The Motor

Bicycle Motorized Wheels:
Third Generation

CycleBooster’s principal product offering is the bicycle motorized wheels . The product is the result of a long series of product enhancements from extensive (Hanselman DC,2006) permanent-magnet brushless motor (PMBL) engineering R&D in the areas of materials selection, optimal mechanical design and exceptionally sophisticated microprocessor controller design

Front view motorized CycleBooster wheelrear view CycleBooster motorized wheel
Hub Motor Sprocket SideHub Motor Cable Side

PMBL Configuration

The basic design configuration is based on a multi-polled hub motor; the outer 320mm diameter aerodynamic rotating hub component (attached to wheel rim) has a circular series of 57 permanent magnets excited by an inner fixed hub with the pole windings arranged in a 3 phased PWM drive (Atmel, 2006). The 3 phase circuit excites 19 magnets per phase resulting in exceptional torque performance. Directional rotation is determined by phase sequencing order relative to a reference sensor, a phase 1-2-3 sequence determines a clockwise rotation while a 3-2-1 sequence derives counterclockwise rotation. The fixed inner hub’s shaft is bolted to the bicycle frame while the outer hub (wheel rim) is secured to the inner hub by a sealed wheel bearing at each end. A power connector and a control connector protrude from one end of the mounting shaft. The outer hub has predrilled threaded holes to optionally accommodate 140 or 160 mm brake disk. Thin geometry (60mm) at the mounting shaft provides for the installation of an optional 6 speed sprocket.

cyclebooster electric bikes inner wheelcyclebooster electric bike innerwheel
Outer Hub Magnet ArrayInner Hub Poles

The Microprocessor Controller (Microcontroller)

The microcontroller is an integral part of the motor assembly and is attached to the fixed inner hub which also serves as a heat sink for the drive power FET (Field Effect Transistors) in PWM (Pulse Width Modulation) mode, this results in high efficiency control as the drivers operate in switching mode rather than in energy burning linear mode. The motor integrated electronics provide for higher reliability and minimization of external wiring as power is delivered directly to the internal controller, this design feature also has the benefit of protecting the electronics from direct external damage, moisture, contamination and corrosion.

Default programming (acceleration/torque and maximum speed) is provided by the manufacturer in compliance to regional regulations. The microcontroller has provisions for user performance programming through an optional USB interface cable.

Cyclist Controls

The cyclist essentially has 2 active controls, a twist accelerator with cruise control and hand brakes that are coupled to provide input for dynamic braking (also called regeneration or regen). The accelerated speed limit is programmable, while the rate at which the limit is reached is dependent on the battery drive voltage. When braking, the motor acts as a generator and delivers the decelerated energy back to the battery, this action may be used in long downhill glides to recharge and extend battery utility. Indeed, this generating capacity is promoted by an affiliate supplier as an emergency pedal driven power source for wilderness campers; likewise the motor may be used as a windmill power generator.

Performance

The motor is rated to deliver up to 1 KW of power, ultimately power output is limited by the battery voltage, the controller has been designed to support 24, 36 and 48 volt battery modules (Performance Curves, 2010).

The wheels may be rear or front mounted however controllers may be paralleled so that a front and rear motor may be installed on one bicycle.

References

(Hanselman DC,2006) Brushless Permanent Magnet Motor Design, Magna Physics Pub, 2006, http://www.eece.maine.edu/motor/BPMM_Ch4.pdf


(Atmel, 2006) AVR447, 8-bit AVR Microcontroller Application note, 2006, for reference only, http://www.atmel.com/dyn/resources/prod_documents/doc8010.pdf

Batteries

CycleBooster uses lithium-ion batteries -- Manganese or LIFEPO4 Chemistry

Lithium-manganese batteries offer one of the highest ranges in the industry — up to 100 KM. They are the most widely used industry standard chemistry and are known for their long life and low replacement cost.

We offer two sizes of batteries:

LiMn 36V/12AH or 36V/16AH
LiFePo4 36V/12 AH or 48V/10AH

Current Technical specifications:

LiMn:


Lithium ion rechargeable battery, 26650 size, LiPF6 electrolyte, Manganese Spinel structure cathode.
High energy density lithium ion battery cell.

Cell capacity: 3.8V 4AH

Cell diameter: 26.24 ± 0.16 mm (top end), 26.16 ± 0.10 mm (bottom end)

Cell height: 65.05 + 0.10/-0.15 mm

Cell weight: 92g

Cell specifications

Rated charge(4A) Limiting 4.0 A, 120 min and constant 4.2V charge at 23±2°C. Recommended charge Reference 1a

Rated discharge Constant 0.8 A discharge until 2.5V at 23±2°C.

Rated capacity 4.0Ah Minimum of rated discharge capacity after recommended charge.

Nominal voltage 3.8V Mean voltage during rated discharge after rated charge.

Shipping voltage 4.03±0.01V Nominal. Approximate state of charge = 80%.

Internal resistance at shipping 23±1 m? By AC 1 kHz.

End of charge voltage 4.20 ± 0.05V

End of discharge voltage 2.5V Discharge voltage used for determination of rated capacity.

Charging time 120min Rated charge.

Maximum continuous charging current 6.5A

Maximum continuous discharging current 10A

Maximum pulse discharging current 40A

Operating temperature:

Charging: 0 ~ 45°C

Discharging: -20 ~ 60°C

Storage temperature: -20 ~ 60°C



LiFePo4:

BMS and 110V-240Vac 2A Universal Charger Included

Weight: below 5.5Kgs

Max Discharge Current: 35A(12AH)/60A(16AH)

Max Continuous Discharge Current: 20A(12AH)/30A(16AH)

Charging Cycles: >2000 times

Operating temperature- -45C-75C