You can pretty much forget that if you will be camping for any length of
time.  To verify this, check the power rating of the fridge and compare it
to an aux battery (amp rating X 12V = Power).  I don't even think you can
keep up with a solar cell too.

That is why folks use a 3 way fridge (12V, 120V, Propane)

Rob

http://msnhomepages.talkcity.com/PassportPl/gunter01/