So this is my first honda (used to Dodges). I was suprised by this fuse box on top the terminal. It has 3 bolts on the box itself and a larger maybe 12mm? 13mm bolt next to the post. What do I need to remove to swap the battery? I don't want to disassemble the fuse box if I don't need to. I've already taken off the battery terminal bolts.

 

You don't disassemble anything in the fuse assembly you're mentioning. That whole fuse assembly is connected to the terminal bolt

So - you just undo the terminal bolt and lift the whole assembly off as one unit. See picture.

 

My 2012 had a bar clamp on top of it but it was just two nuts on a post screw

 

From what I've seen, it seems like only the 2013s are blessed with this weird battery fuse assembly on the positive terminal bolt

 

Yeah my 2013 has it too but after a 1 yrs with stock battery I switched the D51R Yellow top Optima battery and haven't regretted it since, I also use my Optima Digital 1200 charger for Maintaining it when not driving so I haven't had problem with it so far.

 

I did the battery upgrade to a larger battery 51R, replacing the riding lawn mower sized Fit battery. It was like 2 years ago on the 2012 fit.
I do remember getting the angle grinder with a cutoff wheel out to make some change. I figure the car works for be, not the other way around.
Much easier to find a 51R battery when in need next time.