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Maxun e-kit / E-bike Bluetooth Watt meter

Published: 05 August 2022
Last updated: 27 November 2023

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What is the Maxun e-kit?

The cable killer is an extension board for motor controllers. It performs a wide range of tasks, making it difficult to categorize it with just one name. Its functionality is most akin to that of the Cycle Analyst V3. It adds the following features to an ebike:

I'm still looking for a suitable motor controller, who can help?

Initially, the e-kit was made for the S06P, but it does not work on a Q85 motor. That's why I'm looking for another motor controller, the requirements are as follows:

  • The controller should work for all sensorless e-bike brushless motors.
  • The e-kit electronics controls the motor controller via the analog throttle signal.
  • The PAS sensor and display are not used.
  • Sinus controller is not necessary

The e-kit itself regulates the power control in increments of 50-100-150W, and so on. Due to stability issues of the motor control loop, it is highly desirable for the motor controller to control the motor current instead of the motor voltage. Note that the so-called torque simulation controllers are not actually current (torque) controlled despite their name.

Maxun e-kit parts

The e-kit consists of these parts:

1 Bluetooth cockpit meters

Watt meter cockpitWatt meter cockpit

2 E-kit main board

Prototype Maxun e-kit main boardPrototype Maxun e-kit main board

The main PCB is located inside the motor controller. 

3 Front PCB

Maxun e-kit front PCBMaxun e-kit front PCB

The front PCB contains the connectors and replaces the motor controllers metal front plate.

4 Back plate

The back plate is made of plastic to let pass the Bluetooth signal and replaces the metal back plate.

For sale

All products will be available on my Tindie shop in 2023 or 2024.

Difference with the Cycle Analyst V3

Note that I also have another product that works together with the Bluetooth Watt cockpit meters: the Yamaha dongle.
With the Cycle Analyst , Grin Technologies in Canada has developed a very nice product. Because I will definitely get questions about that, I will explain here what the difference is between my Bluetooth Watt meter and the Cycle Analyst.

Cycle Analyst V3

The main difference is that the Cycle Analyst can control the speed through a torque sensor on the crankshaft, while my system controls the speed using a thumb throttle switch.

  Cycle Analyst V3 Bluetooth Watt meter dongle Maxun e-kit
Torque sensor input Yes No No
PAS input Yes No Yes
Up-down throttle No No Yes
Electronics / display separated No Yes Yes
Motor power control Yes No Yes
Accurate Coulomb counter No Yes Yes


For my solar bike, the Maxun One, I had special wishes regarding the electronics. To increase the reliability, I wanted to reduce the number of cables and connectors. Also, I also wanted to control the speed with my ergonomic thumb throttle switch. Therefore, I developed the Maxun e-kit which also got extra features such as a 5V power output and the connection to wireless meters. I started this project in 2015 and the e-kit has proven to be extreme reliable.

Cabling reduction

E-bikes often have a multiwire cable coming out from the motor that branches out at the handlebar for the display, throttle, ebrakes, light etc. Because each device uses its own cable, sometimes 10 inner cables are needed and therefore also 10-pin connectors. Due to the required miniaturization and water resistance, special connectors are available for this, for example this one from HiGo:

HiGo 10-pin e-bike connectorHiGo 10-pin e-bike connectorRobust Amass MT30 connectorRobust Amass MT30 connector
This solution isn't bad, but it isn't particularly robust either. If you could reduce the 10 cables to 2, then you could use much thicker cables and the very robust 2 or 3 pin Amass connectors. This is the reason why I developed the smart 2-wire bus.
Thanks to the 2-wire bus, you can use the very robust thick Alpha Wire EcoWire:

  • 16 AWG 26/30 for the power cables
  • 18 AWG 16/30 for the control wires

See here the previous situation with the rat's nest of cables coming out of the motor controller and the new situation with the reduced cabling with the e-kit:

Motor controller wiring messMotor controller wiring messMaxun e-kit wiringMaxun e-kit wiring

Connectors on front plate

All cables can be neatly plugged into the connectors on the front, no separate connectors are needed anymore. The used Amass connectors are very robust and over-dimensioned, I have never had any problems with it. This solution was only possible thanks to the use of the 2-wire bus.

Connectors on front plateConnectors on front plate

Motor power control

With thumb throttle switch, the motor power can be controlled in steps from 0, 50W, 100W, 150W, 200W, 250W and maximum.

Bluetooth Wattmeter

The wireless cockpit meters can measure the motor-power, speed, cadence, voltage and fuel gauge / battery indicator. The meters are controlled wireless by the e-kit but can also be controlled by my Bluetooth Watt meter dongle.

Common Watt meters require that the motor current flows through the meter itself, the disadvantage is that it requires long thick cables to the meter on the handlebar. That is why the electronics is divided into two parts: the measuring part is located inside the motor controller or the Bluetooth Watt meter dongle and the other part is the gauge on the handlebar. All gauges together are powered by just two thin wires for the 5V.

The meter without the holder weighs only 8 grams.

Ergonomic thumb throttle switch

Ergonomic thumb throttle switchErgonomic thumb throttle switch

I prefer to control the motor power independently from my pedal effort, so without the use of a torque sensor. This has some advantages:

  • On bumpy roads it is easier to ride out of the saddle when you don’t have to pedal.
  • In critical situations, steep slopes etc., it's handy to be able to use the motor with both feet on the ground.
  • Constant motor power gives a better predictability of the battery capacity.

To control the motor power as easy as possible, I have developed an ergonomic e-bike thumb throttle switch.
For more information, read this: Which are better Torque Sensors or PAS sensor

5V 3A power output

With the 5V output, we can power the cockpit meters and other devices such as a (Garmin) GPS and LED lamps. Several micro-USB connectors are available for this, these are located at the backside of the cockpit meters. Since the output current is 3A, the e-kit can quickly charge smartphones using the USB Power Delivery protocol. 

Note that often a 6V output voltage is used as it is the standard voltage for bicycle lighting. However, 6V is not suitable for charging other devices such as smartphones. Therefore, a 5V output voltage has been chosen. This can also be used for bicycle LED lighting.

Connection Diagramm

The following diagram shows how the e-bike electric parts are connected to the e-kit.

Maxun e-kit connection diagrammMaxun e-kit connection diagramm

Two current controlled busses (Cucobus) are used, one for the electronics at the bicycle frame and one for the handle bar.

I prefer to use aircraft quality Alpha Wire EcoWire

  • 16 AWG 26/30 for the power cables
  • 18 AWG 16/30 for the control wires

Software updates by USB

Anyone can run perform software updates themselves, all you need is an USB cable and the Arduino IDE software on the PC.
The USB connector is available behind the plastic back plate.