The Parts of an Electric Motorcycle System

An electric motorcycle consists of several key components (battery, controller, motor) and some auxiliary components (display, throttle). I aim to explain the function of each component to those who have just learned about electric motorcycles.

The Battery Pack

Batteries are the energy source that provides power for electric motorcycles, and their cycle life is getting longer and longer. Nowadays, modern lithium batteries made from top-notch batteries are 8-10 times lighter than last year's lead batteries, and if not abused, they are expected to be used normally for 5-6 years.

Lithium battery packs are composed of many smaller lithium batteries that are connected together to form battery modules. Although lithium batteries come in various shapes and sizes. Compared to other types of lithium such as regular batteries or lithium polymers, these batteries have better safety and reliability records. The number of batteries in a battery and the way they are connected in series and parallel determine the voltage and capacity (ampere hours or Ah) of the final battery pack.

The wiring voltage of most electric motorcycle batteries is 48 volts or 60 volts, but you will also see electric motorcycle battery packs as low as 36 volts or as high as 72 volts. 48-72V is usually the best compromise point, completely unaffected by electric shock, and for inexpensive thin wiring and connectors, the current consumption is sufficiently low. That's why most electric motorcycles use this voltage range.

The Motor

Electric motors convert electrical energy from batteries into mechanical energy to drive electric motorcycles. Electric motors can be used in many parts of motorcycles, but in Singapore, we specifically focus on hub motors because they have higher conversion efficiency and can directly replace ordinary motorcycle wheels with electric ones.

The hub motor is directly driven; Small but moderate in yield, either large or heavy and powerful. The optimal choice of motor largely depends on the application. More demanding applications such as cargo transportation or long-distance steep climbing require larger and heavier motors.

The most important attribute required to understand motor behavior is the motor winding constant (RPM/V), typically represented by the symbol Kv. This will tell you the maximum speed of the motor at a given battery voltage, allowing you to know the maximum speed it can help electric motorcycles achieve.

If you want to have a motor that provides a useful amount of power at any of the speeds in that table, it is crucial to choose a motor winding and battery voltage that is at least 15-20% faster than the running RPM in the table above.

Controller

The motor controller is a component that many people are not familiar with, but it is an important component of any electric motorcycle hardware because you cannot directly connect the brushless motor to the battery pack. The motor controller has two key functions

   1) It converts the DC voltage of the battery pack into three-phase AC power of the motor winding. Without three-phase AC power, the motor cannot rotate, and

   2) It can continuously adjust the motor voltage from 0V to the full battery pack voltage based on the user's throttle signal, pedal sensor, and various current limits.

The latter point is the most important aspect that needs to be understood. The motor controller can reduce the voltage provided to the motor to any value between zero and battery voltage.

The motor controllers contain at least 6 power mosfets, large capacitors, and connectors for throttles, brake cutoffs, and displays. The controller circuitboard is often fit in an extruded aluminum box, either mounted externally on the Electric motorcycleor tucked inside the chassis somewhere.

It's also common to have the motor controller located inside the hub motor or inside the battery mounting cradle.

In these latter options, the controller is hidden from view for cleaner Electric motorcycle with fewer visible components, but it is more challenging to repair or replace a damaged controller when it is integrated this way.

The battery, motor, and controller are the main components of the electric motorcycle system, but there are also many accessories and additional components that make up the entire system.

Throttle

A throttle is the simplest and most familiar method for riders to control the power they receive from the motor. This is done by either pressing a lever or twisting a grip on the handlebar. The throttle grants the rider complete authority over the electric motor's power output, regardless of their pedaling intensity.

Nearly all controllers have a plug specifically designed for the throttle input. Fortunately, the throttle signal is one of the few aspects that has been standardized in the Electric motorcycle industry, despite the various connectors used. Almost all throttles utilize hall sensors and a magnet to detect the throttle position. When the throttle is not engaged, the voltage sits at around 0.8-0.9V and increases to 3.6-4V as the throttle is activated.

The two most prevalent types of throttles can be classified as thumb or lever throttles, which are operated by the thumb pushing a paddle, or twist grip throttles that are controlled by rotating a handgrip. Throttles are generally inexpensive, and although they may feel cheap in terms of quality, they are quite reliable.

Ebrakes

An electronic brake sensor is an optional device used to inform the motor controller when the brake levers are being pressed. There are two reasons why individuals may choose to have an electronic brake sensor on their electric bike. Firstly, it serves as a safety measure by automatically shutting off the motor whenever the brake levers are engaged. Secondly, it enables regenerative braking on hub motor systems that support this feature. This allows for a gradual and consistent braking force, with the energy from braking being used to recharge the battery pack.

Currently, both mechanical and hydraulic brake levers are easily accessible with a built-in electronic brake sensor. Additionally, there are also separate sensors available that can be added to existing brakes to achieve the same functionality.

Display

Would follow suit and adopt a similar approach to ensure compatibility across different systems.Unfortunately, this hasn't been the case. Most manufacturers continue to create displays that are specifically designed for their own motor controllers, making it difficult for users to switch or upgrade their systems without having to purchase a new display as well.At Sinepower, we believe in giving our customers the freedom to choose. That's why our display is designed to work with any motor controller that has the necessary analog signals. This means that if you decide to upgrade your motor controller in the future, you won't have to worry about compatibility issues with your display.We understand the frustration that comes with limited options and compatibility constraints. That's why we're committed to providing a solution that gives you the flexibility and freedom to customize your Electric motorcycle system without any limitations.

Hall Sensors

We mention hall sensors not because they are a separate part of an Electric motorcycle system, but because they are often discussed when troubleshooting and swapping components. Typically, 3 Phase brushless DC motors have three hall sensors that indicate the position of the rotor.Certain basic motor controllers only work when these sensors are present, as they rely solely on the hall pattern to time the current changes in the three phase wires. This can be challenging when the motor is stationary or moving very slowly. On the other hand, some controllers use the hall sensors only for starting and switch to sensorless mode once the motor reaches a certain speed.When combining different brushless motors and motor controllers, it is crucial to determine if your motor has hall sensors or not. This will determine which controllers are compatible and which are not.