QS138 & QS165 Mid Motor Battery Selection Guide
QS138 & QS165 Mid Motor Battery Sizing Guide
Eliminate voltage sag, thermal cut-offs, and BMS trips. Match continuous DC discharge current and Smart BMS thresholds specifically for high-kW QS138 & QS165 mid-drive motor builds.
Interactive Controller & Battery Matcher
Fardriver ND72550 Setup Profile
- Target Motor: QS138 70H V1 / V2 or QS165
- Required Battery BMS: 180A Continuous / 350A Peak
- Recommended Cell Model: Samsung 50S (High Output)
- Cable Gauge Requirement: 8AWG High-Temp Silicone
- Main Discharge Connector: QS8 Anti-Spark Connector
DC Battery Current vs Phase Current Ratio
Phase current drives motor torque at low speed, while DC current is the actual power drawn from the pack.
QS Mid Motor Power Configuration Tiers
72V 30Ah / 40Ah (120A BMS)
Samsung 50G high-density cells. Ideal for QS138 70H motors running under 100A DC battery draw for street commuting.
72V 40Ah / 50Ah (180A BMS)
Samsung 50S high-discharge cells. Zero voltage sag under heavy throttle bursts on QS138 90H / QS165 trail setups.
72V 50Ah / 60Ah (220A BMS)
Heavy-duty steel armor casing with 220A continuous Smart BMS. Handles max phase current output without thermal throttling.
84V 40Ah / 50Ah (250A BMS)
Ultra high RPM top speed architecture. Compatible with VESC 84450 and Fardriver 84550 extreme race controllers.
Phase Current vs DC Battery Draw
High phase-current controllers draw intense DC battery current during rapid throttle acceleration:
- Fardriver ND72550 (550A Phase): Draws approx. 150A-180A DC current from battery. Requires at least 180A continuous BMS.
- Fardriver ND72800 (800A Phase): Draws up to 220A DC current. Pair with Samsung 50S cells to prevent cell thermal overload.
- VESC 75300 / 84450: Pair with Smart Bluetooth BMS for live temperature telemetry monitoring.
Connectors & Wiring Standards
High continuous current demands heavy-gauge silicone wire and anti-spark plugs:
- QS8 Anti-Spark Connector: Standard on BOOANT QS mid-motor packs (handles 180A+ continuous without terminal arc pitting).
- 8AWG High-Temp Wire: Ultra-flexible copper silicone cables for tight chassis routing.
- Smart BMS App: Real-time Bluetooth monitoring of cell voltages and BMS MOSFET temperatures.
Frequently Asked Questions
Q: What is the difference between DC current and Phase current?
A: Phase current is the AC current sent from the controller to the motor windings creating low-speed torque. DC current is the actual current drawn from the battery. A controller outputting 500A phase current may only draw 150A-180A DC current from the pack.
Q: Why is Samsung 50S recommended for QS138 90H builds?
A: QS138 90H mid motors deliver huge torque under heavy load. Samsung 50S cells support up to 25A-35A continuous discharge per cell, maintaining stable voltage without excessive thermal buildup.
Q: Can I request custom battery dimensions for my swingarm frame?
A: Yes! Most QS138 builds use custom-built frames or converted dirt bike chassis. Measure your clear internal space and submit your dimensions via our Custom Battery Form.
