Entity jennifer dumpert spoke thus:

> Does anyone have advice/experience about this?
Yes. The good news is that a laptop doesn't use much power at all so you can
go for longer than you think without worrying about a dead Vanagon. A small
inverter will do nicely, say 100 watts, for the laptop and to power a
printer, cellphone, etc. You can run it for at least 12 hours before
compromising your cranking battery under normal circumstances.

Rather than go for the dual battery system you should consider an
alternative. I suggest a "Gel Cell" of manageable weight- say 20 or 30
ampHours, that will be manually connected to the Westy when driving for
charging. You may also consider a "plug in" charger for you driveway or
whenever you have a plug available. Batteries Plus,
http://www.batteriesplus.com has the best selection and stores all over.  I
suggest a 3-5 amp "Switched-Mode" charger because they are nonbuzzing and
lightweight and bulletproofed against low supply voltage.

Or you could just get a small UPS unit to plug into, but you couldn't charge
it while you're driving without special modifications. If you are prone to
regular excursions this may be the best solution because you can keep it
plugged into your driveway while you are at home. But if you're more of a
full timer like me that's not going to work out well.

You can see my setup here:
http://www.Gnarlodious.com/Vanagon/Electrical/System.html
Gnarlodious' Vanagon electrical system

Good luck!
--Gnarlie