Introduction: DESIGN STUDY OF AN ELECTRICAL ASSISTED PEDALING SYSTEM FOR URBAN BIKES

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About: mechatronics engineer, maker

A bicycle will be modeled in SolidWorks to find designs that are easy to assemble. And so carry out the process of studying the materials, cost, manufacturing process and battery consumption. The approach sought to minimize energy consumption losses in the bicycle with its parts, either due to their weight or manufacturing.

Supplies

a bike 26¨

MOTOR BY1020 

dc motor controller

chain

Step 1: Battery Analysis and Controllers

Lead-acid battery. They have been the most used batteries in electric vehicles since their manufacturing years in the 19th century, it is estimated that from their year of manufacture a million batteries have been produced per year and this ease of production has been due to: low cost , abundance of raw material to manufacture them, easy manufacturing, favorable electromechanical characteristics. Their energy density is between 35-50 Wh/kg. Its useful life is between 500-1000 charge-discharge cycles.


Nickel cadmium battery (NiCd). They use cadmium anode, nickel hydroxide cathode, potassium hydroxide as electrolyte. Among the advantages of these batteries is: lower performance at low temperatures compared to lead acid batteries, linear discharge curves, little or no maintenance, as a disadvantage: it has an energy density similar to lead batteries. lead acid and the voltage of each cell is very low 1.2V


Nickel metal hydride battery (NiMH). Nickel-metal hydride technology has electrical characteristics similar to nickel-cadmium technology. The nominal voltage per cell is 1.2V and the charge and discharge curves are quite similar. As in NiCd batteries, the "delta peak" effect is used to mark the end of charge in batteries.


Baterías de iones de litio (LI-ION). La densidad de energía de una batería de la familia del litio es aproximadamente más del doble que en una batería de níquel-Cadmio. Los investigadores aseguran que la batería de litio puede alcanzar un potencial muy superior al actual. 


Lithium Polymer Batteries (LIPo). The lithium polymer battery, also known as lipo, differs from other batteries due to the electrolyte used. The original design dates back to the 1970's using a solid polymer as the electrolyte, this electrolyte was assembled in a plastic container that did not conduct electricity, and that prevented the passage of electrons.

They are widely used in electrical devices where high instantaneous discharge currents are required, such as the motors of a drone or a radio-controlled car.


Lithium-ion batteries with lithium-iron phosphate cathode (LiFePO4). Lithium Iron Phosphate (LiFePO4) has low cost, non-toxicity, high abundance of iron, excellent thermal stability, good safety characteristics. Its main characteristic is its longevity greater than 10 years does not have memory effect, it is not made with toxic products, the battery belongs to the lithium family that better tolerates high temperatures, exceeds 2000 life cycles.

These characteristics make it one of the most used batteries in electric vehicles due to the benefits already mentioned, it is currently being developed for future improvements.


Vbestlife 24v-48v 250w/350w controller

● Material: aluminum alloy.

● Rated working voltage: 36/48 V.

● Rated power: 350W.

● Current: 13A.

● Low voltage protection: 31/42 V.

● Suitable motor phrase angle: 60 / 120 degrees.

● Suitable for: electric bicycle, scooter, etc.

● Approximate measurements: 3.5 x 2.1 x 1.2 inches.

● Approximate weight: 7.20 oz.

These controllers are the most suitable since they have different energy and motor speed control and management systems. Trying to build a controller with these same characteristics would be impractical. Many of these systems come with an integrated throttle control and display. where to view different data on the state of the vehicle.


BY1020 ENGINE

36V 500W reversible DC motor

Rated current: 19A

Rated speed: 2400rpm

Sprocket: 11 tooth for #25 chain type

Step 2: Model and Mechanical Assembly

see model on: https://grabcad.com/library/electric-bike-motor-positioning-1

the frame of this bicycle is desing by Muhammad Hassan Mujtaba on grabcad: Giant ATX 2 MTB:


CALCULATIONS FOR TRANSMISSION

In the following calculations, the technical characteristics necessary for the motor.

Data:

— Rear wheel radius: for a conventional 26´´ wheel

— In Colombia, resolution 160 of February 20, 2017 regulates bicycles

assisted pedaling must not exceed 25km/h and their weight cannot exceed

to 35kg We then start by limiting the maximum speed to 25km/h



Step 3: Conclusions

It is concluded that the most suitable motor for the configuration of the proposed design is the MY1016Z3 due to the fact that it has a gearbox, its speed is 300 rpm, it fits perfectly in the requirements of the transmission.


As for controllers, due to the complexity of controlling the speed of a power motor, the most optimal thing is to choose to buy a controller already designed for these purposes, where it makes efficient use of the current provided by the batteries and controls the speed of the motor. motor at different torque regimes, include protections against overheating and electrical overloads of the motor.


In the controllers studied, the Vbestlife 24v-48v 250w / 350w controller we determined is the most suitable for the proposed design; Since it has different control systems and management of energy and motor speed, trying to build a controller with these same characteristics would be impractical. Many of these systems come with an integrated throttle control and a screen where you can view different data on the status of the vehicle.


As for batteries, for what is analyzed in the collection of information and the approach of a design, the most suitable battery on the market is identified as the Lithium-ion batteries with lithium-iron phosphate cathode (LiFePO4). It has a low cost, it is not toxic, it has excellent thermal stability, good safety characteristics, high energy density, which reduces the total weight of the battery. Its main characteristic is its longevity greater than 10,000 cycles, it does not have a memory effect, it is under development for future improvements. The inconvenience is the accessibility in the market in Latin America. It is also concluded that of the accessible batteries in Colombia, the most suitable is the 36v13ah Bottle Type Li-ion (lithium) Battery due to its relative low weight and versatile design for many frames.