0 gauge is way thick, 4 gauge works fine. The distance on my car is at least a foot more than would be required to relocate a battery anywhere in a 2.5rs. I have no problems cranking at -30c even with my crappy battery. Also used 4 gauge for a ground, FWIW I grounded to a seatbelt bolt on my audi, just make sure to sand away any paint on the surface you are using for a ground. Also, the box I used is not sealed, it was like 10$ from a marine store. However, the battery I am using has vent on it, and I ran a hose outside the trunk using the vent.