A little background: in order to fit the IC core for the water-air IC setup I'm planning, I decided to relocate the battery to the trunk. After a little bit of planning and putzing around, I finished the project up last night. Here's a material list and a basic walkthrough... Parts/Materials -Sealed battery (i.e. Optima) -25' of 0 gauge welding cable (I got mine here) -Group 24 marine battery box (about $12 at an auto parts store; if you don't have a sealed battery, you will need a box that is sealed to the interior of the car, and vented out of the car somehow) -150 amp circuit breaker (I used this one) -Distribution block, preferably with both fused and unfused outputs (This is what I used) -0 gauge ring terminals with both 5/16" and 3/8" holes. -Battery terminals with ring terminal connections (Like this) -zip-ties -electrical solder Tools Needed -Various metric sockets (specifically 10,11,12,14,17mm) -Drill/bits -Propane torch -Large linesman pliars (or something specifically for cutting heavy cable) -Bench-mounted vice -Utility knife First thing I did was pull up the carpet in the trunk look for a suitable pass-through for the main battery cable. I decided after nosing around the car for 30 minutes or so, that routing the cable under the car would be less hassle than going under the carpet and drilling a hole in the firewall. Right at the back of the spare tire area, there's a giant rubber grommet--perfect! I drilled a 1/2" hole through that, then pulled about 4 feet of the 0 gauge up through from the bottom; enough to locate the battery anywhere in the trunk. From the top, and from the bottom I decided to run the cable up along the drivers' side of the car. I went up over the rear crossmember, above the lip of the gas tank, and then along the brake lines, securing with zip-ties as often as necessary to ensure the cable doesn't sag. There are probably better ways to secure the cable, but didn't feel like drilling holes into the floorpan if I didn't have to. Pics, going from the rear of the car to the front Finally, I pulled the cable up along the firewall, making sure it was going to be clear of the axles and suspension. Sorry, no good pics except for where the cable ended up in the engine bay Now that the power cable was in place, I decided to locate the ground wire. If you pull away the trim in the trunk, the bracket that holds the seats to the frame offers a nice heavy secure bolt to ground to. I used a wire brush to clean up the metal around the bolt and on the bracket itself. A ring terminal with a 3/8" hole was perfect. I guess this would be a good place to point out why I listed solder and a propane torch in the tools/materials. Main reason is that securely crimping those large terminals is a PITA without the proper tool (which I don't have). An alternate method I read about requires that the wire attachment point be closed at the end, like this as opposed to open like this. Once you've stripped the end of the wire, you put the ring terminal in a vise with the wire opening pointing straight up, and fill the wire opening with bits of solder (like literally fill it). Then you torch the terminal until all the solder melts and jam the end of the wire in there. If done properly, it makes a damn good mechanical and electrical connection. Anyways, back to the walkthrough.... I then went back to the engine bay, removed the strut bar, unhooked the battery, removed it, and removed the battery tray The distribution block I bought has three fused outputs and one unfused output. Given that the stock battery connection has a cable running to the fuse box, and a larger cable that I assume runs back to the starter/alternator, I ultimately decided it was fine (and simpler) to hook both of those to the unfused output. For lack of a good idea on where to permanently mount the distro block, I just zip-tied it to the fusebox lid. Now back to the trunk to mount the circuit breaker and locate the battery box. I decided mounting the circuit breaker to the battery box was as good of an idea as any. I just drilled a couple 3/8" holes and used some spare machine screws to mount it. The circuit breaker has 5/16" studs, so that's where the ring terminals with smaller holes come in handy. The main power cable gets attached to one of the terminals on the breaker, and then I cut a short piece of cable to run from the battery terminal to the breaker. Note the battery terminals I linked to use a 3/8" ring terminal All I had left now was to mount the battery box. The one I bought just uses a couple of brackets that screw into the frame, and then a strap that holds the box to the brackets. Not an ideal solution, but it holds everything down tightly. I was deciding between two locations. Behind the passenger sidewheelwell, or up against the rear passenger side seat. Against the passenger seat probably gives a better weight distribution, but it would completely block off any storage with the seat folded down. So I put it in the nook behind the wheel well. As a final test, I hooked up the negative terminal and turned the key. She fired right up! I was a little concerned that a 150 amp breaker wouldn't handle the current from the starter, but I saw a walkthrough on a subie, where only a 100 amp breaker was used, so I should be okay. The real test will be on a cold morning in the winter when the starter sees it's maximum load. Here's my filthy dirty engine bay, sans battery! Oh, and a box the approximate size and location of the l-a IC core I'll be ordering soon I've got a couple things I want to clean up, but they are lower priority now that everything is functional. Main thing is that I want to replace the main power and ground cables in the engine bay with something a bit beefier. I also think I want to eventually replace the battery box with something that uses a standard tie-down.