I have a 120 Amp Battery how long can I run my fridge for?

This depends on numerous factors..

It depends on how hot the environment is and how often the fridge is opened and if the fridge is insulated or not.

               The hotter it is the more power it will need to keep things cool.

               If you have an insulating cover this helps keep the fridge cooler

               The more you open it the more it will need to cool down again.

But here are some approximate values you can work with:

Lets use an example a 40W average consumption fridge (CRX50)

This will draw about 3.3Amp on 12V per hour. (40W Div by 12V = 3.3Amp)

If you have a 120 Amp Hour battery this means you will have 36 Hours maximum operation (120 Div 3.3).

If you only wanted to drain about half of the battery - then this is about 17 hours.

Again these are basic approximate figures, each fridge, installation, amount of use will all change the final outcome.