I need to make exactly like this, two 3V camera batteries connected and need the cable, then the battery pack is wrapped in tube. I can not use any battery case because this battery pack will go inside of another case. So it has to be wrapped in the plastic tube as you see in the photo.
The metal piece between the battery ends and cable doesn't look like it's soldered, but attached with some sort of stapled. Then the battery body is wrapped in some sort of tube which seems as it shrinks when heat is applied.