S06P / S-KU63 torque simulation motor controller. Overvolting ebike controller

The Importance of Electric Scooter Controllers

Have you ever wondered how an electric scooter controls its speed even when receiving a constant power supply? Unlike in internal combustion engines, where the automobile’s speed is controlled by increasing or reducing the amount of fuel entering the combustion chamber, electric scooters leverage electric controllers to regulate the speed.

The controller, also referred to as an electronic speed controller (ESC), is essentially an electronic circuit that regulates the speed of the motor in an E-scooter. It directs and regulates power from the battery to the motor.

By twisting or pressing the throttle to a certain degree, a rider is principally sending signals to the controller, which signals the battery to release more or cut the amount of power being directed to the motor. And if you press the electronic brakes, the controllers cut the power supply from the battery to the motor, causing it to stop functioning and ultimately reduce the overall speed.

While they are one of the most under-appreciated parts of an electric scooter, controllers are like the brain of e-scooters. It links all other electronic components of the e-scooter, including the battery, motor, electronic brakes, throttle (accelerator), display (speedometer), speed sensors, and other components. E-scooter controllers govern various aspects of the scooter, including starting, speeding, braking, riding modes, and ultimate stopping, among other functions.

Here is a detailed look at electric scooter speed controllers with an eye on their functioning in detail, types of controllers, maintaining and repairing controllers, as well as their overall importance.

What is an Electric Scooter Controller?

The importance of electric scooter controllers is to take all the inputs from all the electric components in the scooter, i.e. battery, throttle, speed sensor, display, motor, etc., and then determine the necessary signals that should be relayed to them. For instance, when a rider twists or presses the throttle, it sends a signal to the controller, increasing the amount of current from the battery to the electric motor. current to the motor means faster propulsion of the wheels hence more speed.

In most electric scooters, controllers have an electronic braking function. When the rider presses down on the electronic brake levers, the controller cuts power to the motor. Additionally, others have a regenerative function where they route power back to the battery from the motor when the regen brake is activated. They convert the kinetic energy harnessed from braking to electric energy, which is then channelled back from the motor to the battery for an even prolonged range. Almost all controllers in modern scooters have this feature.

s06p, s-ku63, torque, simulation, motor

E-scooter controllers are categorized based on motor type, functionality, and rating in terms of current and voltage. Powerful scooters, especially those with dual electric motors, usually have two controllers with higher max current and voltage ratings but one throttle input.

Where is an Electric Scooter Controller Housed?

In e-scooters, the controller is usually placed in a metallic rectangular sealed protective box and mounted deep inside the frame, the electric scooter deck or stem. The metallic enclosure comes in handy to facilitate heat conduction, allowing the components of the controller to function optimally. E-scooter controllers can easily be noticed owing to the numerous wires and fuses of different colours emanating from the metallic enclosure.

How Do E-Scooter Controllers Work?

Electric scooter controller components can be categorized into two broad groups, i.e. main chips (microcontrollers) and peripheral components, i.e. MOSFET, sensors, resistors, etc. They also encompass various electronic circuits, including power circuits, AD circuits, PWM generator circuits, power device driver circuits, over-current under-voltage protection circuits, and signal acquisition and processing circuits, among other components.

The different components work in combination, governed by software integrated into the circuit board. The functioning of the e-scooter controller is wholly dependent on the microcontroller, which acts as its brain. The microcontroller, also called the processor, receives several inputs, including control signals from various e-scooter components/sensors, including brake, throttle, and motor speed. Once it receives a signal, the microcontroller, with the help of the software (firmware), analyzes the signal and determines the suitable output signal and its timing.

For instance, when you twist or press the throttle, the acceleration sensors signal the controller requesting it to increase the motor revolutions. The microcontroller picks up this signal, interprets it, and stimulates the motor to revolve at a particular speed based on the signal. To do this, the microcontroller relays the signal to a setup of field-effect transistors (FETs), which function chiefly to drive the motor. The FETs, which are the final recipient of the acceleration signal from the throttle, act as valves to regulate the flow of power from the battery to the motor and ultimately determine the final speed of the scooter.

The FETs are linked to the MOSFET drive circuit on the controller to rotate the motor and control its speed. This circuit rapidly switches the FETs, producing the characteristic electric motor motion. The controller can make the motor spin faster or slower by fluctuating the duty cycle- the instances the FETs are on vs when they are off.

In addition to modulating the duty cycle of the FETs, the microcontroller is also responsible for modulating the timing of power delivery to the motor. E-scooter motors contain electromagnets (poles) that can only be activated by precise power delivery based on the motor’s revs. The controller constitutes a sensor that determines the exact speed of the motor, enabling the microcontroller to fluctuate the frequency of power delivery which in turn activates the electromagnetic poles in the motor.

The controller also supplies voltage to the various external scooter components via the power circuit. The under-voltage circuit prevents the battery from discharging when the voltage is lower than the controller set value. In contrast, the over-current protection circuit limits the functioning of the battery, motor, and controller at a higher current, leading to damage of the e-scooter components.

S06P / S-KU63 torque simulation motor controller

250W DC brushless motor controller X8M06-C

Kunteng motor-controllers S06P versus S-KU63

There are two versions of this controller, the S-KU63 and the S06P. Also, they are marketed as torque simulation controllers, see more about this in the article How do torque simulation motor controllers work? The S-KU63 and the S06P are almost the same:

  • The S-KU63 has an additional 3-speed switch connector and a 5-wire Hall sensor connector. It also works without Hall sensor.
  • The S06P has a 5-wire LCD connector and no Hall sensor connector.

Failing S06P produces loud squealing noise

Sensorless brushless motor controllers, as the S06P, eliminates the need for built-in Hall sensors, which were normally required for commutation. These controllers utilize a technique called Back Electromotive Force (Back EMF) measuring to determine the rotor position and control the motor’s operation.

In the past, I had had good experiences with the KU63 sensorless brushless motor controller. It works very well with my Q85 motor, and I have been using this combination for 10 years without any problems. But this controller is discontinued.

The S06P, has unfortunately proven to be incompatible with my Q85 motor. I have made a video of this issue. The motor exhibited loud squealing noise and stopped working, revealing a malfunctioning back EMF circuit within the S06P controller as the cause:

The back EMF measurement circuitry of the S06P differs from the old KU63, the S06P use a separate board for this.

s06p, s-ku63, torque, simulation, motor

The back EMF electronics of the KU63 work in a different way than that of the S06P: The KU63 has an extra microcontroller feedback connection that controls 6 transistors on the circuit, which the S06P lacks. See the KU63 schematic below.

s06p, s-ku63, torque, simulation, motor

Motor controller S06P improved connection diagram

Unfortunately, BMSbattery provides an incorrect connection diagram with the S06P, here is an improved version. There is a cruise control connection but it is unknown how this works.

S06P square wave current controlled motor controller Motor controller S06P improved connection diagram

Motor controller S06P PCB

I have reengineered the input circuits of the S06P:

Motor controller S06P input circuits

Xiongda 2-speed controller KT36SVPR-XD15D

The Xiongda 2-speed hub motor has to be controlled in two directions, this requires a special motor controller: the KT36SVPR-XD15D.

Xiongda 2 speed controller KT36SVPR XD15D connections

I have found that this controller uses the same Kunteng PCB as the as the S06P: the KTE-6S3-D3c. I think that’s only the software is different in both controllers. Here are the differences:

Controllers KT36SVPR XD15D vs S06P

  • The throttle input is pulled to gnd by uP when the motor is off.
  • The 2-speed motor used to have a 10kOhm temperature sensor that was read by the motor controller. But that has been dropped in new versions.
  • The Xiongda 2-speed motor controller KT36SVPR-XD15D has a ACS711 Hall sensor which measures the current of motor-phase V.

6V light power board

Some controllers are equipped with a 6V power supply for the lighting:

It uses a TPS54160 1.5-A, 60-V, Step-Down DC/DC Converter chip.

Old version KU63 schematic

In 2012, I had reengineered the KU63 motor controller. The circuit may also give insight into other motor controllers. Download the circuit high definition pdf file HERE.

China KU63 BLDC motor controller 36V 250W circuit

Here I am at work in 2012:

Reengineering the China motor controller

KU63 motor controller bottom

KU63 motor controller top, without some capacitors

Old version KU63 motor controller facts

250W DC brushless motor controller X8M06-C

The KU63 motor controller is small and lightweight and well suited for 250W motors.

  • BLDC motor 36V 250W
  • Maximum current 12A
  • Motor HALL sensor or sensorless operation
  • Battery undervoltage detection ~27.7V
  • Overtemperature protection
  • Brake high voltage level and low voltage level input
  • Control LED inside
  • Weight 200g
  • X8M06-C controller IC, TQFP44 housing
  • 6 power MOSFETs 2SK4145, RDS(on) 10mΩ, VDSSmax 60V, IDmax 84A
  • Quiescent current off-state 30uA
  • Consume current with motor at full speed 60mA (excluding motor current)
  • Switching frequency 16.7kHz
  • Throttle voltage 1. 4V

X8M06-C / μPD79F9211

It seems that the microcontroller X8M06-C is the μPD79F9211 from Renesas Technology Corporation. The manufacturer has no datasheet available, but you can download it HERE ,

Here are some interesting application notes for motor control applications with a similar controller, the μPD78F0714:

Current limit

There are two separate motor current limit circuits.The average current limit (CPU-41) reduces the motor voltage by changing the duty cycle. I tested what happens when this circuit is disabled: the maximum motor current will be increased from 14A to 16A. The fast current limit (CPU-31) switches off the commutation transistors too in case of over-current, with a frequency of 16.7kHz.

Disabling PAS / pedal speed control

The behaviour of the KU63 is such that, without throttle, the motor power depends on the pedal speed. I don’t like that, you don’t have direct control over the motor power and sometimes the maximum power is not even reached. With throttle control, which I prefer, don’t connect the PAS sensor and connect the green wire with the red wire at the PAS connector or connect the pin ZL with the 5V pin on the printed circuit board.

Speed limit

The KU63 has a speed limit connector; connect pin XS to GND to enable it. However, this is not a real speed limiter, it is just a simple voltage divider built with R77 and R87. Instead of limiting the speed, the motor power of the whole range from 0 to 25km/h is limited. So, better don’t use the speed limiter. The pedelec legalisation device adds the extra speed limit functionality.

Pedelec legalisation device

The KU63 can be used without pedaling, which is not allowed for pedelecs. Here we need the pedelec legalisation device which can be built into the motor controller, see HERE.

Changing the under voltage limit

Note that the KU63 under voltage limit is only of importance if the battery has no built-in BMS. Normally, Lithium batteries have a built-in BMS which protects the battery from over discharge. We can change the under voltage limit to another value than 27.7V by replacing R50, see for the location at the second image. It doesn’t have to be necessarily a smd resistor. The new value of R50 is:

R50new = R50old UVnew / UVold R55 (UVnew / UVold.1)

  • R50old is the old value of R50, the value varies by product. Measure its value securely.
  • R55 is 1200
  • UVold is the old under voltage limit (27.7). It is preferable to measure the actual under voltage limit yourself.
  • UVnew is the new under voltage limit

Increasing the KU63 motor current

The KU63 maximum current can be increased to at least 20A without overheating; this can be done by tinning the shunt. Please note that this may overload the motor.

Increasing the KU63 voltage

Take the 36V version; the 24V version may be equipped with 35V elcos. For increasing the battery voltage above 36V, take these things into consideration:

  • The maximum voltage of the Mosfets 2SK4145 is 60V.
  • The elcos have a voltage rating of 50V or 63V.
  • The resistor R1, which limits the dissipation of U1, has to be changed.

Without overhauling the whole controller, the maximum battery voltage is 43.2V, which is 12 lithium-ion cells in series. At full charge, the voltage is 12 4.2 = 50.4V. Just R1 has to be changed to (123V-14V-3V)/60mA = 270Ω / 2W.

Changing the power MOSFETs

Here we shall see if it is possible to reduce the losses by changing the MOSFETs.

Conduction losses

The conduction losses are caused by RDS(on). The total conduction loss is: 2 I^2 RDS(on). The MOSFET 2SK4145 inside the KU63, has an RDS(on) of 10mΩ. With a 36V battery, the motor current is 10A at 360W, which causes a loss of just 2W. My experience is that the KU63 barely warms up at full power. When the motor controller may still become hot, it is because of the switching losses.

Switching losses

Switching losses are caused by the simultaneous exposure of voltage and current during the switch transition. Power MOSFETs with a lower on-resistance have larger parasitic capacitances, which cause larger switching losses. So we can’t simply take MOSFETs with a lower RDS(on) to reduce the losses, this may result in increased switching losses that supersede the savings in conduction loss.

Redusing the LM78L05 dissipation

The 5V current consumption is 50mA, which leads to a LM78L05 dissipation of 0.44W, this is close to the allowed maximum. There are known cases where the overheating of the LM78L05 caused failures. By mounting a 100Ω 1206 SMD resistor Rdiss between the 14V and the input of U2, the LM78L05 dissipation will be reduced.

Fail-safe brake lever switch

The original brake switch circuit was not fail-safe. In case of a broken cable, the motor will not be turned off when braking; this is dangerous. To overcome this, modify the KU63:

s06p, s-ku63, torque, simulation, motor

Wire the brake switch to the SH input. During braking the brake signal SH should be 5V. In case of a broken wire, the brake signal will be 5V too; this will turn off the motor. You can use a Hall effect sensor instead of a mechanical switch, see here.

DIY ergonomic space saving e-bike thumb throttle

Instead of a rotating throttle, I use an up-down button instead. It is close to the right handlebar for easy access. The switch is connected to the E-bike cable killer.

Ergonomic space saving ebike thumb throttle

E-bike cable killer

The cable killer is a device that drastically reduces the cabling of an e-bike. All switches, sensors etc. of an ebike are controlled by just 2 wires. See more in this article.

E-bike cable killer inside the KU63 (prototype)

Open-source motor controller

On the website of Casainho in Portugal there also much information about motor controllers and his open-source software project.

MicroWorks 30B4 board

The MicroWorks 30B4 is a popular motor controller board and is used in the open source Unicycle. It contains an STM32F103 processor and can be programmed yourselve.

MicroWorks 30B4 schematic

Casainho firmware for the TongSheng TSDZ2 motor controller (most recent)

The TSDZ2 controller use the same microcontroller STM8 as the KT motor controllers from BMS Battery?

Similar KU series motor controllers

It seems that all KU series motor controllers have almost the same circuit:

  • KU60 350W 6 Mosfets
  • KU63 250W 6 Mosfets
  • KU65 250W 6 Mosfets
  • KU93 450W 9 Mosfets
  • KU123 500W 12 Mosfets
  • KU151 1000W 15 Mosfets

KU123 motor controller

The motor controllers KU123 and KU63 are roughly equal.12 power MOSFETs STP75NF75, RDS(on) 11mΩ, VDSSmax 75V, IDmax 80A

KU123 motor controller CPU

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