Hi Mark,
The great thing is you have plenty of battery power and solar. We have 160w solar and only 100amp hour of battery so we struggle, plus our Waeco fridge draws 6 amps when the compressor is running. In cool September weather with sunshine we could probably run indefinitely - and your additional battery power and solar puts you ahead of us.
Re. ferries - if you have a 24 hour ferry trip then you might need to plan your battery usage.
I suspect you already have a good battery meter to show how much charge remains. If not already supplied with the fridge I would look at getting an after-market digital thermometer so you can see the temperature of the fridge without opening the door. The combination of the two means you can plan ahead in situations where the truck won't be running and you won't have sufficient power from solar. You can also work out what the numbers on the fridge thermostat actually translate to in Celcius.
One trick we use if we know we will be struggling to have enough solar, hook-up or alternator power to recharge the batteries over several days is to turn the fridge up and get its temperature really low in advance, then once we are running on battery, the first time we go into the fridge, turn it down - that way it may not need to run for hours thus saving battery power.
The other thing we did is work out why we were opening the fridge a lot (and therefore wasting cold air) - firstly to check the temperature - an external temperature gauge fixed that, and secondly to get milk - so now when we get to a campground Sally fills a cup with milk and leaves it on the side for tea and coffee - so no need to keep dipping into the fridge for that.
After renting that class C for a week with an absorption fridge and remembering how intolerant it is to angle and how slow it is to adjust, I've been looking more favourably on my own compressor fridge.
Steve.
