Great post Phil. The one time I had to use the idle option was not for battery charging but to run the dash AC. We were trapped in a tiny RV park notched out of the cornfields of southern Illinois in mid June.. Tornado warnings were up, the temp was 100 with matching humidity. The roof air struggled to get the temp down to the high 80's and the humidity was miserable.
I let the V -10 idle and fired up the dash air with our windshield cover in place. It was still warm and humid but far more comfortable. I let the dash AC run for about 90 minutes after which the roof air seemed better able to deal with the heat. Just another option/difference between a coach with a large gasser vs the MB diesels... just sayin.
\When we checked into the park to just get off the road and hide out until the storms passed they explained their shelter situation... Down the road in either direction were a couple of farms that had large basement shelters. They urged us to immediately flee to one or other if the sirens went off. It was a long night but by morning the skies had cleared and we continued on to Missouri and Arkansas before returning to Tucson. This was our third, but not our last close call with tornados on that 2 month cross country trip.
Here is another shot from our site at Hawley Lake where my bride captured a nice sunset:
