Yeah, I see completely issues on it. That’s why I like that one camper you did try that have the mini air-con within it, which does last nearly the whole day by 16 hours on two lithium battery. And with a portable battery, it help out with bit of work too and minor cooking. Which is probably why I like it with the air-con, since it helps with the heat. As for the test try on the one you bought, not worth the money you spent on.
Really interesting, I will look into using something like that in my small caravan. I think you need to separate the in and out hoses a bit more as I think it's sucking in the hot air from the outlet which will reduce it's effectiveness. Love your adventures, keep having fun with your van.