A leisure battery can indeed be used to power a 12V fridge. However, for exactly how long that fridge can be powered will depend on a number of different factors.
It is most simply explained with the following formulas. Which can be used to work out how long any leisure battery will last:
First, find the Total Energy(Wh) of the battery:
- Battery Capacity (Ah) * Battery Voltage(V) = Total Energy (Wh)
You can then work out the hours of use:
- Total Energy(Wh) / Fridge Power Consumption (W) = Hours of Use
Battery Capacity (Ah) is the amp-hour. This is the amount of charge that the battery can deliver over a certain period of time.
Battery Voltage (V) is the voltage rating. This is the amount of electrical potential that the battery has.
Total Energy (Wh) is the total amount of energy, which is the product of the battery capacity and voltage shown above.
Fridge Power Consumption (W) is the amount of power that the fridge consumes in watts.
Hours of Use is the total amount of time that the fridge can run on the battery before the battery is drained.
Example: if you have a 1000 Ah leisure battery with a voltage rating of 12 V, the total energy that the battery can deliver is 12000 Wh (1000 Ah * 12 V). If your fridge consumes 50 W of power, then the battery can power the fridge for approximately 240 hours (12000 Wh / 50 W = 240 hours).
There are several factors that will impact how long a 12V fridge can run on a leisure battery. Firstly, the size of the battery is important here. The same is true for the fridge’s volume in litres or quarts. The bigger the fridge’s volume, the more it will take to power it. The same is true of the thermostat setting on the fridge too. The ideal setting is said to be anywhere below 37°F (3°C) and 40°F (5°C). If the temperature goes above or below this, the fridge, and therefore the battery, has to work harder. This will then impact on how long the fridge can be powered by the battery.
Room temperature also has an effect on a fridge and, therefore, how long it can be powered by a battery. When the ambient temperature of a room (or the outside ambience if the fridge is outdoors) becomes too low, the fridge uses more energy to bring the refrigerant, a chemical used in the cooling mechanism, to a boil and create a vapour. When the ambient temperature of a room is very high, the fridge’s condenser cannot cool down properly and causes it to function inefficiently, impacting on battery life.
The frequency with which the fridge door is opened and for how long will also have an impact on how long it can be powered by a leisure battery. When it is open, the fridge has to work harder, particularly if it is left open for longer periods of time.
The battery chemistry, whether lead acid, lithium ion as in a solar generator and lithium iron phosphate or LiFEP04 within the battery will also impact running time. Batteries which contain lithium iron phosphate usually have a lifespan that is two to four times longer than a lithium-ion battery. A lithium iron phosphate battery usually has a cycle life of around 5,000 times.
The final factor affecting the length of time for which a 12V fridge can run off a leisure battery is the operating amps of the fridge’s compressor motor. The higher the amperage required by the motor, the more battery energy is used.
Overall, there are many different factors which will determine how long a fridge will run off a leisure battery, although there is no question that running it this way is perfectly possible. As a general example, if you have at least a 12-voltage battery with a rating of around 100 amp hours on hand, the 12V battery will be able to deliver approximately five amps every hour for about 20 to 50 hours before it is fully depleted. Of course, these figures will vary depending on the factors detailed above.