Moving battery to the trunk

[randy73]

How do you mount the battery tray and where do you run the cables?

[JR]

You can mount the box and run the cables however you like, really.

Some people prefer to run the cables underneath the car for convenience, some prefer to keep them inside. I prefer to run them inside the car, to keep them away from harm and the elements. You'd run them through the trunk, over the rear bulkhead, along the sill plates on the floor, and out the firewall to the starter. (I would strongly recommend you running them inside the car, personally.)

For the battery mount, you can simply bolt the original tray to the floor, or buy a sealed battery box. If you want the car to pass tech at a dragstrip, you need either a sealed battery box with a vent tube pointing through the floor, or an aluminum sheet separating the passenger compartment from the trunk. You can mount the battery on either side of the trunk. The driver's side is easier, but the passenger side makes for better weight distribution, and is really the correct location (from a performance perspective) (Be sure to use nuts and bolts with thick, wide washers. This way if you're ever in an accident, the battery won't tear loose from the floor.)

I'd also recommend using a Ford starter solenoid, so the main power line is only hot during starting. This is also a perfect time to add a quick cut off switch. I mounted one in the trunk as an extra security measure.

Some naysayers will state that relocating the battery to the trunk is a potential source of electrical issues. And that is complete b.s. There is nothing inherently less reliable about putting the battery in the trunk. Unless of course, you do sloppy wiring, make poor quality crimps, etc. I've had mine in the trunk for almost two years with no issue whatsoever.
 
 I would, however, stress the importance of good grounds if you do this. Wherever you bolt the ground cable too, be sure to grind down to clean, bare metal before bolting it. Plus, be sure to run a thick ground strap from the block to the chassis. So many electrical issues can be traced to bad grounds, and relocating the battery to the trunk can potentially show any trouble spots in your existing wiring.

There are also some helpful YouTube videos showing how to do this.

Here's a photo of my setup in my trunk. The alternator feed wires are ran thru the cut off switch, so flipping the switch will shut down the entire vehicle. There is a Ford starter solenoid hidden above the rear wheelwell.

The random small gauge wire in front powers some unrelated trunk lighting.

[alfaitalia]

All good advice. Did something very similar on a previous car. The only think I would say is use the thickest gauge wire you can that's still flexible enough to route where you want it to go. Power losses due to resistance will be rather more over that distance then when only a few inches away from the battery. This will flow more power at start up and the wires will stay cool. I too would NOT route the wires externally.

[Ghoste]

I mounted one in a 69 Charger years ago and I put the box on the passenger side and closer to the taillight panel.  I ran a heavy gauge welding cable along the same path as the taillight harness.

[c00nhunterjoe]

I used welding wire as well, ran inside, over the axle hump, along the passenger side, inside the sail panel, under the door sill, and thriugh the firewall. Never had a problem with cranking and the weight off the nose is noticable.

[timmycharger]

I wired mine pretty much the same way, no issues here either. Since I race my car at the strip, I have a shut off switch which I painted the color of the tail panel to blend in when on the street, and a red one for when I race.