This reference covers high-current battery discharge connectors and leads on ONYX systems: QS8, SB50, and larger QS-series options. Connector ratings do not establish the safe current of the whole battery, BMS, wire, or installation. Verify the complete current path and disconnect the battery before work.
Dual outputs or leads are not approval to parallel independent batteries. See ONYX Parallel Battery Risks. Charging connector pinouts are in XLR, XT60, and XT90 Charging Connectors.
Discharge Connectors 72V
High-current connectors transfer power between battery and controller.
- Higher current than XLR
- Sensitive to installation quality
Battery leads affect:
- Heat
- Voltage drop
- Durability
- Current delivery
QS8 Connector (Soldered - 6 AWG)
Overview
- Anti-spark connector
- High current design
- Uses 6 AWG stranded copper
Tools & Materials
- High wattage iron
- Solder
- Heat shrink
- Flux (optional)
- Clamp
Wire Preparation
- Strip cleanly
- Twist strands
- Optional pre-tin
Soldering Process
- Pre-heat cup
- Add solder
- Insert wire
- Heat until flow
- Fully fill cup
Inspection
- Smooth joint
- No exposed strands
- No movement
Important Notes
- Install heat shrink first
- 6 AWG requires high heat
- Avoid cold joints
Video - How To Solder a QS8 Connector
SB50 Connector Crimp 8 AWG
Overview
- Anderson connector
- Modular design
- Uses 8 AWG wire
Tools & Materials
- Proper crimper
- Contacts
- Housing
Wire Preparation
- Strip clean
- Do not tin
Crimping Process
- Insert wire
- Use correct die
- Perform single crimp
Inspection
- Pull test
- No loose strands
- Proper deformation
Housing Installation
- Insert until click
- Verify orientation
- Confirm lock
Important Notes
- Do not solder
- Poor crimps increase heat
Video - How To Crimp a SB50 Connector
Connector Scaling Overview
| Connector | Wire | Continuous | Peak |
|---|---|---|---|
| SB50 | 8 AWG | 50a | 70a |
| QS8 (8 AWG) | 8 AWG | 100a | 120a |
| QS8 (6 AWG) | 6 AWG | 150a | 180a |
Battery Lead Upgrade
Controller upgrades require QS8 6 AWG 14" leads.
Battery Lead Comparison
| Connector | Wire | Length | Amps | Peak |
|---|---|---|---|---|
| SB50 | 8 AWG | 18" | 50a | 70a |
| QS8 | 8 AWG | 18" | 100a | 120a |
| QS8 | 6 AWG | 14" | 150a | 180a |
Battery Lead ONYX RCR LTD
Comes stock with QS8 6 AWG 14".
QS Connector Burnout and Thermal Behavior
The QS8, QS9, QS10, and QS12 connectors’ 5 ohm resistance is insufficient for anti-spark control at higher voltages.
- Causes inrush “snap”
- Leads to connector erosion
Inrush Mitigation
- Connect at an angle (positive first)
- Use 15 mΩ pre-charge resistor
Thermal Behavior
- 150°F is normal
- Heat increases resistance
- Reduces efficiency
Heat spreads to:
- Terminals
- Controller leads
- BMS
- Enclosure
Thermal Monitoring
Use a thermal camera:
- Battery leads
- Battery
- Controller
- Motor
High-Load Testing Warning
Pushing battery lead wires to their limits is an art - one with complex processes that can’t be ignored. You’re riding the edge of setting the wire on fire without actually lighting it up.
- Take detailed notes during testing
- Perform testing in winter when possible
- Account for higher summer temperatures
Battery Lead Length
Wire length affects resistance, heat, and performance.
- Shorter = lower resistance
- Material and construction matter
Recommended:
- Silicone OFC wire
- Electrical joint compound
- Proper soldering and crimping
- PET sleeving
Battery Lead Amp Limits
Wire Limits
| Gauge | Rated | 18" | 6" | Temp/Max |
|---|---|---|---|---|
| 8 AWG | 85a | 135a | 150a | 150°F/400°F |
| 6 AWG | 120a | 150a | 175a | 150°F/400°F |
| 4 AWG | 145a | 185a | 210a | 150°F/400°F |
| 3 AWG | 190a | 230a | 255a | 150°F/400°F |
Battery Lead Bigger Configurations
Battery Lead Ratings
| Plug | Wire | Length | Amps | Peak | Plug Max | Wire Max |
|---|---|---|---|---|---|---|
| QS8 | 8 AWG | 14" | 100a | 130a | 300°F | 400°F |
| QS8 | 6 AWG | 14" | 150a | 200a | 300°F | 400°F |
| Dual QS8 | 6 AWG | 12" | 300a | 400a | 300°F | 400°F |
| QS9 | 6 AWG | 12" | 160a | 220a | 300°F | 400°F |
| Dual QS9 | 6 AWG | 12" | 320a | 440a | 300°F | 400°F |
| QS10 | 4 AWG | 10" | 210a | 270a | 300°F | 400°F |
| QS12 | 3 AWG | 6" | 250a | 320a | 300°F | 400°F |
Dual Battery Leads
Dual leads depend on battery capability.
Dual Battery Lead Rating
| Rating | Cell Amps | Internals | Benefit |
|---|---|---|---|
| 1 | 10a | Sm / Med | No |
| 2 | 15a | Sm / Med | No |
| 3 | 25a | Sm / Med | No |
| 4 | 45a | Large | Yes |
| 5 | 60a | Large | Yes |
QS8 Discharge Connector
QS8 connectors are commonly used with 6 AWG wires and are a compact high-current alternative to the stock SB50 connector.
Specifications
- Maximum Wire Size: 6 AWG
- Compatible Wire Sizes: 8 AWG to 10 AWG
- Temperature Range: -20°F to +300°F
- Metal Material: Pure Gold-Plated Brass
- Plastic Material: Nylon Reinforced with Fiber
- Flame Retardant Rating: UL94 V0
- Rated Voltage: DC 500V
- Peak Current: 180A
- Continuous Current: 110A
- Resistance: 5 ohm
- Recommended Usage: Up to 1,000 cycles
QS9 Discharge Connector
The QS9 connector is available in multiple configurations. The variation best suited for an ONYX is the QS9-L.
Specifications
- Maximum Wire Size: 6 AWG
- Compatible Wire Sizes: 4 AWG to 6 AWG
- Temperature Range: -20°F to +300°F
- Metal Material: Pure Gold-Plated Brass
- Plastic Material: Nylon Reinforced with Fiber
- Flame Retardant Rating: UL94 V0
- Rated Voltage: DC 500V
- Peak Current: 220A
- Continuous Current: 160A
- Resistance: 5 ohm
- Recommended Usage: Up to 1,000 cycles
QS10 Discharge Connector
The compact QS10 variation without the center bus pins that best suits an ONYX is the QSP10P-L.
Specifications
- Maximum Wire Size: 4 AWG
- Compatible Wire Sizes: 4 AWG to 6 AWG
- Temperature Range: -20°F to +300°F
- Metal Material: Pure Gold-Plated Brass
- Plastic Material: Nylon Reinforced with Fiber
- Flame Retardant Rating: UL94 V0
- Rated Voltage: DC 500V
- Peak Current: 270A
- Continuous Current: 210A
- Resistance: 5 ohm
- Recommended Usage: Up to 1,000 cycles
QS12 Discharge Connector
The QS12-M is the variation best suited for high-current ONYX builds.
Specifications
- Maximum Wire Size: 4 AWG
- Compatible Wire Sizes: 3 AWG to 4 AWG
- Temperature Range: -20°F to +300°F
- Metal Material: Pure Gold-Plated Brass
- Plastic Material: Nylon Reinforced with Fiber
- Flame Retardant Rating: UL94 V0
- Rated Voltage: DC 500V
- Peak Current: 320A
- Continuous Current: 250A
- Resistance: 5 ohm
- Recommended Usage: Up to 1,000 cycles
Discharge Port Charging
All ONYX batteries since 2018 support charging through the discharge port.
- Requires charger connector modification to SB50 or QS8
- Functions similarly to regenerative braking current flow
Charging behavior:
- 15A-20A is acceptable for larger batteries
- Higher sustained amperage reduces cycle life
Discharge Port BMS Charging Cap
ONYX batteries are limited by their BMS in terms of the maximum amperage they can be charged from the discharge port.
| Model | BMS Amps Cap | Theoretical Amps |
|---|---|---|
| ONYX 23AH | 10a | 24a |
| ONYX 41AH HD | 10a | 45a |
| ONYX 41AH EK | 10a | 37a |
| ONYX 45AH | 10a | 45a |
| AMORGE | 20a | 45a |
Adapter Warning
- Do not convert XLR / XT60 / XT90 to SB50 or QS8 using adapters
Final Advice
Connector reliability depends on installation, cleanliness, and system limits.
- XLR requires regular cleaning and protection
- XT improves charging durability
- QS8 depends on proper soldering
- SB50 depends on correct crimping
- Respect BMS charging limits
- Poor connections increase resistance and heat
- XLR is for charging only