Build a 52V Trailhead E-Bike (Fast-Charge Ready)

Mid-drive or hub, clean wiring, serious brakes, and a charge port that mates with your CC/CV case.

Safety First

Use a pack with a BMS and a verified charge port pinout. Never bypass protection.
Add a 40–60A fuse on the battery positive, and an XT90-S anti-spark on high-current leads.
Hydraulic discs + 180–203mm rotors are strongly recommended.
Match charge voltage to chemistry: 48V (13S) ≈ 54.6V, 52V (14S) ≈ 58.8V.

What You’re Building

Battery: 48/52V (BMS) Power: 750–1000W cont. Peak: 1.2–1.8 kW Brakes: Hydraulic 180–203 mm Charge: CC/CV via case

Pick mid-drive (climbs, efficiency) or rear hub (simplicity). Both can be wired for your fast-charge case.

Parts Checklist

Motor + controller (48/52V, 20–30A), display, PAS/torque, throttle
Battery 48/52V 17–20Ah with BMS + panel-mount charge port
Hydraulic brakes 180–203mm, metal pads, good tires
Main fuse 40–60A, XT90-S anti-spark, 12–10 AWG battery leads
52→12V buck for lights/USB (optional)
Rear rack/plate for carrying the charger case

Wiring Snapshot

[ 52V Pack ]--Fuse--XT90-S--[ Controller ]--(Motor)
                   |
             (to Charge Port) --> Panel Jack (XLR/XT/SB50/RoPD)
Controller -> Display / PAS / Throttle / Brake cutoffs
12V lights -> 52V->12V Buck -> Switch

Build Steps

Fit drivetrain: mid-drive into BB (or hub into dropouts + torque arm). Set chainline with spacers.
Mount controller: airflow path, avoid tire spray. Loom cables.
Battery & fuse: strap pack; wire fuse close to +; add XT90-S to controller lead.
Charge port: panel-mount; wire to pack charge leads; label voltage & polarity.
Controls: display/PAS/throttle on bars; tune PAS levels and current limit (25–30A max typical).
Test ride: check brake cutoffs, gear under load, temps; re-torque after 20–30 km.

Range Estimator

Ballpark only; hills, wind, and tires change everything.

Battery (Wh) Average Consumption (Wh/mi) Target Reserve (%) Assist Level

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Speed vs. Wheel & Cadence

Helps pick chainring/cassette for your mid-drive cadence sweet spot.

Wheel Size (mm circumference) Cadence (rpm) Front Teeth Rear Teeth

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Fast-Charge Workflow (with the Case)

Connect charge lead → verify polarity.
Select correct profile (48V 54.6V / 52V 58.8V / per maker).
Set amps within pack limit (e.g., 4–8A).
Supervise; disconnect at target SOC (80–90% for quick turnarounds).

Don’t Do This

Charge below freezing or leave charging unattended.
Skip the main fuse or anti-spark on high-current lines.
Guess the charge pinout; meter it first.