Angel,
I am looking to have an Isotherm built in and am figuring this out as well..
"4.7 Operation with converter
As an option, the refrigerators can be equipped with
an converter which operates on the mains power. It
can be mounted direct on the back of the refrigerator
or separately besides the refrigerator. The converter
will feed the power for the compressor direct from the
mains as long as this is available, and automatically
switch over to battery power when no mains power
is available. The converter must be connected to the
mains with an earthed power plug."
See
http://www.isotherm.com/prodpdf/1361/2/ManCruise.pdf
It seems this converter, which install on the back of the refrigerator itself will automatically switch to AC when on shore power and ASU would be disabled as a result, then automatically go back to 12V when shore power is discontinued.
Who ever figures out an ideal system, let me know. I still am deciding if a drawer system would be more functional. However "CR 42 and CR INOX cannot be equipped with ASU." per that .pdf file. Not sure why this is....maybe AC/Inverter makes it non-compatable. Anyone have an answer with this?
-John.