hi again, I might have found the answer myself but would welcome thoughts or confirmation; this fridge is not going to function from the inverter supply off the leisure battery. If not on mains elec, it will work only while the engine is running and generating enough power. In other words, when stopped/camping unhooked, treat it as a passive cold box (no elec supply – using cold packs).
build you own campervan and live the van life