Chapter 1

Motors

E-bike Motors

One of the main components differentiating electric bikes from regular bicycles is the motor. E-bike motor is what gives juice to your bike and moves it forward. There are two types of e-bike motors — mid-drive motors and hub-drive motors.

E-bike mid-drive motor

A mid-drive motor is placed between the pedals at the bottom bracket of the bicycle. It uses the bicycle drivetrain to transfer the motor’s power to the rear wheel and move the bike forward.

Mid-drive motors come in different sizes and weights, but in general, they are rather bulky, making the bike look “fat” from the frame. Because of lower unsprung weight and the ability to use bicycle gears for hill-climbing capabilities, mid-motors are great use for off-road and mountain e-bikes.

closeup of mid-drive motor on an e-bike
Mid-drive motor is placed between the pedals.
Image by N1K081 / CC BY 2.0
Benefits of a mid-drive motor:
  • The motor uses the gearing system and works synergistically with the bike’s gears for higher efficiency, making cycling uphill easy.
  • Has a low and centre weight distribution which makes the bike feel stable.
  • Lower unsprung weight makes them a better use for off-road bikes.

Downsides of a mid-drive motor:
  • Can cause chain and shifters to wear out more quickly.
  • Due to higher complexity and higher power, is more vulnerable to damages thus needs more maintenance than a hub motor.
  • Is often noisier than a hub motor and makes the bike look bulkier.

E-bike hub-drive motor

Hub motor is positioned in the front or rear wheel of the bicycle, placed in the wheel hub. Instead of placing the motor where the pedals are, hub motor is integrated into the wheel making the connection between the motor and the ground direct.

A front hub motor is often easier to install than a rear hub motor. Having a motor in the front hub basically makes the bike all-wheel driven which can help to ride on soft terrains. However, a heavy front hub motor can put too much weight in the front and make the front wheel spin in wet conditions on inclines.

Placing the motor in the rear wheel hub often results with a more balanced weight distribution of the bike. This gives a smoother acceleration and more natural feel to the ride. A rear hub motor is also easier to hide behind the gears, giving the e-bike a stealthy regular bicycle look.

e-bike hub motor
Hub-drive motor is placed in the front or rear wheel of the bicycle.
Benefits of a hub motor:
  • Requires less maintenance than a mid-drive motor.
  • Hub motor doesn’t add any extra stress to chain or shifters because it is not connected to the main pedal drive system.There are also no drivetrain losses because of that.
  • Small hub motors can be basically invisible behind the cassette of the rear hub.
  • Having a motor separate from the pedals gives the bike smoother and quieter operation.

Downsides of a hub motor:
  • Most hub motors have a fixed gear ratio, making it less efficient on steep hills than mid-drive motors.
  • In case of a flat tire, e-bikes with hub motors are more difficult to fix because the motor is placed on the wheel.

All Ampler e-bikes have a 48 V 250 W brushless DC rear hub motor. We’ve placed the motor in the rear wheel to give the bike a natural feel and a stealthy, regular bicycle look.

Chapter 2

Batteries

E-bike Batteries

E-bike batteries are one of the most crucial components on the electric bicycle. Without the battery, you wouldn’t be able to enjoy the electric motor on your bike. In general, there are two main types of e-bike batteries — lead-acid and lithium batteries.

Sealed Lead-Acid battery (SLA)

SLAs are the oldest type of rechargeable batteries. They are the least commonly used batteries on an e-bike. SLAs are very heavy — they weigh three times as much as lithium batteries. They’re also large, making it more difficult to place them on an e-bike. SLAs only last for half as long as nickel or lithium batteries and thus are not useful for commuter e-bikes.

Lithium-phosphate (LiFePO4)

Lithium-phosphate batteries are one of the safest and most reliable moderns battery types. They are commonly used for energy storage systems where maximum lifetime is important. Due to higher cost and lower energy density they are not so popular for electric vehicles.

Lithium-ion battery (Li-ion)

Modern Li-ion batteries offer very good cycle life, are safe in a controlled environment and have a great power-to-weight ratio. That is why Li-ion batteries are most commonly used batteries for e-bikes and electric cars. In fact, Tesla Model S and Ampler bike batteries are assembled from very similar Li-ion cells.

Li-ion batteries have very high energy density and their self-discharge rate is much lower than many other battery types. They do not require any maintenance and they are free from the “memory effect” that goes with lead-acid batteries.

Li-ion battery packs are usually monitored by a battery management system (BMS) that takes care of ensuring long battery life, balancing voltage between different Li-ion cells and protecting the battery from over-charging, over-discharging and over-temperature.

All Ampler e-bikes have a 48 V 336 Wh LG Li-ion battery with built-in battery management system hidden inside the downtube. It takes 2.5 hours for a full charge which will give on average 70 km of electric assist range.

Chapter 3

Electric Assist Modes

E-Bikes vs Pedelecs

E-bike motors can be activated in two ways — with a throttle or by pedalling. In this chapter, we'll look at their differences.

Throttle-activated e-bike

A throttle mode e-bike works similarly to motorcycles and scooters — it has a little throttle mounted on the handlebar. Think of the throttle as a connector between you and the bicycle electronics. When you activate the throttle, it drives power and moves the bike forward, without you needing to pedal.

There are three types of throttles: half grip twist, thumb, and push button. They all get the same work done; the only difference is the way you engage with it (twist or push).

The motor is activated by pushing the throttle on the handlebar.
Image by Stanistani / CC BY 2.0
Benefits of throttle mode:
  • The throttle makes it easier to get the bike moving from a standstill.
  • You can cruise along without the need to pedal.

Downsides of throttle mode:
  • More powerful e-bikes with throttle are legally classified as mopeds or motorcycles, thus needing a licence plate, compulsory insurance and a rider wearing a helmet.
  • E-bikes with throttle-only mode are not allowed in Europe.

Pedal-assisted e-bike

A pedal assisted bicycle (pedelec) can be moved forward only when pedalling. The bicycle has a sensor mounted on the bottom bracket or pedal crank arm that can tell whether the pedals are turning or not, and activate the motor accordingly. Some pedal assisted e-bikes have a sensor measuring how hard you pedal.

Cadence sensor measures if the rider is pedalling. It works like a simple ON/OFF switch — it turns the motor on when you start pedalling and turns it off when the pedalling is stopped. The rider has to control the boost level and speed by manually adjusting the electric assist mode. The cadence sensor is cheaper compared to torque sensors, but the pedal assistance is often counterintuitive, bulky and laggy.

Torque sensor measures how hard the rider is pedalling — the harder you pedal, the more power it gives to the motor. Torque sensor amplifies your every input in real time, making you feel like a superhuman. Torque sensors give a lot more natural feeling to the ride than cadence sensors, however, they also cost more.

The motor is activated by pedalling as you would do on a regular bicycle.
Benefits of pedal-assist:
  • Pedal-assisted e-bikes work just like regular bicycles, giving a lot more natural feel to riding the bike.
  • Compared to throttle-activated e-bikes, pedelecs are also easier to manage — the rider doesn’t need to hold down the throttle and can instead solely focus on pedalling.
  • Pedal-assisted e-bikes are legal in Europe.

Downsides of pedal-assist:
  • If you want to simply cruise around without pedalling, you’ll be better off with a throttle-activated e-bike.

All Ampler e-bikes are pedal assisted with a torque sensor to make the acceleration smoother and keep the natural feeling of riding a bicycle.

Chapter 4

Controllers & Displays

E-bike Controller & Displays

Controller is like the ‘brain’ of your e-bike that connects all the aspect of the bicycle. Display is like the ‘window’ to your e-bike that lets you adjust the motor settings and check the electronics.

E-bike controller

A controller is the on-board computer that controls all aspects of your e-bike. Its main task is to connect the power, the motor and the sensors, and make sure everything runs smoothly. Inside the controller is a circuit board that manages voltage and amperage input and output, and controls all of the critical functions of your e-bike.

An e-bike controller gets energy from the battery and directs it to the motor according to the user and sensor inputs. It monitors battery voltage, bike speed, motor power, pedalling activity and more.

The controller also controls functions such as:
  • Pedal Assist
  • Motor power
  • Voltage cut off
  • Maximum speed
  • Integrated lights
  • Built-in display (if that exists)

Placed inside the frame, hidden away.
A typical e-bike display showing the assist mode, speed, battery level, time and distance.
Image by TJStamp / CC BY 2.0

E-bike displays

E-bike display works like a control unit and a window to your bike. Normally, display shows the riding speed, the level of assistance that’s been activated, and the range left in the battery. Some displays also show riding time and distance and the percentage of incline and decline passed on the road.

In recent years, many e-bike brands have replaced the display with something we all nowadays have: a smartphone. The e-bike is controlled through a mobile app which is connected with the bike via Bluetooth.

In addition to showing basic information about the bike, a mobile app can also help the rider navigate, track the rides, stay informed about the bike electronic updates, troubleshoot for any problems etc.

All Ampler e-bikes connect with a smartphone application. The app lets the rider control the bike’s electronics, track the rides and navigate with built-in maps, check the speed and power and receive updates about the bike’s electronics.

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