The length of time a 12V fridge will run on a battery depends on the fridge’s power draw and the battery’s capacity. For instance, a fridge using 1 amp per hour could operate for approximately 85-100 hours on a fully charged 100AH battery. Factors like outdoor temperature, how often the fridge is opened, and the efficiency of the unit will impact this. You can extend the battery life by using solar panels or charging the battery while driving.