Excellent question, Loren. I was asking this myself yesterday after my van
had died and i was trying to restart it.

The van had sat for two weeks without being started. Prior to that, I had
run the battery down by leaving the radio on but had drive for about 1/2
hour after jumpstarting. Apparently, it was not enough to call it a helathy
charge.

---------- Forwarded message ----------
From: Loren Busch <starwagen@gmail.com>
Date: Sun, Mar 9, 2008 at 1:16 PM
Subject: How Long Running to Charge the Battery After Starting?
To: vanagon@gerry.vanagon.com

Here is a question for the Vanagon electrical gurus out there.  I've always
been of the understanding that the folk wisdom of "If the vehicle is going
to be unused for a period of time start the vehicle and let it idle for a
while to keep the battery charged" was a bad idea because it took more
energy from the battery to start the engine than you got back with a 'few
minutes of idle'.
So the question is, just how much engine running (at idle) or how much
running on the road does it take to replenish the energy used to start the
Vanagon?  BTW, this assumes easy starting, a healthy engine/FI/electrical
system.

--
mordo
1990 Carat