I've been looking for a way to get some 4 awg power cable through the firewall on my 2017 JKU. I've seen a couple posts on a hole behind the battery, but no pics, and I didn't see one. I finally found it, so I thought I'd post some pictures. It is the same size as the drain holes in the floor, so the plugs will work.

It does force the wire down, and comes out behind the speaker in the dash, way up high in the corner. I removed the speaker, which was 3 bolts, then it came out through the glovebox hole. I couldn't even see the exit inside when I pushed the coat hanger through because of the other wires below it, but I could get them through by pushing from the inside while pulling the (well taped) coathanger from the engine bay. once i uncovered the hole by pulling back the insulation and tape, i had to cut and tear the felt insulation from inside the hole, then push through at a sharp downward angle.

The wire I used, since I had it, is marine grade 4AWG. The sheath is about 1" wide and 1/2" thick. I would say that 2 wires


0/1 AWG to 1 AWG would fit. I will be keeping an eye on the bottom of the wire where it bends over the bottom edge of the hole. Even though I have a rubber grommet there, I want to watch for cutting or wear on the wire from the edge of the firewall sheetmetal.