I’ve been seeking a 48V (14S) Li-Ion pack for testing purposes. Current requirements are light.
Inspired by Jehu Garcia / Justin Kenny, I decided to simply construct a pack from 18650 battery holders. Originally, my intent was to make a single 14S board, but in the end two 7S boards in series made more sense from a PCB fabrication standpoint. A single 7S board can be used for 24V, if required.
You can obtain gerbers for Jehu Garcia / Justin Kenny board at https://kit.com/jehu/jehu-s-diy-powerwall-pcb-project however I decided to make some minor tweaks for my purposes (Anderson connectors). My intention is not to make parallel packs.
Justin has done some great work by costing down with PCB trace fuses, if your intent is to mass produce these modules.