If you have enough solar preferably 240watts upwards you can drive your fridge on sunny days without drawing from the battery capacity at all.
I chose to utilise a CBE CSB2 to control the on/off as this will turn on at 13.6 volts and stay on until the batteries drop to 12.5 volts.In this case the 12.5 volts will be when the batteries are under load which is no draw at all as switching off will immediately take them back beyond 12.6 which is fully charged.
Although my fridge is a later 8 series model with an S+ as well as a D+ signal input it does not help me as these only operate the inbuilt relay on the fridge and will not operate the fridge relay in the CBE distribution panel (this requires a D+ signal, i.e engine running)
One way around this would be to feed the fridge direct from the batteries and let the fridge control it.
My preference was to ignore the S+ & D+ at the fridge and instead trick the CBE panel into believing the engine is running.
This has been done by Martin "Funflair" and I have adopted the diode method from him but the on/off by my idea of the CSB2
So we first find the ignition signal at the distribution board and CUT it, fit a diode and splice and extra wire off that that will connect to the red wire of the CSB2[You must be registered and logged in to see this image.][You must be registered and logged in to see this image.]
Here is the wire (white with red plug) spliced and looped back out through the bottom of the board[You must be registered and logged in to see this image.]
Now 12 volts from the CSB2 will be sent to the D+ once 13.6 volts is sensed.
Here it is the one top right and it gets the voltage from my solar batteries via the 12 volt box beneath.
I have this week rearranged and improved the layout of my kit too.[You must be registered and logged in to see this image.]
With a poor sky the batteries hang on for some time at around 12.7 but heavy cloud will drop it to 12.5 and the fridge will auto change to gas.
With a clear sky my solars knock out enough for the 14 amps MAX of the fridge and spare for the 6 batteries across the van through other overflow relays[You must be registered and logged in to see this image.]
The evidence so far is that my fridge cools every bit as good on 12 volts as gas or mains.
The beauty is that I'm only running off my solar batteries that feed my inverter and not my habitation batteries although if it was the 12.5 volt cut off would prevent them being drained at all.
The only drawback is that once the D+ is tricked then anything esle that acts on the D+ signal will be affected.
Fortunately I don't have an electric step nor a satellite dish.
My electric awning should still work as when I switch the inverter on it should drop the voltage to 12.5 and disconnect D+
I have also fitted a switch on the side of the 12 volt socket box that will isolate the function when not required.