When discussing how long your
battery will power a fridge it is best to clarify if the fridge is condenser or absorption.
Comparing the two types is like comparing apples and elephants!
For both types the essential factors in deciding how long your batteries will power a fridge are
a)
battery capacity (amp hours)
b) average daily power requirement (watt hours per day) of the fridge.
Max power demand (e.g 250 watts) is irrelevant.