If you are talking about this type of fridge: MT27F-U1 Medium-Sized Powerful Engel Portable Refrigerator Freezer
I have been using one for 7 years, running it in my service van from a 300 amp/hour battery bank with solar battery charging.
It is a fridge/freezer (depending on where you set the thermostat) and is rated at 2.5 amps DC at 100% duty cycle for it's Danfoss compressor. It never runs full time though, as it is very well insulated....perhaps 40-50%. So you are looking at a 1.25 amp per hour draw or 32 amp/hours per 24 hour day.
Not much really, but you certainly would want some type of battery re-charging system available to keep your batteries up.