Building my own e-bike meant learning everything from scratch — wiring harnesses, connectors, battery packs, controllers, component layout, BLDC motors, Hall sensors, diagnostics, BMS systems, 3D printing, etc.

I started with an e-bike frame, a 750W geared hub motor, and both a faulty battery pack and motor controller. I performed detailed diagnostics to determine each failure.

When testing the battery pack, I found the BMS was cutting off: the P+ and B- terminals showed full voltage, but the P- discharge terminal was dead, indicating a failed component on the board. Since they covered most of the board with clear epoxy, diagnosing the BMS on a component level was near impossible, it was best to just replace.

The controller was also faulty. It powered on with a 48V supply, but the motor wouldn't run. After verifying the motor worked with a different controller, and performing MOSFET and phase-wire tests, I confirmed the controller as the issue.

Below are photos of the battery pack and controller testing.

I determined the original battery and controller were beyond repair, so I moved forward with a full rebuild. Since I wanted more power, I converted from the stock 48V 14Ah pack to a 60V system. I disassembled the original 13s4p battery, salvaged its 52 cells, and capacity-tested each one.

To reach a higher voltage without exceeding my usable cell count, I chose a 16s3p layout — 60V nominal and roughly 10.5Ah, using 48 of the cells. I didn’t have a spot welder at the time, so I hand-soldered the pack using nickel plates, then wired in a new 16s BMS and sealed everything in heavy-duty PVC heat-shrink.

(Images below show the soldering process and the initial 13s3p layout. This was my first full battery build — a challenging but valuable learning experience.)

With the battery pack complete, I moved on to mounting the new controller. I designed and 3D-printed custom brackets that clamp securely to the 1.275" seat tube, providing a stable mount for both the controller and the rebuilt battery pack. This ensured a clean, compact installation tailored specifically to my seat tube. 

I created a full part-level wiring schematic for the system (see attached below).
It outlines all components required for a functional e-bike, including:

• Battery and BMS connections

• Throttle and ignition inputs

• Hall-effect sensor wiring

• Three-phase motor outputs

• Controller signal and power routing

This diagram served as the master reference while assembling and troubleshooting the entire electrical system.

To validate the wiring diagram, I built a bench-test setup using the rebuilt battery, the new 60V controller, and a spare scooter motor (video below). This let me confirm throttle input, hall sensor feedback, and three-phase motor output before installing everything on the bike.

In the video I mistakenly mention the motor making less than 1000W — that was before testing under load. Once loaded, the system drew ~25A at ~50V, producing roughly 1,200W. After confirming stable operation, I mounted the pack and controller to the frame and took the bike for a test ride. The result: strong torque, especially on climbs, and very sharp throttle response.

The final step was designing a custom battery case and mounting system. I wanted a 3D-printed enclosure that was both lightweight and strong enough to handle the rough conditions of city riding.

I began by modeling the 14"-long 16s3p pack and its BMS, then built the enclosure geometry around them. Since my printer can only handle 10" lengths, I split the case into two interlocking sections that could be super-glued and bolted together for rigidity.

To secure everything to the bike, I designed matching clamp brackets with a 0.5" circumscribed hex profile on the back. These mount around the square seat tube using long 1/4-20 bolts, keeping the battery locked firmly in place.

(Design image below.)

With the enclosure printed on the Bambu, I wired the entire system following my schematic. The key step was matching each motor phase wire to its corresponding Hall-effect signal lead to ensure proper commutation.

Connectors used:

• Phase wires: 4 mm bullet connectors

• Battery input: XT-60

• Hall sensor: JST-SM 5-pin

• Throttle: JST-SM 3-pin

• Ignition: JST-SM 3-pin + spade terminal

I chose these connectors for their low cost and versatility. XT-60s are reliable for currents under ~60 A, and the JST-SM series is common in many Chinese e-mobility products, with simple but secure latch mechanisms that hold up well to vibration. Since this was my first full build, using inexpensive, easy-to-replace connectors made the connection process much simpler. For future versions, I plan to upgrade the phase connections to MT60 plugs for higher current capacity and a more robust, integrated 3-pin form factor.