Purpose

In order for any car to handle well on the road, the weight distribution across the axles should be as close to 50% / 50% as possible.  Because the Fox's engine is longitudinally-mounted, there is a bit more weight over the front wheels and in front of them when compared to a car with a transversely-mounted engine.  You can help move some of the weight to the rear of the car by relocating the battery to the trunk.  The basic idea is to move the battery into a special box in the trunk (so the acid won't leak if there's a problem), and run the wiring to the front of the car by means of the interior.

• Marine-grade battery box (make sure to get one that your battery will fit in. I.e. take a tape measure)
• Sheet metal screws to mount box securely to floor of trunk (approx. 5)
• 15-20 ft of 4 GA or larger audio grade power cable (it's more flexible if it's audio grade, easy to get where you want it)
• battery terminals (2)
• 2 ft. of 4 GA or larger audio grade ground cable
• 1 large bolt
• 1 small washer for large bolt
• 2 washers for large bolt
• 1 nut for large bolt (preferably self locking)
• O-ring connectors for other ends of cables

I read this a while back on the VW Watercooled newsgroup.  It was in reference to moving a battery in a GTI, but the source for the wiring is a good one - from a used Audi.

Instead of spending 40 or 50 bucks on 4 gauge wire from a hardware store (the stuff that doesn't bend), you can either go to a welding store and find it cheaper or go the easier route and not reinvent the wheel, so to speak.

Audi 5000's have the battery under the rear pass. seat and so, if you do the figuring, they also have a pre-cut, preinsulated cable of around the same length (a bit long) with ends on it to use for the same purpose.  In junkyards, I saw at least 5 or six of these cars and the cables were always there.  Today, I paid 2 bucks for mine and just followed it under the carpet and yanked the sucker out.  Took 10 minutes including figuring out how to get to everything.  The cable does have a union in the middle where it jumps a size and type of insulation, but that shouldn't pose a problem.

Hope this helps and saves guys like me the cash they work hard for.

Make sure to run a ground strap from the motor to the body.  I used a strap from one of the old mounting holes for the a/c bracket (took that off a while back) and ran it to the front motor mount bolt on the body.  The car won't do anything if you don't run a ground;  all the motor mounts are rubber, so the motor is insulated for the chassis, unless you do this (nothing grounded to the motor will work without running a new ground first).

Don't run the new wiring UNDER the car.  Go through the interior.  You can run them under the carpets, just make sure they won't rub up against anything sharp and cause problems.  Also secure them around the front seat rails, so they can't move in the way and be cut.  There are a few unused rubber plugs in the firewall which you can use to get the wiring to the engine bay.

Use at least 4 gauge wire or thicker.  (The lower the number gauge, thicker the wire;  so 2 is thicker than 4, for example).  Anything less than 4 gauge would be dangerous, and you'd have problems with starting and charging.

When making a ground from the battery, make sure you have a LARGE contact area (metal touching metal) where the strap meets the body, or you'll have the same problems as above with the wire gauge thing.  I used a ¼" thick bolt, and two 1" wide washers, stripped everything where the washers would
touch the body.  Make ground strap (wire) as short as possible.  Paint can cause problems, so scrape off any on the contact area(s).

Be sure to leave clearance around the box, so you can access the rear taillights.

The pipes running through the rear right side of the trunk are for the fuel filler.  DON'T ground to them!!

The total cost is about $60-$70, depending on the gauge wire you use.

When you run the wire from the starter, make sure it's not close to the exhaust! That's not heat resistant wire (usually).

Remove battery.

Remove all wiring (grounds) and coil from battery tray.

You can remove the battery tray to save a little bit more weight at the front end.
(NOTE: fuel lines run directly UNDER the battery tray, DO NOT CUT THROUGH THOSE!!!!!)

Mount the voltage coil and wiring (grounds that were grounded to battery tray), wherever you would like along the firewall.  It's easier to do it up as far as you can, so you can mount a bolt/nut combo through the firewall where the drip tray is (you have to remove the drip tray cover thingy to get into there, but it mounts more secure than just screwing into the sheetmetal)

Run power cable through interior of car as you see fit.  Run it through the firewall, about where battery used to be, the run the trunk end of the wire through the cabin to the rear passenger side corner of trunk.

Connect the engine side of power cable to the starter and other wires that were connected to the + terminal on the battery (accomplish as you feel fit;  I wired it to the starter first, then up to the other wires).
NOTE: run the wires as far away from the exhaust as possible, I routed them around between the fender and airbox and used several zip-ties to keep it in place.

In the trunk, mount the box. I mounted it transversely (parallel to the rear of the car). It needs to be on the rear most passenger side corner.  Keep in mind that you need to leave enough space between the box and the taillight assembly so you can change your bulbs (measure the room with the lid OFF the box, so you can get it back as far as possible).  Once you have it in place where you want it, check the lid to it to make sure you can get it on and off easy from where the box will be mounted.

Place the strap for lid under the box, then drill one pilot hole in the center of the box (SMALL pilot hole) through the trunk floor. (Don't worry, the gas tank is farther up over the axle...hehehe)  Screw the box to floor with sheet metal screw.

Install other 4 screws as you like.

Put the battery in the box, with + terminal towards side of car, and - towards the inside of the trunk.

Drill a hole for a large bolt through floor of trunk, as close as possible where the - terminal on the battery is.  Best to drill a small pilot hole first, crawl under car to make sure you didn't drill too far towards back of car, cause if you did, you can't get to the underside of the bolt to screw on the nut.

Using a sanding or grinding bit on your dremel (whichever you want, or you can use a knife or something, sandpaper, whatever, but this is easier).  Remove all paint, undercoating (under car), to expose bare metal where the washer will be touching the car around the bolt.

Put a small washer on the bolt, O-ring fitting for cable (with cable clamped into it already), and large washer on bolt.  Put the bolt through the hole. Put the washer then the nut on the other side and bolt down as much as possible.

Now, install the terminal on the + cable (cut to length if you like, but it's not as important as it is for the - one, although you don't want three feet of excess!).  Put the battery in the box, and figure out how much slack you need in the - cable to connect the terminal to it. Cut off all available excess. Install terminal.

Back up front, you need to mount a ground strap from the body of the car to the engine, if not already equipped (not usually). I used a ground strap that goes from the tranny/engine mounting point on a cabriolet to the battery I had. Mounted it from the old A/C mounting bracket holes to the front engine mount bolt.  Just make sure it's grounded well.  Since the engine mounts are rubber, without a direct line from the battery going to the engine anymore, nothing on the engine is grounded, i.e. won't work!

Check all wiring to be sure you didn't ground out anything.  Re-connect battery, and enjoy!

Big thanks to Josh, a fellow VW enthusiast for this information!!

If you have any questions, you can e-mail me, but because I haven't performed the upgrade myself, I cannot relate anything from experience; you can also contact Josh with questions about this.