I use a similar set-up....but I swap my older starter battery over to
use as the House battery, usually on about a 2 year schedule....I've been
getting about 2 yrs of life from my NAPA small batts, but I'm using mine
hard for at least two months of full time vanagon per year...

   I have one of those can-nstyle solenoids that 'clunk'...it's hooked to
the circuit that is only powered after the van is running...   I also
installed a switch just under the driver's seat to send power to that
solenoid so I can manually connect or disconnect the aux battery circuit
from the starter battery..When I run my coach battery flat and my starter
battery is down, I leave the coach battery out of the system till I run for
a while, then I hit my secondary switch to equalize the two batteries while
the engine is on.   Most of the time I just let the cannister solenoid do
it's thing....

On Wed, May 6, 2015 at 8:16 PM, Richard Koerner <rjkinpb@sbcglobal.net>
wrote:

> Went out a few days ago to start my 85 tintop Vanagon; ugh...  No start,
> no click, no nuthin, but lots of red lights on dash.  Radio played;
> headlights turned on.  I have GoWesty auxiliary relay for house battery (a
> Walmart group 41 purchased about 6 years ago)...and it strained also..the
> reassuring "click" of switching to main battery was slow in coming.  And, I
> listened to my fuel pump; normally 2 strong pulses of fuel pump before
> engine ignites.  Not this time.  Instead, it groaned.
>
> Got out voltmeter.  Only 11.37 VDC (Harbor Freight freebie voltmeter)
> across terminals.  Internet research says battery is dead.
> Got out my records....well....it's been 12 years on my Kragen (now
> O'Reilleys) group 41 battery.  Yeah...I've been meaning to change it!  You
> know how it goes.
> Went to Walmart for a group 41.  New price is about $100, old price 12
> years ago was about $60.
> Anyway, put it in.  Started right up, all systems GO.
> I drive about 5,000 miles a year in my beloved Vanagon (second vehicle);
> it's in my garage in San Diego, so pretty mild weather conditions.  Still,
> I'm thinking 12 years is amazing.
>
> BTW....no corrosion noticed on terminals.  Good climate here.
>
> Just FYI for you guys...I know you replace your starter battery before you
> are stranded, right?  (Oh, I guess if I was stranded I could have jumper
> cabled house battery to starter battery).  But, after 12 years, I figured
> the starter battery had given more than anybody could expect; very pleased.
>
> RichSan Diego
>