The runtime of a 12V fridge on a battery depends on the fridge’s power consumption and the capacity of the battery. For example, a fridge that draws 1 amp per hour could run for about 85-100 hours on a fully charged 100AH battery. However, this can vary based on ambient temperatures, fridge efficiency, and how often the fridge is opened. Adding solar panels or charging the battery while driving can help extend the runtime significantly.