S15 Battery Relocation Guide

[matth23 2]

This is a guide based on the way I relocated my battery to the boot. It was actually easier than I expected; I didn't have to remove any panels, only mostly clipped in trim.

 

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.

 

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

 

Part 1:

 

The Cable Routing

 

Parts required:

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.

~$80

 

Crimp Terminal ends

~$8.95 for pack of 10

 

15mm diameter flex Plastic Corrugated Tube Electric Conduit

~$10

 

Total: $103.95

 

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.

 

This is the general idea of the routing:

 

 

 

Generic terminals to suit 0-3 B&S gauge cable.

 

 

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.

 

 

 

Use heat shrink with electrical tape to insulate the connection. If you dont ever want to go back to the stock location then deleting the factory terminals and installing a terminal block will be the way to go. Either way ensuring proper insulation is essential.

 

 

Part 2:

 

The Battery Install

 

I put the battery in the centre with no box. I didn't really want to second guess what I may or may not get defected for. My battery does have a vent hole which I will route to atmosphere.

 

Parts:

 

1mx3mmx50mm Aluminum bar from bunnings

~$15

 

M8 wing nuts x 2

~$3.65

 

M8 bolts 15mm x2

~$4

 

M8 bolts stainless 35mm x 4

~$11.96

 

Battery Tray

~$35

 

Angle grinder

 

I opted for this AC Delco with a beefy 900 CCA for $197. 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.

 

My battery has a ventilation hole. I used some rubber tubing to route the gasses to outside.

 

If you like my article check out my build thread and guide on the S15 cluster

Edited June 17, 2017 by matth23

[pmod 261]

Nice work. As a suggestion to improve your setup, replace the bolt and nut on the factory terminals, then clamp the bolt down using a nut to turn the bolt into a stud. You can then shim the seating surface for the ring terminal using washers [to clear whatever is around], and bolt an un-shaved ring terminal in place. The less copper that's removed from the terminal, the less likely it is to distort and tear when the cable is moved.

 

You can then cover the entire oem battery terminal with a couple of layers of 50mm heatshrink tubing (double-wall with glue), pressing the overhang either side whilst hot for a watertight seal. Tuck the oem terminals to the side and zip-tie them in place, or cut some slots into two tiny plstic jiffy boxes from Jaycar, and bolt the boxes in place, so as to remove absolutely any chance of a short. With the jiffy boxes you don't really have to heatshrink the cable.

[The Big Fist 19]

Great writeup !

[1.5J 180 0]

Thanks for the write-up, great work

[matth23 2]

Nice work. As a suggestion to improve your setup, replace the bolt and nut on the factory terminals, then clamp the bolt down using a nut to turn the bolt into a stud. You can then shim the seating surface for the ring terminal using washers [to clear whatever is around], and bolt an un-shaved ring terminal in place. The less copper that's removed from the terminal, the less likely it is to distort and tear when the cable is moved.

 

You can then cover the entire oem battery terminal with a couple of layers of 50mm heatshrink tubing (double-wall with glue), pressing the overhang either side whilst hot for a watertight seal. Tuck the oem terminals to the side and zip-tie them in place, or cut some slots into two tiny plstic jiffy boxes from Jaycar, and bolt the boxes in place, so as to remove absolutely any chance of a short. With the jiffy boxes you don't really have to heatshrink the cable.

 

Yeah, thats definetly a better way I re did the front terminals after i realised i didnt need to grind them. I will probably add a fuse near the battery too.

[Protius 43]

The best way to go about this is earthing to a good solid ground in the boot. Have done this on many customers cars without any issue. Or if you feel the need to run the negative all the way you should be bolt it to the block as your engine needs the best earth out of anything for the car, one for the starter and two for all the engine sensors etc. The other thing you should do is run the positive all the way to the starter motor directly so the starter has as short a run as possible. You then leave the factory starter motor power cable in place so power up the fusebox etc this way you don't have to do any dodgy joining or bolting etc. To better this again, remove the factory terminals all together and crimp on a lug that then bolts to a proper insulated power distribution post which will also double as an easy point to put jumper cables should a time come you can't access the battery in the boot.