Shopping List:
Sealed battery with breather - $200 (required for ADR compliance and to avoid blowing yourself up with hydrogen gas from when charging)
Battery terminals -$10
Large battery box - $30 from Supercheap
Battery tray - $10 from Supercheap
Teks screws or M6 bolts- $10 from Bunnings
1m M8 Threaded Rod - $7.50 from Bunnings (for battery brace)
1m 1"x3mm Flatbar steel - $7.50 from Bunnings (for battery brace)
M8 nuts and washers - $2 from Bunnings (for battery brace)
6m red 0awg cable - $120 or $20/m from any auto electrical shop (try get the insulated and sheathed stuff - it's much tougher than that soft plastic clear sheathed only amplifier cable)
1m black 0awg cable - $20
3 0awg cable lugs w/ M10 centers - $15
Big battery block to take all wires - $35 from Autobarn
Restecp for not starting another "how do I relocate my battery to the boot?" thread - Priceless.
Install:
In my ED I mounted the battery box next to rear driver's side quarter panel (uses least amount of boot space there) and fastened it to the boot floor with 4 x teks screws. I then put the battery tray in the centre of battery box and fastened it down with another 4 screws. If you're feeling particularly enthused unlike myself you can always drill holes through the floor and bolt it on from underneath the car, but the 4 tek screws were enough to make it very sturdy.
For the battery brace I drilled 9mm holes above the top (front of car) and bottom (rear of car) ends of the battery tray through the battery box and boot floor. I cut the threaded rod into two pieces of suitable length for the height of battery, placed rod through holes and fasten in place with a nut, washer and loctite on both sides of the boot floor. When drilling the holes make sure you inspect from underneath the car where they go, otherwise they may end up in the chassis rail and you won't be able to get a nut on from underneath.
I cut the flat bar to suit distance between threaded rod and drilled holes at either end for the threaded rod to go through. Bolt the flat bar down over the battery on the threaded rod and it will not budge regardless of any awesome lateral Gs.
You will also need to drill a hole through the boot for the sealed battery breather tube. This will evacuate any hydrogen gas out of the boot made when charging the battery, thus avoiding a potential explosion.
Now for the wiring.
Run black 0awg cable from relocated negative battery terminal to one of the big bumper bar bolts or tow bar bolts if you have one (use 2 x cable lugs). Sand back the earthing point so it is nice shiny metal for the best connection. If you're paranoid about rust like me you can spray over it with a lick of paint once everything is bolted down. I drilled a hole through the side of the battery box at the very bottom for the cable to run through, under the boot carpet so it wasn't visible.
There are many ways to run and wire the positive cabling. I elected to run the red 0awg cable underneath the car directly to a distribution block where the battery used to be, and reconnected all the wires that used to connect to the positive terminal of the battery there. Another frequently used option is to run the positive cable from the relocated battery directly to the starter motor, then piggy back the existing starter motor cable from the starter positive terminal to the distribution block where the battery used to be, once again reconnecting all the wires that used to connected to the positive terminal of the battery there. Both work perfectly fine. In this tutorial I'll describe the first method that I selected.
Once you have worked out which way you would like to go, have a good think about where you want to run the cable and inspect the entire route before installing anything. I drilled a hole through the side of the battery box at the very bottom like the earth cable, ran under the boot carpet through to under the rear seat, then through the floor and under the car next to the chassis rail until around the B pillar, then into the chassis rails forwards from there to shield it from the heat off the exhaust, out of the chassis rails once inside the engine bay to its final destination.
Once you have terminated all positive wires that used to be connected to the positive battery terminal and (if you chose the same method I did) red 0wag cable onto the distribution block, connect all the negative wires that used to be connected to the battery to the existing earthing point on the chassis rails. Finally hook up your red 0wag cable to the relocated battery using the remaining cable lug. Turn on the ignition.
If everything lights up you're done. If it's on fire you probably should have taken it to an auto electrician.
