ONYX Power Delivery Explained (Voltage, Current, and Torque)

This page is part of the ONYX Platform Guide

Intro

Understanding how power is delivered in an ONYX system is the foundation for understanding performance, efficiency, and heat.

This is not just about how much power the bike makes. It is about how that power is created, controlled, and translated into torque at the wheel.

This post explains how energy moves through the system, how voltage and current behave, and how the controller and motor work together to produce real-world acceleration and speed.

For how this applies specifically to the 80V platform, see:

• 80V ONYX (What Changes and Why It Matters)

Quick Summary

• Voltage determines top speed
• Current determines torque and acceleration
• The controller converts DC battery power into three-phase AC
• Phase current inside the motor is higher than battery current
• Resistance creates heat and reduces efficiency
• Power delivery is shaped by both hardware and control logic

Simple Overview

At its core the ONYX drivetrain works like this:

• The battery stores energy in lithium cells
• The controller converts DC power into three-phase AC
• The motor converts electrical energy into torque
• The DC-DC converter powers the 12V electronics
• The charger converts wall AC into battery DC
• During braking, regeneration sends energy back to the battery

Everything on the bike depends on this energy flow.

Electrical Paths Inside the Bike

Three electrical systems operate simultaneously.

High-voltage drivetrain:

• Battery → Controller → Motor → Rear wheel

Low-voltage accessory system:

• Battery → DC-DC converter → 12V accessories

Charging path:

• Wall outlet (AC) → Charger → Battery

Core Electrical Quantities

Ohm’s Law

Every conductor in the bike follows:

V = I × R

Why it matters:

• High current magnifies small resistance
• Resistance converts power into heat
• Good wiring and connectors improve efficiency

How the Battery Produces High Power

Each lithium cell operates between roughly:

• 4.2 V fully charged
• 3.6-3.7 V nominal
• ~3.0 V near empty

To power the bike, cells are combined in series and parallel groups.

Series connections (voltage)

22 cells × ~3.6 V ≈ 80 V nominal

Parallel connections (current)

Parallel groups share the current load and increase total available current.

Power Equation

Electrical power is:

P = V × I

Even small voltage changes still allow large power output because current capability remains high.

The Motor Controller

The controller is a high-power inverter.

It converts steady DC from the battery into three precisely timed AC waveforms using high-speed MOSFET switching and pulse-width modulation.

Its internal control system manages:

• Rotor position feedback
• Current control loops
• Torque commands
• Thermal limits
• Voltage limits

Hall Sensors vs Encoders

To produce smooth torque, the controller must know the rotor position.

Hall sensors:

• Standard on e-bikes
• Reliable
• Simple
• Excellent for real riding

Encoders:

• Extremely precise
• Used in robotics and industrial systems
• More complex and expensive
• Rare in hub motors

For hub motors like the ONYX RCR, Hall sensors provide the ideal balance of simplicity and performance.

How the Motor Produces Torque

The hub motor contains:

• Stator windings (electromagnets)
• Rotor magnets

Three-phase AC creates a rotating magnetic field which pulls the rotor forward.

Key relationships:

Battery current and motor phase current are not the same.

The controller converts voltage into higher phase current at low speed, allowing strong torque.

Current, Torque, and Acceleration

Acceleration is current-limited.

Top speed is voltage-limited.

Back-EMF and Speed Limit

As the motor spins faster, it generates back-EMF opposing the battery voltage.

Eventually:

Motor back-EMF ≈ battery voltage

At that point torque falls and the bike reaches its maximum speed.

Low-Speed vs High-Speed Power Delivery

Power delivery changes as motor speed increases.

To simplify this, imagine a motor with a maximum speed of 1000 RPM.

Low speed range (0 to ~500 RPM)

At lower speeds:

• back-EMF is low
• the controller can push high phase current into the motor

This means:

• current determines torque
• acceleration is strongest in this range
• the system can multiply torque through phase current

This is where:

• launches happen
• initial acceleration is defined
• controller current limits matter most

In practical terms:

low speed performance is current-limited

High speed range (~500 to 1000 RPM)

As speed increases:

• back-EMF rises
• it begins to oppose battery voltage

At this point:

• the controller can no longer increase current freely
• available torque begins to drop

Now:

• voltage becomes the limiting factor
• higher voltage allows higher RPM before torque falls off

In practical terms:

high speed performance is voltage-limited

Why torque drops at speed

As the motor approaches top speed:

• motor back-EMF approaches battery voltage
• effective voltage across the windings decreases
• current drops
• torque drops

This is why acceleration fades at higher speeds even at full throttle.

Field weakening and extended top speed

Field weakening (also called flux weakening) is a controller technique used to push the motor beyond its natural speed limit.

It works by:

• weakening the magnetic field inside the motor
• reducing effective back-EMF

This allows:

• higher RPM beyond the normal voltage limit

However, there are tradeoffs:

• reduced torque
• lower efficiency
• increased heat

In practice:

• field weakening increases top speed
• but makes the motor feel softer at high speed
• and increases thermal load

Real-world takeaway

Power delivery is not constant across speed.

• Low speed = current dominates → strong torque
• High speed = voltage dominates → limits top speed
• Field weakening = extends speed at the cost of efficiency and torque

Understanding this explains why:

• bikes feel strongest off the line
• acceleration fades at higher speeds
• higher voltage systems hold speed better

Power Flow Through the System

Electrical input power:

P = V × I

Energy moves through stages:

Battery → Controller → Motor → Wheel

Losses occur in:

• Controller switching
• Motor copper losses
• Magnetic losses
• Bearings and tires

Moderate cruising is typically the most efficient operating point.

Why the Same Bike Can Feel Completely Different

Two ONYX builds can use the same platform, the same voltage, and even similar advertised power, but deliver power very differently in real-world use.

This can happen with:

• stock vs modified builds
• different battery packs
• different controllers or tuning
• original vs aftermarket or clone components

Power delivery is not defined by a single specification. It is defined by how the entire system performs under load.

Battery cell quality and behavior

Not all lithium cells perform the same, even within the same chemistry.

Two packs may both be NMC, but differ in:

• internal resistance
• voltage sag under load
• thermal stability
• discharge capability

A higher quality cell will:

• hold voltage better under load
• deliver current more consistently
• generate less heat at the same power level

A lower quality or more energy-dense cell may:

• sag more under acceleration
• reduce effective power output
• increase heat generation

Pack construction and current delivery

Beyond the cells themselves, pack design matters.

Differences include:

• parallel group size
• busbar design
• weld quality
• overall internal resistance

These factors affect how easily current can flow from the battery to the controller.

Even small increases in resistance can reduce performance under load.

Voltage Sag and Real Power

Under load, battery voltage does not remain constant.

As current increases:

• voltage drops
• effective power decreases

This is known as voltage sag.

Higher sag results in:

• reduced acceleration
• lower effective power
• increased heat

Lower sag results in:

• stronger sustained acceleration
• more consistent performance
• better efficiency

Real-world power is determined by loaded voltage, not resting voltage.

Controller Tuning and Throttle Mapping

Power delivery is not only determined by hardware. The controller defines how that power is applied.

Two identical systems can behave very differently depending on:

• throttle curve mapping
• current ramp rate
• torque limits at different speeds
• smoothing and filtering

An aggressive tune may:

• deliver current quickly
• feel sharp and immediate
• increase stress and heat

A smoother tune may:

• ramp power more gradually
• feel more controlled
• reduce thermal spikes

Phase Current and Torque Multiplication

The controller does not send battery current directly to the motor.

At lower speeds, it converts voltage into higher phase current.

This allows:

• strong torque at low speed
• high acceleration from a stop

Motor phase current can be significantly higher than battery current.

Controller design and configuration directly affect how much torque is produced.

Peak Power vs Sustained Power

Power figures are often quoted as peak numbers, but real-world riding depends on sustained power.

Peak power:

• short duration
• influenced by controller limits

Sustained power:

• limited by heat
• limited by battery performance

A system that produces high peak power but fades quickly will behave very differently from one that maintains consistent output.

Why differences become obvious over time

Short test rides can hide real differences between builds.

Under sustained riding, small inefficiencies begin to compound.

As time under load increases:

• heat builds in the battery, controller, and motor
• voltage sag becomes more pronounced
• resistance increases with temperature
• efficiency drops

A higher quality system will:

• maintain voltage more consistently
• hold power under continuous load
• manage heat more effectively
• feel stable even after extended riding

A lower quality system may:

• lose power as temperature rises
• feel weaker after repeated acceleration
• become less responsive over time
• heat soak and struggle to recover

Motor quality and component differences

Motor design and build quality also influence power delivery.

Differences between original and lower-quality or clone motors can include:

• magnet quality and temperature stability
• winding quality and resistance
• internal losses
• thermal handling

These differences affect:

• torque production
• efficiency under load
• how quickly the motor heats up

A lower quality motor may still function, but:

• produce less torque for the same input
• generate more heat
• lose performance faster under sustained load

Aftermarket parts: improvement or regression

Aftermarket upgrades can significantly improve performance, but they can also make a system worse if parts are not chosen carefully.

Higher quality components can:

• improve power delivery
• reduce voltage sag
• increase efficiency
• handle heat more effectively

However, not all aftermarket parts are equal.

In some cases:

• lower-quality or cloned components are used
• parts are mislabeled or do not meet their claimed specifications
• components are not matched properly to the rest of the system

This can result in:

• reduced real power output
• increased heat
• inconsistent performance
• faster performance drop under load

A poorly matched or lower-quality aftermarket setup can perform worse than a well-balanced stock system.

System Resistance and Efficiency

Every part of the system introduces resistance:

• battery internal resistance
• wiring and connectors
• controller switching losses
• motor windings

As current increases:

• losses increase
• heat increases
• efficiency decreases

Small differences in resistance can result in noticeable performance changes.

Small inefficiencies that are not visible in specs become significant under load.

For how power delivery translates into heat and real-world thermal behavior, see:

• ONYX Motor Heat Explained

Why Similar Bikes Can Have Very Different Outcomes

It is common to compare two bikes that appear nearly identical:

• similar size and weight
• similar voltage
• similar advertised power

On paper, they should perform the same.

In practice, they often do not.

Acceleration and racing scenarios

When two bikes are ridden or raced side by side, the outcome can be very different even when the specs look similar.

One build may:

• launch harder
• pull ahead under load
• maintain power through acceleration

The other may:

• feel strong initially but fall behind
• lose power as speed increases
• struggle to maintain output under load

Sustained riding and range scenarios

The same pattern shows up over longer rides.

Two builds may start at similar performance levels, but diverge over time.

One system may:

• maintain consistent power
• manage heat effectively
• deliver stable performance over distance

The other may:

• gradually lose power
• build heat more quickly
• become less efficient as the ride continues

This directly affects:

• usable range
• average speed
• overall ride consistency

Why this happens

These differences are the result of:

• voltage stability under load
• current delivery capability
• motor efficiency
• thermal behavior over time

Small inefficiencies that are not visible in specs become significant under load.

Why Spec Comparisons Often Fall Short

When people compare electric bikes, the focus is usually on:

• voltage
• peak power numbers
• advertised performance
• short impressions from videos or quick rides

These comparisons are incomplete.

They do not show:

• how the system performs under sustained load
• how voltage behaves under acceleration
• how heat affects performance over time
• how consistent the system is during sustained riding

Specs are not wrong, but they do not tell the full story.

Practical takeaway

Real comparison requires looking at:

• how the system delivers current
• how stable voltage remains under load
• how the system behaves over time

Understanding power delivery is what turns a basic comparison into an informed decision.

Why Real-World Performance Is Often Discovered, Not Tested

Most riders do not fully test performance before forming conclusions.

Instead, performance is experienced over time.

This shows up in common ways:

• range is not fully tested until a long ride forces it
• sustained power is not noticed until performance begins to fade
• heat behavior is only observed after extended use

Short rides and first impressions do not reveal these behaviors.

Why this matters

Early impressions are based on:

• initial acceleration
• responsiveness
• fresh system performance

These do not represent:

• sustained load
• rising temperatures
• long-term efficiency

Because of this, two systems that feel similar at first can diverge significantly during sustained riding.

Key takeaway

Performance is revealed:

• under sustained load
• over longer rides
• as the system heats and stabilizes

Understanding power delivery explains these outcomes before they are experienced.

DC-DC Converter and Accessories

The DC-DC converter steps the main battery voltage down to 12V.

It powers:

• Headlight
• Brake light
• Turn signals
• Horn
• Display electronics

This conversion uses high-frequency switching for efficiency.

Regenerative Braking

During regen:

Motor → Controller → Battery

The motor becomes a generator and produces braking torque.

Effects include:

• Energy recovery
• Reduced brake wear
• Improved downhill control

How the Charger Works

The charger converts household AC into high-voltage DC through several stages:

1. Rectification
2. Power factor correction
3. High-frequency switching
4. Transformer conversion
5. Output rectification
6. Voltage and current regulation

CC/CV Charging

Lithium batteries charge in two phases.

Constant Current (CC)

• Charger supplies fixed current
• Voltage rises

Constant Voltage (CV)

• Voltage held at maximum
• Current tapers

Battery Cell Balancing

The battery management system (BMS):

• Monitors each cell group
• Bleeds down higher groups
• Keeps the pack balanced

Balancing mainly occurs near full charge during the CV phase.

Heat Generation

Primary heat sources include:

• Controller switching losses
• Motor copper losses
• Battery internal resistance
• Wiring resistance

Doubling current roughly quadruples resistive heating.

Final Takeaway

Power delivery in an ONYX system is not defined by a single number.

• Voltage enables speed
• Current creates torque
• The controller manages how power is applied
• The motor converts electrical energy into motion
• Resistance turns unused energy into heat

Real-world performance is defined by how well the system delivers and sustains power under load.