SYS_MODULE // 02
E-Bike Conversion
PWR_SYS 18650_CELLS SPOT_WELDING
> Exec_Summary
As a 15-year-old working at a bike store, I was inspired by YouTube personalities like GreatScott! to build an e-bike from scratch. Instead of buying a premade pack, I sought to build a battery system that would be cheaper and use higher quality cells.
> V1_Architecture
I utilized a 1000W hub-driven motor conversion kit for a 26-inch Trek bike. The battery pack was composed of 26 Samsung 25R 18650 Cells in a 13s2p configuration, yielding a nominal voltage of 48.1 volts and a 5 amp-hour capacity. Under full load of 20 amps, the 1000W motor could theoretically operate for ~15 minutes.
The initial build relied on slot-together plastic pieces with prefabricated nickel strips held by small hex nuts. Everything was press-fit without springs, creating a major safety concern regarding intermittent contact and dangerous voltage differentials across parallel cells.
> V2_Revisions
The V2 iteration moves the system to a 29-inch Cannondale hardtail with more frame space. To resolve the electrical connection issues from V1, the design requires using a spot welder to fuse nickel tape directly to the battery terminals. After waiting for portable spot welders to become accessible, I acquired one and am preparing to finalize the V2 build.