I started from scratch a few years ago, so for sure you can do the same. Its very difficult to start, but then its relatively easy. I can give you the first hour of training in Fusion360 to get you started, I owe one guy from Autodesk a favor :-)
Autodesk Fusion 360 is free if youre a student, startup etc.. Check it out.
The batteries are 18650 cells, we designed some custom batterypacks and welded them together with a special welder for batteries. Its not as thin as lipo packs can be but more safe in terms of fires etc.