Geoff,

I'll piggy back on what Peter said. The charge rate of your inverters or converters also contributes to determining how long it takes to charge your batteries.

But to address the question of why run the generator, I think it is a matter of preference. I do not rely on auto start. I prefer to maintain a higher charge in my batteries than the auto start is set for so I run the generator often for two reasons. The first is to keep the battery voltage level in excess of 12.3 or 12.4.

But primarily the reason is I want to use all the features of my coach. If I wanted to conserve I would buy a tent. I run my generator in a rest area if we are going to stop for a long lunch. I run my generator in a rest area if we stop for the night from the minute I shut down until I go to bed. I want to run my airs, or my heaters, or every appliance we have on board if I choose and I don't want to "manage energy". If I was spending a week at Quartzite (that ain't never going to happen) I would be conserving energy.