This post is a practical technical reference for the 72V ONYX 41Ah battery used on the RCR platform.
It covers how the pack behaves as it ages, safe current limits, BMS telemetry and balancing, charging strategy, temperature guidance, voltage sag interpretation, the discharge curve, and end-of-life thresholds. It starts with the basics and then progresses into the deeper electrical and lifecycle details that matter for tuning and reliability.
ONYX 41Ah 72V Battery Aging
The ONYX 41Ah battery pack has reached an age where reduced performance is expected. Riders will typically see shorter range, weaker acceleration, heavier voltage sag under load, and higher battery temperatures during aggressive riding, all caused by rising internal resistance in the cells.
At this point, the pack should not be pushed beyond stock Kelly controller limits. High-current modes such as SICKO MODE or FarDriver JAWS MODE can overstress aging cells, leading to rapid degradation and permanent capacity loss, with a real risk of partial or complete pack failure.
For safe operation and longevity, stay within the specified DC current, DC boost, and AC phase current limits.
ONYX 41Ah 72V DC Current and Phase
- DC Current Amps: 80A to 90A
- DC Boost Current: 90A to 100A
- AC Phase Current: 180A to 240A
ONYX 41Ah 72V Battery Management System (BMS)
Both batteries rely on a BMS to:
- Prevent over-current and short circuits
- Monitor temperature
- Balance cell groups
- Track voltage, capacity, and health
ONYX 41Ah 72V BMS Apps
ONYX 41Ah 72V What the Apps Show
- Pack voltage
- Cell voltage delta (balance)
- Battery temperature
- State of Health (SOH)
- Error history
ONYX 41Ah 72V Discharge Connector
- SB50 connector
- Discharge must be disabled in the app before connecting
- Can spark if connected live
ONYX 41Ah 72V Connecting the Charger
- Plug the charger into the wall
- Then connect the XLR to the battery
This prevents connector damage and sparking.
ONYX 41Ah Charging Times
| Battery | Charger | 0 -> 100% | 50 -> 100% |
|---|---|---|---|
| 41Ah | 5A | 10.6 h | 7.6 h |
| 41Ah | 10A | 5.4 h | 3.6 h |
Charging to 83-83.5V is faster and improves lifespan.
ONYX 41Ah 72V Reading Battery Level
| Voltage | State |
|---|---|
| 84 V | Full |
| 72 V | ~50% |
| 60 V | Empty |
Expect ~0.6V drop when the bike is powered on.
ONYX 41Ah 72V Battery Pack Basics
Both packs contain roughly 160-200 cells.
- 4.20 V per cell = full
- 3.00 V per cell = empty
ONYX 41Ah 72V Temperature Guidelines
- Ride below 60°C / 140°F
- Charge below 40°C / 104°F
- Rest 30-60 minutes after aggressive riding before charging
ONYX 41Ah 72V Safety Basics
- Avoid charging in direct sunlight
- Do not charge below 32°F or above 120°F
- Clean XLR connectors occasionally
- Stop riding if resting voltage becomes unstable
ONYX 41Ah 72V Best Charging Practice
| Use Case | Voltage |
|---|---|
| Daily riding | 78-81 V |
| Long storage | ~74 V |
| Maximum range | 83-84 V |
ONYX 41Ah 72V Charge Cycle Multipliers
| Charge Level | Life |
|---|---|
| 84 V | 1× |
| 83 V | 1.5× |
| 82 V | 2× |
| 81 V | 3× |
| 80 V | 4× |
Charging to 82V usually costs ~2 miles of range but doubles battery life.
ONYX 41Ah 72V Cell Balance
| Delta | Meaning |
|---|---|
| 0.01-0.05 V | Excellent |
| 0.05-0.10 V | Normal |
| 0.10-0.15 V | Acceptable |
| 0.15-0.30 V | Warning |
| 0.30 V+ | Severe |
High imbalance reduces range, causes early cutoffs, and accelerates aging.
ONYX 41Ah 72V Unbalanced Battery Fix
- Install the Overkill Solar BMS app.
- Open the app within 5 ft of the battery and connect to the Bluetooth device starting with HD or EK.
- Go to Settings → BMS Read.
- Change Start Voltage: 3700
- Bal. Only When Charging: OFF (grey)
- Tap BMS Write to save.
- Charge the battery to 80–83V.
- Let the battery rest for 3 days (do not ride).
- If 0.300–0.500V → repeat the rest period and monitor daily.
- If > 0.500V → ask for help in ONYX AF.
ONYX 41Ah 72V Battery Repair
Northeast Battery Systems has developed a strong reputation within the ONYX community for both repairs and custom battery work. They understand the platform in stock form and in high-performance builds, and design their packs with safety and durability as top priorities.
Kevin and his team are known for professional communication, accurate diagnostics, and consistent results. Many ONYX owners rely on them for rebuilds, upgrades, and long-term support.
Their process includes consultation, full diagnostics, honest recommendations, and clear estimates before any work begins.
- Expert consultations
- High-performance battery builds
- Battery rebuild services
- Durable metal enclosures
- Cell balancing and balance-lead repair
- Battery health diagnostics
- Performance testing and validation
- BMS swaps
- 18-month warranty
NEBS Contact Information
- Northeast Battery Systems
- Address: 200 Old County Circle, Unit 307, Windsor Locks, CT 06096
- Email: nebattsys@gmail.com
- Phone: (860) 951-1468
ONYX 41Ah 72V Voltage Sag
Voltage sag reflects internal resistance and overall pack health. Excessive sag creates heat, wastes power, and damages cells.
For a healthy 40-60Ah battery at 83+V and 60-90°F:
| Sag | Condition |
|---|---|
| 3-8V | Good |
| ~10V | Poor |
| 10-15V | Risky |
| 15V+ | High risk |
Large packs cannot hide poor cells. Two batteries with the same capacity can perform very differently depending on cell quality and internal resistance.
If sag exceeds 15V, reduce power or replace the pack.
Keep battery temperature under 122°F (50°C) if sag regularly exceeds 10V.
ONYX 41Ah 72V Discharge Curve
The 41Ah pack discharges faster near the top (above 82V) and bottom (below 66V).
Low-Voltage Reference
- 8% -> 62V
- 4% -> 61V
- 0% -> 60V
ONYX 41Ah 72V Sag Discharge Example
Example: 41Ah pack with 80A BMS in Sicko Mode, starting at 83.6V:
- Sag: 15.4V
- Output: ~18 kW
Newer 100A BMS versions can reach ~20 kW.
ONYX 41Ah 72V C-Rate and E-Rate Explained
C-rate describes discharge current relative to capacity.
- 1C -> full discharge in 1 hour
- 5C -> full discharge in 12 minutes
- 0.5C -> full discharge in 2 hours
E-rate describes discharge power instead of current.
ONYX 41Ah 72V Battery and Cell Voltage Chart
Prolonged time above 4.2V or below 2.5V causes permanent damage or thermal risk.
| Battery V | Cell V | Description |
|---|---|---|
| 90V | 4.50V | Thermal runaway risk |
| 88V | 4.40V | Thermal runaway risk |
| 85V | 4.25V | Rapid degradation |
| 84V | 4.20V | True 100% |
| 83V | 4.15V | Stock “100%” |
| 80V | 4.00V | ~80% |
| 74V | 3.70V | Storage level |
| 72.5V | 3.63V | ~50% |
| 66V | 3.30V | ~25% |
| 60V | 3.00V | Empty |
| 50V | 2.50V | Minimum |
| <50V | <2.50V | Damage occurs |
ONYX 41Ah 72V End-of-Life Threshold
If any cell group drops below 2.5 V, the battery has reached end of life and replacement is usually the safest option.
Common symptoms
- Sharp loss of usable capacity and range
- Increased voltage sag, even under light load
- Growing cell imbalance that no longer stabilizes after balancing
- Frequent BMS cutoffs during riding or charging
- Higher operating temperatures caused by rising internal resistance
Technical explanation
Below 2.5 V, lithium-ion cells begin to suffer irreversible chemical damage. Copper can dissolve from the current collectors and lithium plating can form on the electrodes. Both conditions permanently increase internal resistance and significantly raise the risk of internal short circuits and thermal instability.
Conclusion
Once a cell group reaches this voltage, repair is rarely durable or safe. Battery replacement is the most reliable long-term solution.