This guide explains how to safely evaluate a used 72V ONYX before buying.
It begins with quick verification steps and then moves into deeper inspection of the battery, electronics, and drivetrain so you can avoid expensive surprises and unreliable builds.
If you verify only one thing, make it the battery.
- Start with fast visual checks
- Confirm battery health before anything else
- Always have the owner perform a real test ride
Buy or Sell Safely
The ONYX AF Sales group is one of the safest marketplaces for used bikes and a good place to verify sellers, pricing, and known builds.
Used Buyer Caution
This post covers common scams, unsafe wiring jobs, and misleading listings from shops and private sellers.
Quick Used Bike Inspection
If you are short on time, verify these immediately before going deeper into the inspection.
| Inspection Check | What to Verify | Why It Matters |
|---|---|---|
| Proof of ownership | Seller provides documentation or receipt | Prevents purchasing stolen bikes |
| Battery health | BMS app connects and shows healthy readings (41Ah battery) | Battery is the most expensive component |
| Winter storage | Bike stored indoors during winter | Cold storage damages lithium cells |
| Wiring quality | Clean wiring with no tape bundles or exposed copper | Indicates responsible electrical work |
| Charger included | Correct charger for the 72V system | Ensures safe charging |
| Sport mode test ride | Seller rides the bike up and down the street first | Demonstrates battery, controller, and brake performance |
Watching the seller ride the bike first is important. It lets you observe how the battery, controller, and braking system behave under load.
If an ONYX cuts out during the test ride in front of you, that is a serious warning sign.
If any of these checks fail, walk away.
Non-ONYX Battery Warning
Be cautious when buying a 72V ONYX with a battery that did not originate from ONYX Motors.
Battery packs vary widely in cell quality, internal construction, and BMS configuration. While some aftermarket packs are well built, others can cause voltage sag, cutouts, or long-term reliability problems.
It is also common in the used market for battery details to be misidentified or exaggerated. Sellers may repeat information from previous owners and may not actually know the true builder, cell type, or capacity.
| Battery Source | Notes |
|---|---|
| ONYX Motors | Factory battery configuration |
| AMORGE | Known builder used in many ONYX upgrades |
| North East Battery Systems | Trusted builder within the ONYX community |
If the seller cannot clearly identify who built the battery, treat the pack as unknown and inspect the system carefully.
Most riders also never try other ONYX bikes, so they may not realize how much performance, range, or stability their setup is lacking. This makes it easy for misleading battery claims to go unnoticed.
Basic Bike Inspection
Inspect the bike in good lighting before any test ride.
| Component | What to Check |
|---|---|
| Frame | Cracks, dents, bends, or crash damage |
| Battery compartment | Rust or water exposure |
| Weld areas | Signs of stress or repair |
| Wheels | Bent rims or loose spokes |
| Wiring | Clean routing with no electrical tape bundles |
| Connectors | No exposed copper or melted connectors |
Have the seller ride the bike first and confirm the following systems operate correctly.
| System | Verification |
|---|---|
| Headlights | Fully operational |
| Brake lights | Activate correctly |
| Turn signals | Function normally |
| Regenerative braking | Engages smoothly |
| Motor sound | No grinding or clicking |
A clean bike is easy to recognize. A problem bike is expensive to fix.
Odometer Check (MPH ↔ KM/H)
Sometimes mileage is reset or the display unit is changed.
To toggle units on the ONYX display:
- Hold SET (bottom-left button) for 10 seconds
- Release the button
- Hold SET again for 10 seconds to toggle units
Large inconsistencies in mileage are a red flag.
What to Ask the Seller
| Item | Why It Matters |
|---|---|
| Two key fobs | Replacement fobs are expensive |
| Two wooden battery cover keys | Required for battery access |
| Original charger (5A or 10A) | Confirms proper charging equipment |
| Proof of purchase | Verifies legitimate ownership |
| BMS app password | Required to view battery data |
Battery Health
The battery is the most expensive component on the bike.
Always confirm:
- Battery was stored indoors during winter
- No swelling or physical damage
- Bluetooth connection to the BMS works (41Ah battery)
Battery condition determines whether the purchase is safe.
Battery Comparison
| Battery | Production Status | Typical Lifespan | Risk Level |
|---|---|---|---|
| 41Ah | Current production | Long lifespan | Lower risk |
| 23Ah | Discontinued Fall 2022 | ~2027 best case | Higher risk |
ONYX 41Ah Battery
The ONYX 41Ah battery includes a Bluetooth BMS app, allowing you to inspect cell balance and pack health directly from your phone.
Healthy readings typically include:
- Cell delta between 0.005V – 0.080V
- Stable voltage at rest
- No sudden power cutouts under load
Example BMS screen:
ONYX 23Ah Battery
The 23Ah battery does not include a Bluetooth BMS app, which means internal battery health cannot be easily verified from a phone.
This battery pack has not been produced since Fall 2022.
Key realities:
- Best-case lifespan: approximately 2027
- Poor storage dramatically shortens lifespan
- More prone to voltage sag and early cutoffs
Test method:
- Charge battery to approximately 72V
- Perform full throttle acceleration in Sport mode
- Watch for immediate power cutout or voltage collapse
If the pack shows instability, plan for replacement.
Charger
Verify the charger supplied with the bike.
| Check | What to Verify |
|---|---|
| Voltage | Correct charger for the 72V system |
| Cooling fan | Fan operates normally |
| Error lights | No fault indicators |
| Connectors | Original connectors in good condition |
Motor
Listen carefully during operation.
| Inspection Area | Problem Signs |
|---|---|
| Motor sound | Grinding or clicking noises |
| Acceleration | Uneven whine or vibration |
| Phase wires near axle | Damage or overheating |
| Hall sensor cable | Cuts, splices, or exposed wiring |
Hub motor repairs deserve extra scrutiny.
Controller
Many used bikes include aftermarket controllers.
| Parameter | What to Verify |
|---|---|
| Amp limit | Matches listing or seller claim |
| Mounting | Secure installation |
| Wiring gauge | Proper wire thickness |
| Heat damage | No burnt smell or melted insulation |
Bad controller tuning can destroy motors and batteries.
Suspension
Check both front and rear suspension components.
| Component | What to Check |
|---|---|
| Front fork | Smooth compression with no sticking |
| Rear shock | Compress smoothly without clunking |
| Seals | No visible oil leaks |
Brakes
| Component | What to Check |
|---|---|
| Brake pads | Not excessively worn |
| Rotors | No warping |
| Braking feel | Smooth braking without noise |
Electrical System
Poor wiring is a major warning sign.
| Red Flag | Meaning |
|---|---|
| Twisted wiring | Amateur installation |
| Electrical tape repairs | Temporary fixes |
| Random connectors | Non-standard electrical modifications |
| Exposed copper | Safety hazard |
Sloppy wiring often indicates deeper internal problems.
Throttle & Display
| Component | What to Verify |
|---|---|
| Throttle | Smooth response with no dead zones |
| Display brightness | Stable with no flickering |
| Acceleration response | Consistent throttle input |
Tires
Stock tire sizes for the ONYX RCR:
| Size | Notes |
|---|---|
| 2.75" × 17" | Stock |
| 3.00" × 17" | Stock |
Common tire brands used by owners:
| Brand | Notes |
|---|---|
| Mitas | Popular upgrade |
| Michelin | High grip option |
| Vuro | Budget option |
Wheels & Spokes
| Inspection | What to Check |
|---|---|
| Wheel rotation | Spin freely with no side wobble |
| Spoke tension | Spokes should feel tight |
| Rim alignment | No visible bending |
Aftermarket Parts
Aftermarket upgrades are acceptable if installed properly.
Verify:
- Installation is clean and professional
- Components are from known brands
- Seller can explain the purpose of the upgrade
- Wiring remains organized and secure
Hub motor repairs require additional inspection.
Controller Tuning
Ask the seller about controller configuration.
| Parameter | Why It Matters |
|---|---|
| Battery amps | Determines overall power draw |
| Phase amps | Impacts motor stress and torque |
| Regen strength | Excessive regen can damage components |
| Tune type | Stock or custom configuration |
Improper tuning can shorten the lifespan of both battery and motor.
Test Ride
Always perform a real test ride.
Check the following:
| Ride Behavior | What to Observe |
|---|---|
| Straight tracking | Bike should not pull to one side |
| Acceleration | Smooth and predictable |
| Vibration | No abnormal vibration |
| Throttle response | No hesitation |
Top Speed & Torque
During a Sport mode test ride verify:
- Strong acceleration
- Stable power delivery
- No sudden power dropouts
Weak power or instability can indicate battery or controller issues.
Ownership
Always require proper ownership documentation.
| Requirement | Reason |
|---|---|
| Bill of sale | Protects both buyer and seller |
| Proof of ownership | Prevents stolen vehicle purchases |
Maintenance History
Ask the seller about the bike’s history.
| Topic | What to Ask |
|---|---|
| Charging habits | How the battery was typically charged |
| Winter storage | Indoor vs outdoor storage |
| Tire replacements | Maintenance schedule |
| Electrical repairs | Past wiring or electrical work |
| Controller changes | Any tuning or controller swaps |
If something feels off, it probably is. Clean bikes appear regularly, and walking away from a questionable one can save thousands in repairs.