Interesting details from Dennis!

I installed GoWesty's relay system and their small aux battery when I
bought my '84 Westy in 2009.  Throughout the time I owned the van, I
noticed a big voltage drop from the alternator.  The current path from
the alternator all the way to the front of the van and then (through a
relatively small wire) back to the aux battery under the driver's seat
just isn't designed to provide a lot of current.  I always thought of
charging while driving as a stop-gap when shore power was unavailable.

At the same time, I installed a ProSport 12 charger.  I never tried to
deeply understand the charging cycles, but the ProSport is designed to
tend boat batteries, so I just trusted it to do the right thing.  It
always worked well.

(I was always tempted to install a smart DC-to-DC system for charging
smarter while driving, but as Dennis says, the charge cycle doesn't
complete between fuel stops, so it wouldn't be ideal for battery
maintenance.  Do those smart chargers "remember where they were" when
the engine is turned off at fuel stops?  Probably not.)

The sides of the small battery were bulging only two years after it was
installed, so I knew it was time to get it out of there.  I installed a
larger Interstate deep-cycle battery under the sink:

https://sbw.org/westybattery/

That battery went to Burning Man and lasted seven years.  Not bad!  I
replaced it with the same model.

I lived in the camper for years at a time, mostly with shore power at
campsites and friends' homes.  I was a heavier user than Richard: I had
a Engel fridge, propane furnace (rarely used), a 14-inch fan, computers,
and even a big computer display:

https://sbw.org/westydisplay/

Even without shore power, after a day of driving, boondocking overnight
under full load didn't deplete the house battery much.  I rarely went
more than one night without driving or shore power.

When I lived in apartments, I left the charger plugged in when I wasn't
driving.  That seemed to work well.

The Promariner charger failed after eleven years.  I replaced it with
the same model.

As for the starter battery, I don't know how old it was when I got the
van.  I replaced it five years later, in 2014.  (I didn't retire it, but
rather moved it to my diesel Rabbit, which I sold a year later.)  It
still cranked strongly when I sold the van in 2021, but I advised the
new owner to plan to replace it soon.

More details on my Westy, now with a new family here in Southern California:

https://sbw.org/sbwsty/