A refrigerator is one of the most essential appliances in a home that needs to be running throughout. With refrigerators, you don’t have the option of leaving it off; unless you don’t have any food in it.

A 200 Ah battery offers a  great backup solution for off-grid homes. But how long will it run a refrigerator?

A 12v 200 Ah  Lithium-ion battery can run a 200-watt refrigerator for up to 10 hours a day while a 24v 200Ah lithium battery can run up to 20 hours. With the addition of a solar panel, you can run the refrigerator for up to 24 hours.

Let’s take a look at how you can size your system:

What does 200 Amp-Hour Mean 

Amp-hour rating in batteries gives the charge in amps that can be drawn from a battery over a certain time given in hours.

Amp-Hour) rating of a battery can also be calculated by multiplying the rated capacity by its terminal voltage. But this does not represent the real-world performance of batteries.

A Deep Cycle Battery battery is intended to produce the charge for a long period of time like 20 hours. So for a 200 Ah battery, it should produce at least 10 amps over a 20-hour period. 

However, you can go higher or lower depending on the appliance you are using.  Deep cycle batteries are recommended to be discharged at 20% of their capacity so for a 200 Ah battery the max discharge per hour would be 40 amps meaning it can last 5 hours.

For lead acid batteries, this can be lower as they can only be discharged up to half their capacity meaning it’s only 100Ah of their capacity that is usable. This means it can last only  2.5 hours when discharged at 40 amps and 5 hours at 20 amps and 10 hours at 10 amps.

How Long Will a 200 Ah Batter Last with a 200W Refrigerator

In order to calculate how long a battery will last with an appliance, we first need to consider the wattage of the refrigerator. Most modern refrigerators are rated at 200 watts. This figure is the running wattage of the refrigerator. The starting wattage can be 200-400 watts higher than this.

The starting wattage (power required for the compressor to turn ON and run) is twice the operating wattage of refrigerators. Smaller capacity refrigerators use around 200-300 watts, whereas bigger ones use 500-650 watts.

Basically running a refrigerator comprises the compressor cooling the refrigerator and freezer for 6-8 hours. The defrost cycle turns the heating coils on for about 30 mins every 24 hours. This is all dependent on the brand, model, and size of the refrigerator.

You’ll need to convert this into amps;

Amps = Watts/Voltage

So for 200 Watts, the refrigerator will be drawing;

200/12 = 16.67 amps

For the defrost cycle it needs 600 watts however since it only lasts for 30 mins you half the wattage requirement:

300/12  =  25 amps

So the refrigerator will use a total of 40 amps when running and using the defrost cycle and 16 amps when running normally.  This, therefore, gives you a total of 10 hours of running time when using a 200 Ah 12v battery.  If you use a lead-acid battery it can be less up to only 5 hours if your addon to the conversions losses best it will do is 4.5 hours.

If you were to use a 24V battery system and inverter it will have less draw on your system because of the higher voltage;

So for 200 Watts, the refrigerator will be drawing;

200/24= 8 amps

For the defrost cycle;

300/24  =  12.5 amps

For a 24-volt system, the battery performance is better as the amps drawn are halved. This means that it will only draw 20 amps in the first hour and 8 amps continuously giving you double the time.

This, therefore, gives you a total of 20 hours of running time when using a 200 Ah 24v lithium battery.  If you use a lead-acid battery it can take you up to  10 hours.

How many watts is a 200 Ah Battery 

You can use the following formula to determine how many watts can be drawn from a battery.

Watts = Volts x Amps

So if your battery is 12v and has a 200 Ah capacity, then you can draw 2400 Watts from it. This is for the whole lifecycle of the battery. With a 40 amps draw this means you have a max draw of 480 Watts.

For a lead acid battery you can only discharge up to 50% so you only want to draw 1200 Watts (1/2 of 2400 Watts) then you will need to discharge the battery over 20 hours which will give you 60 watts per hour.

For our refrigerator, you can use the same calculation using the watt-hours.

A reminder that this wattage is supplied through an Inverter and not directly through the battery. You’ll need to match the running wattage of the refrigerator with the inverter. The inverter also needs an adequate rating for the start-up wattage of the refrigerator so it should be at least 600 watts.

200 Watts  x 6 Hours =  1200 Wh

Let’s add the defrost cycle for around 30 mins

600 Watts x 0.5 hours = 30 Wh

So the total power required to run a fridge in 6 hours will be

1200 + 30 = 1230 Wh

For 12 hours you’ll need 2460Wh and for 24 hours you’ll need 4920 Watt-hours.

That’s 5 kWh of electricity each day.

So you come to the same conclusion that the 12v 200Ah battery can run the 200 Watt refrigerator in around 10 hours and 20 hours for a 24v 200Ah lithium battery.