Low voltage auto engine start for 75 bucks, who has one?

Now that I have some time on this system, the ac unit keeps truck cold in all but extreme heat ( I was in 107 lasvegas sun sitting during the day in asphalt parking lot) I fired up the truck to augment the ac and allowed it to idle until dusk, when even though it was still 100 outside, the through the wall ac could keep up.

It will run about 3 hrs nonstop off just the 4 batteries or 7hrs if temp outside is 85 or less at night and not drop the voltage below 12.3. I've wired the generator to automatically fire up and charge batteries when drops below the 12.4v threshold.

I'm very pleased with the setup so far.