My personal method was to use an isolation relay.  there are two
opinion  areas with the relay.  one is the method i chose which is the
heavy RV battery isolation relay available for about 14 bucks at the
local rv store.  the other method is the relay kit available from  many
of the online vendors made by hella. my reason for going with the
heavier relay was that i am using my setup in a bit heavier than normal
uses  and am a  chronic  overbuilder.   Isolation relay is also the
method  that VW chose.   it is  also  the method in most smaller  RV.
battery isolators are the next option.  these are okay if you have the
alternator to support it without having to mod the alternator.  most
bosch or motorolla  alternators made for VW need  to be modified.  i
have seen these used in many situations and they seem to function quite
well.
next is the batteries.
starting batteries - great for starting, lousy as aux
deep  cycle - great for  aux, lousy for starting
this is not  because they wont work in switched positions, just  not
for very long usually.
deep  cycle designed to be drained and recharged may times but not to
take  the heavy current hit of a starter very often
starting battery designed for the heavy hit of a starter but not the
recharging cycles of too many heavy discharges.
there are some batteries called  marine starting.  these are a blending
of both.
jimt
82westy
On Friday, Sep 27, 2002, at 08:45 America/Denver, Thomas Keefer wrote:
> Hey All..
> The posting about dual batteries has re-ignited my interest to hook a
> second
> up in my 7pass 88. What is the easiest/cleanest way to be able to run
> all
> the accesories off of the main battery. Is it easiest to just remove
> the
> regular battery and replace it with a deep cycle and then put the
> regular
> battery as your aux  then isolate the regular battery when in camp??