Minimum current draw of AC to DC converter at no load
From the 'Inteli-Power Specifications Table' on the link you gave, I see that the no-load voltage is given to be nearly 13.6V, and guaranteed to be over 12.6V under full load. Clearly current will not be constant if you are changing the load; voltage on the other hand will be compensated for under a wide range of current draws. The unit will surely draw power even under no-load. It appears that there is no minimum current draw. I have heard, however, when going the opposite way (DC/AC converter) that some inverters will shut off under no load condition. Having no access to a schematic or the code running this thing, I can't say for certain, but it looks like it will work just fine under no-load conditions.