Any supplemental A/C will take a toll on the house battery reserve. On shore power my Starcool works ok but not like I want it to. Nature of the beast I'm told. Owners of the new Danhard report it works well on shore power. Also the Danhard needs the correct sized inverter to run it off a battery. Larger inverters generally use a slight bit more power in a standby mode than smaller units but the physical size and price is usually more of an issue. But no matter what, running the air off the battery system alone will deplete it within a few hours and heavy loads can shorten the batteries life. Of course how long it can run depends on how large the house battery system is. This is why most use a generator or shore power to operate the A/C. You will need a 30 amp shore power supply and the correct size extension cord to hook up your van when using the A/C but most campgrounds and trailer parks supply 30 amp or larger service.
2006 Ford 6.0PSD EB-50/E-PH SMB 4X4 Rock Crawler Trailer
If you're looking to keep an animal safe in the van while you're away, the Chilly Dog turns on the van at a temperature threshold you set, so the engine runs the AC. You can also set it to turn the van on periodically.