Originally Posted by Soppy
You should be able to easily install a 12v fridge. Most 12v fridges will draw around 5 amps running current. Your existing wiring should be able to handle the current without much voltage drop if it is #12 wire. #14 will work if the distance from the battery bank is not to far. You will have no problem running the fridge while travelling and a 100ah battery should be enough to power the fridge for 24 hrs. Of course this will depend on the air temperature and actual fridge. You should also upgrade your converter with a newer model with multistage charging. You may also consider changing to Lithium batteries.
I am guessing you did not do extensive research on those numbers, but they seem low to me !
Background : A 12V compressor refrigerator takes the DC voltage bumps it up "some" and converts it to 3 phase. (3 phase motors are much more efficient.). This is all invisible to the consumer (black box mounted near the motor/compressor).
Follow manufacturers guide lines on wire size (you will likely have to install new wire from the battery to the refrigerator). The big issue is the type and size of the battery bank and how you are going to charge it.
Your old converter is likely not up to the job. It would likely have to be replaced. This would be a good time to consider an inverter/charger/automatic transfer switch.
Batteries type/size depends on your budget. Lead Acid (GC2) are adequate, if you have the space. Boondocking might require 4, or at least a small generator/DC-DC charger. LiFePO4 are expensive, but lighter and store more energy.