Ok so I've been wanting to do this for some time now. And I fianlly got the whole day to myself so I said hey lets do it. Here's my supplys: Battery box from walmart($7 ftw!) 4ga wire I had laying around 6 ring terminals(I lost one of them in my front suspension somewhere, still can't find it haha) That's pretty much it. Onto the pics. Sorry for cell phone pics! Here's my supplys. What I started with.I know, ugly. Battery out. grounds done. Under the hood finished. Amp wiring thru a gromet in cuby hole thing. And the batter in the box with all the wires ran(getting a new ring crimp to do ground to frame tomorow. And for laughs. Cuby hole cover. G'd out If you have questions or need more detailed pics lemme know.
Notice I put the fuse off the fender too. Well that's all done because their gettin cut out. OMG!! Yes im cutting my fenders. And yah jim my trucks got some bump!
4 Gauge is pretty small, you'd probably get better juice flow with a 2 Gauge positive. BMWs have a factory "relocated" battery. It's offset in the passenger side rear to help crossweight.
^^ yah Im actually gonna run another run of 4ga probably today. I would have yesterday but I lost that ring terminal. I just used 4ga cause I had a bunch layin around