There may be a few reasons to do this;
- You can fit a bigger battery, the stock location on the S15 is limited, especially if you have done something silly like cut a hole through the tray (you dont need to do this to route intercooler piping)
- If you relocate to the boot, you improve the weight distribution by instead of having a 20~25kg weight over the front right fender, it can be in the centre of the car just behind the rear differential giving more down force to the rear wheels.
You can run the wires to the boot under the car or through the cabin. I didn't like the idea of having the wires under the car though you could probably find a more or less safe routing.
There is some debate as to whether one should ground the battery to the chassis within a foot or two of the battery itself. This has caused problems with starter motors not having a close enough ground. On the other hand, you don't want a large current grounding to all the way to the factory location with the extra cable. I am not 100% sure so I opted to keep the factory location to imitate the factory setup. This can be deleted easily enough later
The Cable Routing
10m 3 AWG gauge cable (5.83mm diameter) (between 2 and 4 AWG is generally accepted as thick enough)
I cut this to 5m for both pos and gnd and was a perfect length.
Crimp Terminal ends
~$8.95 for pack of 10
15mm diameter flex Plastic Corrugated Tube Electric Conduit
Other items you should also have in your garage if you are a self respectable enthusiast: Cable Ties, wire coat hanger to feed cable, electrical tape.
Run the cable through the flexi tube to prevent any abrasion. I saved money by buying a single length of 10m cable, cutting it and spray painting one length black.
Remove the front right wheel and trim under the wheel arch.
There is a port hole right next to the stock battery location where the windscreen washer reservoir is.
The cable can run through here and over the top of the wheel arch. Use cable ties to secure it out of the way.
The cable can enter the foot well by puncturing a hole through this grommet:
Remove the trim around the drivers side fuse box. There is one nut.
Once the cable enters the foot well it is routed behind the fuse box.
Now the cable runs along the under the carpet. The side skirting is clip in and can just be pulled off.
I routed the cable through a hole into the actual chassis siding skirt cavity to get around the hump where the boot/fuel cap lever is. The best way to do this is to feed coat hanger wire through taped to the cable.
There is another hole along the side skirting where the cable can exit.
Remove the rear seats and side trim on the right side.
Note where the cable exits the side skirting the carpet is a bit stretched to fit over the tubing.
Then the cable goes behind the bracket in the above photo
Note the cable could also exit through the above gap rather than the chassis rail as previously shown. It could also continue running through here to the boot - see blue arrow in the below picture.
The below photo shows the final routing into the boot.
Below shows the routing behind the trim, viewed from the boot.
I crimped the ends of the terminals with the help of a mallet and a block of wood.
The factory terminals were incredibly corroded. I took to them with a dremel with a wire brush bit.
After cleaning them up they can be bolted in.
The Battery Install
1mx3mmx50mm Aluminum bar from bunnings
M8 wing nuts x 2
M8 bolts 15mm x2
M8 bolts stainless 35mm x 4
Angle grinder. You should have this if youre not a fag.
I opted for this AC Delco with a beefy 900 CCA for $197. A lot of people go to battery shops or buy a brand name "performance" battery or try to squeeze an over priced slimline dry cell next to their intercooler piping. If you have auxiliary electronics you don't need to blow $400 on a brand name. AC Delco are also an official OEM part manufacturer so you know there is quality testing behind their products.
The 3mm aluminium bar required some cutting and shaping to fit the chassis bracket where it will bolt up. The 4 stock bolts are not long enough which is why you need tp replace them with the 35mm ones. They are M8 size/threading.
With the bar done now the battery tray can be bolted to it. This is what the short 15mm M8 bolts are for, though they dont have to be this size, use a wing nut so the tray can be removed if you need to access the spare tire.
Now put all the trim back, bolt up the terminals and youre done !
Looks pretty neat, though the bracketing could be made a bit more sturdier with angle brackets and what not if you wanted to.
If you like my article check out my build thread and guide on the S15 cluster
Edited by matth23, 14 January 2017 - 07:39 PM.