The Motor Controller is the power electronics unit that converts the battery's DC into the three-phase current the motor needs, and it is also the device that decides how much torque a given throttle position requests. Two vehicles with the same motor and battery can feel completely different because their Controllers are programmed differently. Commutation method, current limits, Throttle Mapping and Regenerative Braking strategy all live in the controller, which makes it a legitimate item to specify rather than a black box.

What does the controller actually do?

It measures rotor position (via Hall sensors or by sensorless estimation), decides the timing and amplitude of the phase currents, switches its MOSFETs or IGBTs accordingly, and enforces the limits requested by the BMS and by its own temperature sensors. It also handles the throttle signal, brake inputs, fault detection and, on many vehicles, CAN communication with the display and BMS.

Because it sits between the battery and the motor, the controller is where most of the Drivetrain's behaviour is defined: maximum phase current, how quickly torque builds, when Regeneration engages, what happens at low State of Charge, and how the vehicle behaves when a fault is detected. A controller fault can look like a battery or motor problem, so diagnostics should start there.

What is the difference between square-wave and sine-wave drive?

Older or simpler controllers use six-step trapezoidal commutation, sometimes called square wave. It is cheap and robust but produces torque ripple and audible whine, particularly at low speed. Sine-wave drive shapes the phase currents more smoothly, reducing noise, vibration and low-speed cogging, which is why it is common on road-going scooters where refinement matters.

Field-oriented control, or FOC, goes further: it mathematically transforms the three-phase currents into torque-producing and flux-producing components and controls them independently, usually with a fast current loop. The result is smoother torque, better efficiency across the speed range and finer control of regeneration. FOC requires more processing and accurate rotor position estimation, but is now standard on better electric two-wheelers.

• Trapezoidal: simple and cheap, but noisier with more torque ripple.
• Sine Wave: smoother and quieter, especially at low speed.
• FOC: independent torque and flux control, good efficiency and controllable regeneration.
• Sensorless estimation removes Hall sensors but can be weaker at a standstill under load.

Controller settings can form part of the approved vehicle type. Do not change locked parameters without confirming the effect on the CoC.

How does throttle mapping change the ride?

A throttle map is the relationship between grip position and requested torque or current. A linear map is predictable; a progressive map gives fine control at small openings for manoeuvring and reserves full current for larger openings. Many vehicles add ride modes that change the map, cap top speed or limit peak current to extend range.

For a Delivery Fleet, the low-speed part of the map matters more than the headline top speed. An abrupt map makes a loaded tricycle jerky in traffic and tyre wear higher, while a well-shaped one makes it easy to manoeuvre in a warehouse. Ask whether the map is configurable by the dealer, and whether any speed limiter is part of the approved type rather than an unapproved aftermarket setting. Models such as LZ2000 EEC electric motorcycle and ZYF-800 EEC scooter should have their ride modes documented in the technical file.

How is regenerative braking controlled?

When the wheel drives the motor faster than the commanded speed, the controller can operate the motor as a generator and push current back into the battery, subject to the BMS charge-current limit. The controller decides when and how strongly to do this based on throttle position, brake inputs, wheel speed and state of charge. Regeneration is usually reduced or disabled when the pack is full, cold or at a high state of charge.

On a two-wheeler, stability and grip limit how much deceleration can come from the rear wheel, so regeneration complements rather than replaces the friction brakes. A poorly tuned system can feel like the bike is dragging or suddenly releasing, which is uncomfortable for a new rider. Ask for a description of the regen strategy and whether it can be adjusted for rider preference.

What should a buyer ask the supplier?

Request the controller's continuous and peak phase current, battery-side current limit, commutation method, sensor type, ingress rating, operating temperature range and derating behaviour, communication protocol, fault-code list, and whether parameters are field-configurable. Ask which settings are locked because they form part of the type approval.

Also ask about spare parts and service tooling. A controller that can only be diagnosed with a factory tool unavailable to the dealer network will create long downtime for a fleet. Confirm that documentation covers fault codes and that replacement units are matched to the exact motor and battery combination. Technical questions can be routed through the technical enquiry channel, and Hub Motor vs Mid-Drive Motor in Electric Motorcycles explains how the controller's current limit interacts with the motor's continuous rating.

Frequently asked questions

Is FOC always better than a sine-wave controller?

FOC generally gives smoother torque, better efficiency and finer control of regeneration, but implementation quality matters more than the label. A well-tuned sine-wave controller can feel better than a poorly tuned FOC unit.

Can I increase power by reprogramming the controller?

Technically sometimes, but it may exceed the battery's or motor's ratings, invalidate the type approval and change the legal vehicle category. Any change to approved parameters should be confirmed against the CoC before it is made; see Hub Motor vs Mid-Drive Motor in Electric Motorcycles for why the rated figure matters.

Why does regenerative braking feel weaker with a full battery?

The BMS limits charge current when the pack is full, cold or at a high state of charge, so the controller reduces regeneration to avoid overCharging. Friction brakes take over; this is normal protective behaviour.

What is a Hall sensor and why does it matter?

Hall sensors report rotor position to the controller at low speed, helping with smooth starts from a standstill. Sensorless designs estimate position from back-EMF, which works well once the motor is spinning but can be less precise at zero speed under load.

Do different ride modes change range?

Yes, indirectly. A mode that caps current and speed reduces aggressive acceleration and peak loads, which usually lowers consumption. The effect depends on how the rider actually uses the vehicle; see Continuous Rated Power vs Peak Power for how drivetrain choices interact with energy use.

Key takeaways

• The controller defines current limits, torque delivery, regeneration and fault handling, not just on/off power.
• FOC and sine-wave drive reduce noise and torque ripple compared with trapezoidal commutation.
• Throttle mapping has a larger effect on low-speed rideability than top-speed figures.
• Regeneration is limited by BMS charge acceptance and two-wheeler stability.
• Confirm which parameters are part of the approved type before changing any settings.

Treat the controller as part of the specification: ask for current limits, commutation method, ride modes, regen strategy, fault codes and service tooling. For how its current cap relates to the motor's rated power see Hub Motor vs Mid-Drive Motor in Electric Motorcycles, and for how drivetrain architecture shapes the load it drives see Continuous Rated Power vs Peak Power. Model-specific controller documentation can be requested through the technical enquiry channel.