As I see it, the relay setup is just a switch that's in automatic.  What
you're talking about is also just a switch but only with a manual mode.
Having the ability to use battery #1 or battery #2 or both has its
advantages.  The downside is having to remember to set the switch.

Mike

> Would it be ok to use a marine switch to separate two batteries that
> would switch everything on your van over to a different battery when
needed?
>
> Or would it be bad to actually run the vanagon with everything connected
> to the aux battery?
>
> I just figured that while camping, you could use the starter battery to
> get you going, but after a night of camping, switch over to the aux
> battery during the following day of driving, so you can fully charge it
> again before the next night of use?
>
> thanks for any tips!
>
> cr