QS138 & QS165 Mid Motor Battery Selection Guide
QS138 & QS165 Mid Motor Battery Sizing Guide
Match battery current to controller current first. Phase current is not battery current. A controller that outputs high phase current can still draw much less from the battery, and a BMS that is too small will trip under hard throttle.
Quick answer: Tell us your controller model and its battery current limit first, not just its phase current. BMS continuous must be at or above that battery current, with headroom. Then check your controller max voltage label before you choose a high-voltage tier.
Controller & Battery Matching Reference
Fardriver ND72550
- Target MotorQS138 70H / QS165
- Required BMS180A Continuous
- Cell ChoiceSamsung 50S / 50G
- Cable Gauge8AWG Silicone
- Main ConnectorQS8 Anti-Spark
Fardriver ND72800
- Target MotorQS138 90H V2 / Heavy
- Required BMS220A Continuous
- Cell ChoiceSamsung 50S Extreme
- Cable Gauge6AWG Silicone
- Main ConnectorQS10 Anti-Spark
VESC 75300 / 84450
- Target MotorQS138 70H / High Speed
- Required BMS200A Smart BMS
- Cell ChoiceSamsung 50S, Bluetooth
- Cable Gauge8AWG Silicone
- Main ConnectorQS8 / QS10 Anti-Spark
Sabvoton 72150 / 72200
- Target MotorQS138 70H V1 / Mild
- Required BMS150A To 200A, Check Model
- Cell ChoiceSamsung 50G / 50S
- Cable Gauge8AWG Silicone
- Main ConnectorQS8 Anti-Spark
QS Mid Motor Power Configuration Tiers
72V 30Ah / 40Ah, 120A BMS
Samsung 50G cells. For QS138 70H motors with battery draw under 120A, for street commuting. If your draw is higher, choose a higher tier.
72V 40Ah / 50Ah, 180A BMS
Samsung 50S cells. Less voltage sag than 50G at the same current, for QS138 90H and QS165 trail setups.
72V 50Ah / 60Ah, 220A BMS
Steel armor casing with 220A Smart BMS. Gives headroom for high phase controllers, check temperature under hard use.
72V Nominal, 84V Full, 250A Peak
For VESC 84450 and Fardriver controllers that accept 84V full charge. Do not use a 24S Li-ion pack, 100.8V full, with an 84V-max controller. Check your controller max voltage label first.
Phase Current vs DC Battery Draw
Phase current is motor current, DC current is battery current. They are not the same.
- Fardriver ND72550, 550A Phase: Draws approx. 150A to 180A DC. BMS continuous should be at or above that draw, with headroom.
- Fardriver ND72800, 800A Phase: Draws up to 220A DC. Cell parallel count must also support that current, not just cell model.
- VESC 75300 / 84450: Use Smart Bluetooth BMS and check live temperature, and check max voltage label, 75300 is 75V class, 84450 is 84V class.
Connectors & Wiring Standards
Match connector and wire to BMS current.
- QS8 Anti-Spark: For tiers up to 180A class.
- QS10 Anti-Spark: For 220A plus tiers.
- Wire: 8AWG up to 180A class, 6AWG for 220A plus class. Tell us your BMS current when ordering.
- Smart BMS App: Check cell voltages and BMS temperature in real time.
Frequently Asked Questions
Q: What is the difference between DC current and Phase current?
A: Phase current goes from controller to motor windings and makes low-speed torque. DC current is what the battery actually delivers. A 500A phase controller may only draw 150A to 180A DC from the pack.
Q: Why is Samsung 50S recommended for QS138 90H builds?
A: 90H motors make high torque under load. 50S cells hold voltage better at high current than 50G, but total current also depends on parallel count, so check Ah and P count, not just cell model.
Q: Can I request custom battery dimensions for my swingarm frame?
A: Yes. Measure clear internal space, then submit those dimensions in the custom form, with your tier, controller model, and battery current limit.
