I design a quick 13S4P ebike battery. Total cost of battery is under $100.
Part 2 here
https://www.youtube.com/watch?v=b6sC0G6Lh0Y
Link to Battery Case
https://s.click.aliexpress.com/e/_DD1TBjb
Link to BMS
https://s.click.aliexpress.com/e/_DcxVC17
https://amzn.to/42wdg31
Places where i buy cells for salvaging
https://www.batteryclearinghouse.com/
https://jag35.com/