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Old 03-06-2007, 04:58 PM   #1
Scooby Newbie
Member#: 115828
Join Date: May 2006
Chapter/Region: SCIC
Location: Bakersfield
2004 Impreza WRX STI
Platinum Silver

Default Down and Dirty Battery trunk relocation

This is not a job for those faint at heart. It involves working with the electrical system and taking a number of areas of the car a part. This is an overview of what was done. It is not a step by step process nor a parts list.

Please observe safe working

Keep in mind that your trunk will not be pretty anymore since a lot of the carpeting that covers the wheel wells and floor will have to either be modified or discarded.

An important note: There are a number of ways this can be done. You want to make sure that safety is a huge factor. I've seen setups that used ford starter solenoids or ones that reccomend double wraping the cables to protect against chaffing.

This is where the 175 amp fuses come into play. I used one on each end of the positive cable under the hood and in the trunk. The fuses are rated up to 300 amp intermittent use. and run around 5.00 each at the local parts store. That is more than enough to start the subie!

I relocated the battery to the trunk for a few reasons.
1). Better weight distribrution.
2). Opens up an area under the hood
3). Has an old school flavor to it.

Summit battery relocation kit w/2 gauge wire
Battery cut - out switch
4 - 6 copper lugs crimp style
Assorted bolts
2 - 175 amp fuses (optional)
Smaller battery box (optional)
Quick disconnect cable/post clamps (for battery side)
Shink tubiing various sizes
12L intercooler tank
sprayer Autoswitch

Air Chisel (used to remove brackets in trunk (STI water tank)
Asst. drill bits
Air rachet
Asst. Sockets
Asst. End wrenches
Asst. Screw drivers
Sledge hammer

Disconnect the battery and remove

Plan out where in the trunk you will locate the battery. Research I performed stated that the battery should be placed as low as possible in the trunk. There was noway that my daily driver would hold a battery where my spare resides. Other articles said that behind the passenger side rear tire. This meant that the intercooler water tank had to go.

That was fine since I really wanted the STI spec C tank which was larger and included a auto sprayer switch.

I removed the tank then chisled the brackets at the spot welds. You will need to be careful not to tear the metal.

Next was laying out how the box and j-hooks would be setup. Before you drill holes you will need to unbolt the evaporative canister under the car behind the rear wheel on the passenger side. Otherwise you could easily punch holes in it.

Next is deciding where in the trunk you will place the ground. There are some good spots and since I only like to drill as few holes as necessary there are some that can be re-used. I used an empty hole next to the antennea amplifier.

Once your box is setup and you have planned where everything will be located now comes the time to take apart some of the upholstery and remove the intercooler. This the part I was not looking forward too since I have removed the intercooler before and it is a real pain in the ass. Especially if you have a strut bar.

For safety sake I ran the positive cable inside the car this meant that the insterior would have to come apart to some extent and that the intercooler would need to be removed. At least in my case. The ideal location and grommet is located under and behind the intercooler under the hood. If you have a factory boost gauge this is where they ran the vaccum line.

I'm guessing it is the same as a WRX. You will need to remove the driver side kick/scuff panels
front and rear and the b pillar cover. Then remove the seat cushion (bottom) from the rear seat. Now you will be able to run the positive cable. I ran mine from the trunk to the front. When you pull the carpeting back you will notice a tray and some clips that look like they were meant to hold the cable. I used these to limit movement of the cable and hopefully help eliminate chaffing. I also zip tied the cable to the chassis stiffener (under rear seat).

Feed the cable through the firewall to the engine compartment. Once under the hood you will notice that the old negative battery cable is bolted to the transmission and has an accessory cable attached that gets bolted to the body. Obviously, this is no longer needed. At least not in this configuration.

You will need a good ground. Remove the old negative cable and cut off the terminal post end and replace with a copper crimp lug and reattach to the transmission on one end and the body on the other. I bolted it to one of the strut studs. You will have two positive leads now. One goes to the starter and the other goes to the alternator. These will be attached to the positive cable that was run from the battery in the trunk.

Optional: Between the new battery cable from the trunk and the existing cables under the hood (alternator and starter) I bolted the 175 amp fuse. Under the hood is completed up to this point.

Go back to the trunk and make a ground that attaches to the negative side of the battery and the body. Then make a short positive cable that will connect to the battery and the cut - off switch on one of the terminals of the cutoff switch. On the other side of the cut-off switch (optional) bolt the other 175 amp fuse. Then put a copper lug crimp on the positive cable (that runs to the front of the car) and bolt to the other side of the fuse.

The cut-off switch will cut power only if the car is not running. If you want the cut - off switch to completely kill the power then you will need to run the alternator cable to the trunk and connect to one side of the switch then back to the front.

Replace the intercooler.

Reassemble the interior

Turn on the switch.
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