DIY electric bike: controller


How to choose a controller for an e-bike, what controllers are there and what is the difference between them?

Before answering this question, let’s figure out why a controller is needed at all.

Surely, almost every curious representative of the male half of humanity in childhood dealt with motors installed in children’s toys, for example, electric cars or boats.

These motors were

In this case, the windings of the rotor (the rotating part of the electric motor) are connected to the power source in turn through a pair of graphite brushes, thus the rotor is set in rotation.

Electric bicycles use

Firstly, DC motors have a unit that requires maintenance and periodic repairs — these are the very brushes and the collector on which they slide.

Secondly, the efficiency of these motors is lower and the weight is higher. Third, they have a limited range of rotational speeds. Three-phase asynchronous motors are devoid of all these disadvantages.

But the latter requires a controller — a device that ensures the switching of the windings strictly according to a certain algorithm.

Depending on the type of engine (with

Power wires are those that are directly connected to the motor windings. And thin (low-current) wires are power wires and signals from position sensors.

In the photo, the power wires (blue, green and yellow) are hidden in glass-reinforced tubes, and the low-current ones are visible: blue, green and yellow are signals from position sensors, red and black are the power of the sensors, and white is from the temperature sensor, which is hidden under board closer to the windings.

The controller determines the position of the rotor using sensors and switches the battery voltage to the required motor winding.

So in what cases

The fact is that in cases where the engine must start with a significant load on the shaft (in our case, you need to move the bike with the rider), motors with sensors are used.

If there is no load at the start or it is insignificant (for example, ventilation), so-called sensorless motors are used. Although, in some cases, sensorless motors are also installed on low-power electric bicycles.

Accordingly, controllers are available both for motors with sensors and for motors without position sensors.

Now let’s talk about execution, that is

And here we again transfer the emphasis to motors that are installed either in a wheel (instead of a hub) or in a carriage assembly.

In the case of a motor-wheel, that is, a motor spoked into a rim, the controller is a separate unit with its own housing, and is located separately from the motor (with the exception of a few specific solutions).

In the case of a central (carriage) motor, the controller is installed inside the motor housing, which reduces the amount of visible wiring on the e-bike.

There is another important characteristic of the controller that affects the travel distance, or, in other words, the efficiency of using the energy stored in the battery.

I mean

The most common —

That is, the PAS registers the very fact of pedaling, regardless of how quickly the cyclist turns them and how much pressure is applied to them.

Another type is less common —

It is easy to guess that the second option is more efficient in terms of the economy of using the battery charge, since it will prevent the cyclist from idling.

Moreover, there is no need to use the throttle knob, because when the pedal is pressed firmly, the controller will supply maximum power to the engine.

Now let’s take a look at the e-bike controller market. Let’s start with one of the most ordered on Aliexpress

If you believe the characteristics stated on the label, it is designed to work with a voltage of 36 or 48 volts and a maximum current of 30 amperes. Controller dimensions 8 cm x 15 cm.

Consider the wires that come out of it, and figure out what each of them is intended for. In general, the seller has written what is what in the product description, but not everyone will understand these labels.

So, in order:

Motor (blue, green and yellow) — three power wires for connecting the motor. I wrote about them above.

Speed meter — signal wire to the speed measuring sensor. But the speed sensor has two wires! Right. The second wire («ground», or GND) will have to be taken from another connector, for example, from the PAS connector.

PAS — three wires to the pedal assist sensor. Typically the black wire is GND, so it can be used as the second wire for the speed sensor.

Alarm — two connectors for alarm connection.

H-brake and Low-brake — wires for connecting brake sensors. In one case, the sensor (or button) is triggered when the signal wire is closed to ground (GND), in the other, when +5 volts are applied.

Cruising — activation of the cruise control function.

Throttle — three wires for connecting the throttle: «ground» (GND), + 5V and signal, the voltage on which changes depending on the position of the throttle.

Battery and Ignition — two power wires to connect to the battery and one signal wire to turn on the controller. When battery voltage is applied to the signal wire, the controller starts up.

Reverse — two wires, when closed, the motor will rotate in the opposite direction.

Hall sensor — a connector for connecting a motor, or rather, position sensors installed in the motor. I wrote about them above.

3 Speed — Three wires for selecting the maximum speed.

Self learn — two wires, when closed, the self-learning mode of the controller is activated. After the controller has completed the learning procedure, the wire is opened.

By the way, this controller does not imply a display connection,


As a rule, the controller, along with the bundle, is hidden in a bicycle bag suspended from the frame. But, as practice has shown, over time, from vibrations and exposure to a humid environment, oxidation of contacts and disruption of connections occurs.

There is also a use case

This controller has 12 power transistors screwed to the controller case for cooling. That is, it is assumed that the controller will be located in the environment, and ideally, it will be blown by the incoming air flow.

However, in a sealed, sealed enclosure, cooling will be difficult and the controller may fail as the transistors burn out.

To solve this problem, use sealed connectors and an integration cable.

In this photo, the following connectors are located from left to right:

An integration cable is a cable that integrates all the wires going to the steering wheel: for connecting the display, throttle grip and brake sensors.

Connector for connecting a flashlight.

Connector for PAS-sensor connection.

Connector for connecting the motor. It combines three power wires, 5 wires for position sensors and 1 wire for temperature and speed sensors.

The yellow connector is for connecting the battery.

Despite the fact that this controller is less powerful (22 amperes versus 30 amperes in the first case), it costs three times more.

But this

In much the same way as experienced installers choose a professional reliable tool in order to be completely confident in it and work with convenience and pleasure.

In addition to controllers from Aliexpress, there are

For example,

Also, mention should be made of domestic development. Company

The photo shows the new controller (below) in comparison with the Chinese counterpart (above), both are designed for a current of 45 amperes.

Of course, the lower controller will be placed in a case that serves as a radiator, but it is obvious that its dimensions cannot be compared with its Chinese counterpart.

The new development is especially interesting in that the controller will support

And of course, in this article, one cannot fail to mention the controllers installed in the central motors.

Many budding e-bike builders will notice that I didn’t consider high-current controllers.

The fact is that powerful controllers mean powerful batteries, powerful motors and, as a result, very strong (often steel)

Then it will no longer be electric bicycles (weighing up to 25 kg), but electric motorcycles, the weight of which reaches 50 kg or more, and pedaling becomes meaningless.

I am still a supporter of light and compact equipment, and I am of the opinion that an e-bike should remain a bicycle.

Thank you for reading the article to the end!

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