Seems to be. Mine ran for a couple of days last week after driving home, uphill, in mid-90's afternoon heat. I didn't think the ESS would be so well insulated or thermally massive that it would stay that warm for that long, but it kept humming. Next time I took the car to work (and a standard charge), upon returning home I gave it about an hour's charge at 240v, 24A, in RANGE mode, then stopped it. The end result was a pack with slightly less than a full STANDARD mode charge, and because the Range charge puts priority on cooling the pack first, when I unplugged everything, the pump turned off too. Yea!