> How much do I have to modify the compartment behind the driver's seat to
>accomodate the battery?  Also, do you have to "tie" the battery down?  I was
>hoping to be able to put the battery in a plastic marine battery case.  Has
>anyone found a decent battery that would fit in a plastic case and still fit
>in this compartment?  I do have swivel seats.  How much should I expect the
>dealer to charge me to set up this system?  Finally, if I just put the batter
>in and the terminals touch the metal top of the compartment will I have a
>problem?

no mods just buy the right size<g>

yes, bolt it down

forget the case, put a piece of cardboard/carpet under the battery for 
slight insulation value, in a sealed tray if you find one, rustspraying the 
compartment pays.

as much as they want

yes, but it will be over before you've even begun to pucker up, likely a 
loud arcing noise, followed by the vehicle stopping dead, followed by smell 
of ozone and burned paint, and possibly a ruptured or exploded battery due 
to the internal heat generated when fully shorted over

Think this over carefully, maybe talk to an RV dealer instead of high $$ VW.

         My Westy is wired with a second battery that fits under the drivers 
seat with a 1/8" hardboard cover under the metal flip lid.  The battery has 
a thick 1 gauge ground strap onto the body and its bolt + bracket holds down 
the battery too. A 10 gauge red wire (under the carpet), inline 10amp fuse 
and a 20 amp switch lead to the normal battery positive terminal.
        In normal use flipping the switch ON will let the second battery 
charge, and both batteries power the fridge/lights/pump. Flipping it OFF 
makes sure only the 2nd battery powers the kitchen stuff.  If I leave the 
switch on and start the car I may or may not blow the inline fuse. I didn't 
want to use awkward heavy gauge wiring so the fuse is to protect against too 
much current draw.  This is a poormans battery isolator.  Manually operated. 
 When you park, turn the switch off, camp away, (otherwise you may drain 
both batteries). When you are driving turn the switch on to top up the 
battery. If you blow the fuse the indicator lights on the front panel will 
not ever glow green, just yellow, when running.  For cold weather starting 
boosts an single cable will join both batteries for real current flow.
        Oh, even better would be to use a VW relay wired into the system 
properly instead of the switch, sorta like the factory install <g>.   Tim Smith