temporary loss of 12volt power when turning off lights.

WDE wrote:
I camp with the coach battery disconnected (not charging) and running the 12 volt system off the converter.

There is absolutely, positively NO reason to do that; none, nada.

In fact, it probably means that your batteries are partially discharged most of the time and it's hard on them too.

Not having a fairly constant load on the converter/charger might have been hard on it too. It wasn't intended to work that way.

And yes I know you've been doing that for a thousand years; still doesn't make it right.