I do agree it might be cheaper but what if you short out the series of cells and have to replace them? Then the big "your time making the pack" and additional materials for a box. I have 32pcs 38120 lifepo4 cells in my pack and they're almost $20 per cell. and I only paid $530 plus the whopping $200 for hazmat shipping.
With my luck...Call me chicken but I'd rather pay more now then a lot more later.
I've seen an ebike pack catch fire at the races and that was enough for me to say: "I wasn't going to be one of the guys that went up in flames"
The packs at the race track are often rc lipo batteries and it is not that hard to get them to burn.
Sometimes it is part of the show ?
I would suggest that if you are afraid of your batteries burning to use lifepo4.
Most all lifepo4 is not so easy to get to burn.
I have taken 100s of battery packs apart and found a lot of times just one or 2 cells bad.
The whole pack got thrown away because just one or 2 cells failed.
They are throw away packs, not meant to be repaired.
People do repair them sometimes but changing out soldered or welded together cells can be a pain.
Batteries like the Headway packs are meant to be repaired and are easy to build and change out the cells when one goes bad.
We weld and make frames and build motors here, this is Motorbicycling.com.
Buildiing battery packs is something motorbicyclists do too ?
Not as hard as building a strong wheel or rebuilding a motor ?
http://headway-headquarters.com/diy-battery-kits/