I packed both of my big li-ion batteries in the checked bag. The carry-on was the rest of the big rig, mics in the wooden boxes, apogee mini-me, cables, Microtrack, etc. When the bag was scanned at JFK, the security guy was not even looking at the screen, he was talking to someone on his left.
In Iceland, the guy said "electronic equipment?" and I said "yes" and he said "ok". That was it.