The problem with just connecting the second battery in parallel is that
they both discharge at the same rate and at the same time.   A primary
reason for wanting a second battery is to avoid the embarrassment of
needing a jump start after using your 12v camping appliances too much (12v
blender for the fish, 12v dishwasher, etc.)
When the aux battery is hooked up either with a diode isolator, or with a
relay isolator, the two batteries can discharge (or not) independently but
are both charged from the alternator when it is making whizzies.    Late
model campers (at least) have a relay under the driver's seat that prevents
the fridge from running off 12v unless the alternator is making the
previously mentioned wizzies (a technical term), and so the easy way to
hook up an aux battery when the isolation relay is there, is simply to put
it in parallel with the fridge.   I actually connected mine through a 30A
fuse to avoid even more embarrassing fires.

Dave
87 Wolfsburg
90 Westfalia

At 08:34 AM 10/7/98 +0800, Steven Cu wrote:
>Philip,
>
>I added a 2nd battery to my 82 Westy, it was just connected in parallel(
>The two batteries are new), the ground wire is bolted to the body, the
>positive is just connected to the other battery. The hard part is routing
>the positive wire to the main battery, some people would use an isolator
>but I have been using this set up for 3 years and it has not given me any
>problems sofar
>
>Steven
>82 Westy
>
>----------
>> From: Philip Hanson (Volt Computer) <a-phanso@MICROSOFT.COM>
>> To: Vanagon@VANAGON.COM
>> Subject: Adding the second battery to the early vanagon ('80)
>> Date: Tuesday, October 06, 1998 2:34 PM
>>
>> I have an 80 Westy.  In the aux battery compartment is a heavy wire pack
>and
>> something that looks like a fuse holder.  I want to add the battery here.
>>
>> Can anyone suggest where to go in the archive for instructions.  One I
>found
>> only addressed the newer vanagons which seem to have a different setup
>than
>> mine.  Or, has someone done this job and can give me hints?  Thanks. ph
>