact number, it’s time to get a little more scientific. By conducting a controlled experiment, you can gauge exactly how long the fridge will run until the batteries are depleted.
What You’ll Need:
Here’s a step-by-step guide to running the test:
- Charge the Batteries: Use shore power to bring the house batteries to a full charge.
- Set the Refrigerator Temperature: Adjust the refrigerator’s temperature to 34°F (1°C) to simulate typical usage.
- Disconnect Shore Power: Unplug from shore power to switch to battery mode.
- Record Battery Data: Begin recording hourly battery voltage and state of charge readings with a battery monitor. This will provide a detailed understanding of how the battery performs over time.
- Monitor Refrigerator Temperatures: Optionally, you can also record hourly refrigerator temperatures to assess how well the fridge maintains the desired temperature.
Important: If your RV has lead-acid batteries, you should only discharge it to about 50% before having to recharge it. Otherwise, you will cut its life short.
By following these steps, you can obtain a realistic assessment of how long your RV fridge will run on battery power. This hands-on approach takes into account the unique characteristics of your RV’s battery system, fridge type, and a few other variables, providing a more tailored insight.