Regenerative Battery For Human Electric Hybrid Bicycle Engineering Essay

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In this report, a proposed project, the human-electric hybrid bicycle, also known as "Pedelec" driven mainly by human pedalling force with additional assistance force from the battery powered electric motor that has a regenerative power feature during declining slopes.


Automobiles have always been essential for people living in cities as a form of transportation to carry out their daily routine. According to the International Organization of Motor Vehicle Manufacturers, a staggering number of 77,609,901 cars and commercial vehicles were produced in the year 2010. A 25.8 percent change compare to the previous year (OICA, 2011). Based on a research report of the Fifth U.S. Climate Action Report, transportation activities contribute thirty-three percent of the world's emission of carbon dioxide in 2007 and nearly up to sixty percent of emission came from the combustion of petroleum from personal transportation (U.S. Climate Action Report, 2010). Consequently, it is without doubt, cars are one of the major causes of global warming due to the emission of green house gasses. Currently, hybrid and electrical vehicles seems to be the preeminent solution to counter the problem that arises from petrol powered automobiles without eliminating its advantages. However, electrical powered vehicles have its own disadvantages as it requires a certain amount of charging time. On the other hand, electric bicycle are making huge waves among town communities because it is less strenuous compare to the standard bicycle, thus, enable users to travel longer distance without using much energy. Amount of time needed for charging still arises in electric bicycles. The Regenerative Battery for Pedelecs on declining terrains is able to solve the problem by enabling the user to automatically charge the bicycle battery during downhill slopes.

Literature Review

Electric bicycle, Hybrid Bicycle and Human-Electric Bicycles or Pedelecs have only recently become a worldwide phenomenon due to the rise in petroleum prices. The technology of these types of bicycles is still relative new and research popularity has merely beginning to rise in the past recent years. Therefore, there is lack of research papers and literature available in the area of hybrid or electric bicycle in scholarly journals or professional organization such as the IEEE. The following literature review evaluates on eleven scholarly journals to elucidate the technology involved in developing electric, Hybrid or Pedelecs bicycles and its performance characteristics.

Among the eleven journals included, a report by Muetze and Tan (2007) gave a detailed and organized report based on the characterization of electric bicycle, both theoretically and experimentally. The report includes as well the requirements of different performances ideal for electric bicycles and obstacles faced to endorse it. Regulations and safety factors for electrics bicycles in countries such as Japan, Europe, China and United States are outlined. Research was done to discover the advantages and disadvantages of technical performances for different part type of the bicycles such as the assist type, motor, motor assembly, motor placement, throttle and battery type. The report also includes a power over speed graph collected from results collected with different parameters such as the influence of weight, influence of the slope and influence of wind. Results gathered from the report is able to provide a guideline for developing an electric bicycle suitable for the market trend and improve the performances of electric bicycles for future developments.

While the assessment on the performance of electric bicycle is essential, energy management too must be given consideration. Morchin (1998) identifies the energy consumed by electric bicycle and emission of green houses gasses can be reduced by two methods. Such aspects can be achieved by optimizing the ratings of the battery and engine while delivering power output by each source under expected driving conditions (Morchin, 1998). In the report, an on-board "energy manager" was mounted on an electric bicycle to track the energy level in the battery and effectively divide loads between the battery and the engine. The Langrange's theorem was used to calculate the energy consumed under affecting parameters of air drag, hill slopes and friction. However, the study done only applies to electric powered bicycles and not for hybrid bicycles or Pedelecs. Research can be done to extend for various types of bicycles and different type of terrains. The term "hybrid" used in the paper is rather misleading because the paper focuses on fully electric bicycle while the term "hybrid bicycle" often refers a bicycle that runs on both petroleum gas and electricity or human pedal force with a battery powered motor.

In a related research on power management in electric assisted bicycle, Brand and Ertugrul (2007) examines and discover that an in-hub direct drive located on the front wheel of the bicycle could give better performance by electric braking and stable manoeuvring. Furthermore, the report conducted experiments on 17 riders from different categories. All riders are evenly divided based on gender, weight, age, regular and irregular cyclist. The report is comprehensive and able to substantiate the effectiveness of the in-hub direct drive. Additionally , the report concentrate on evaluating riding conditions of various type of rider group to determine the optimum power requirement and does no focuses on designing an alternative for electric bicycles. It is noted in the report that aerodynamic streamlining and development of a high efficiency inverter can be a further developed from the report.

Most of the study done about electric bicycles revolves around the battery storage system. Solutions may compromise of electric regeneration (Liu et al., 2008); (Somchaiwong & Ponglangka, 2006), or petroleum-electric bicycle (Nagendran & Senthil, 2010);(Xiong, et al., 2010) . Liu, et al., (2008) designed four regenerative braking strategies by turning mechanical energy into electrical energy to extend the battery life-span. Matlab and Simulink were used to create a model of the electric bike and the four proposed regenerative braking strategies. The four braking control strategies are Most Feedback Power (MFP), Most System Efficiency (MSE), Fixed Torque Control Strategy (FTC) and Fixed Feedback Current Control (FFC) (Liu, et al., 2008). Clear description and illustration were given on all the four purposed strategies. The report illustrates theoretically using computer simulations and there were no prototype build or practical experiment conducted with bicycle users.

Alternatively, Somchaiwong and Ponglangka (2006) proposed a regenerative power control system to solve the increment of cycle speed of motor that are redundant for example, during a downhill path. The research experiments on the relationship between the voltages supplied and motor speed. The result shows that if the cycle motor runs on the specific speed requirement, the motor would in turn generate a specific output voltage.

Another prevalent solution battery problems faced in electric bicycles are petroleum-electric hybrid bicycles. Nagendran and Senthil (2010) proposed a Hybrid Bicycle with Three Speed Transmission System to solve problems faces in current electric bicycles. The purposed idea of the hybrid bicycle runs on both electric and petroleum to recharge the bicycle's battery storage system. An added feature to the purposed idea is a three speed gear for effective control the speed of the motor and IC (Internal Combustion) engine. The bicycle runs like an ordinary electric bicycle on Phase One. When the battery storage system is depleted, the motor would then runs on the internal combustion engine. A Change Over is installed to connect and disconnects the motor from the IC engine or vice-versa. A shaft coupler is used to connect the chain drive while a chain drive is used to obtain balance of the bicycle. The research does not illustrate the practical construction of the three speed transmission system.

In a related topic, Liu, et al., designed a LPG (Liqufied Petroleum Gas) - electric hybrid bicycle that is able to run on fully engine driven, fully electric motor driven or hybrid mode. Due to space limitation in the bicycle a four-stroke spark ignition LPG engine power system is introduced in the research. The gasoline engine was modified into a LPG engine by increasing the compression ratio, enlarging the spark advance angle and increasing the ignition energy. The research also includes the design of the transmission system and control system of the hybrid bicycle. A prototype of the design was developed and several tests were conducted on city traffic conditions.

While most studies focuses on a single bicycle type such as electric bicycle or Pedelecs, Indulal & Nair (2007) incorporates both types of bicycle and the implementation of Fuzzy Logic as a control system. The bicycle runs on three different modes, Manual Mode, Power Mode and Automatic Mode. Manual Mode works like an ordinary where pedalling is required with no extra assistance. Power Mode fully runs on electricity and does not require any paddling while Automatic Mode provides electric assistance on top of manual pedalling. Fuzzy Logic is implemented to provide comfortable riding and sufficient drive assistance under any conditions. After the completion of the design, arrays of inputs were fed to the Fuzzy Logic Controller using Matlab Simulation to study the outputs. Results from the simulation found that the performance of the system over various conditions were acceptable. The research states that the design can be further extended into larger vehicles.

To optimize the potential of battery storage system, Sousa, et al., (2007) developed an electronic converter powered by two type power supplies, the battery and super capacitors. Batteries are the primary storage while capacitors are used to avoid deep discharging of the battery and as a backup storage. In this research, supercapacitors are used instead and can able to serve as a primary storage source. The developed system was built on the electric bicycle and results were gathered. A decision circuit is needed because the design is capable in increasing the autonomy of electric vehicles to avoid high current peak and fast discharges of the batteries. The research open doors for future work such as improving power circuit to increase efficiency and analyse the autonomy by altering the role of the battery and supercapacitor. Coates and Charkey (2002) states that batteries testing on Sealed Nickel-Zinc Batteries are conducted for electric bicycle applications because it provides the same amount of energy with half the weight compare to the standard lead-acid batteries.

Hsu,et al., (2011) poses a solution to provide comfort and safety measure in different types of Pedelecs riding environment while optimizing the performance of the battery. The quality of riding conditions can be improved by overcoming three forces of nature, air drag, friction and hill drag. The key to the solution is the pedalling power and total power of the required power should be constant and sufficient additional power is provided to overcome any of the three forces. The design is also able to solve instability problem in Pedelecs when the motor abruptly occurs by keeping the instantaneous acceleration of the assisted power be kept within the Safety Zone and Comfort Zone. Real environment simulation scenarios were conducted on different road types and pedal force in urban areas. Results confirms the design has better energy utilization compare to existing conventional and delta learning rule based assisted power methods. The report provides room for further research on solving the method to automatically adjust the motor to the different type of physical conditions of the riders.

After the evaluation of all the eleven journals, it can be concluded that most of the journals focuses on solving the problems currently faced by electric bicycle that provide insufficient energy in the battery storage and insufficient power assistance. There are ample room for further development on electric bicycles and Pedelecs because it technology is relatively new. Further research done on this area would benefit societies living in urban area to be used as a form of environmental friendly transportation as opposed to conventional cars and motorcycles.

Problem Statement

Based on previous research done on electric bicycles, most studies concur that the depletion of petroleum and the rise in the emission of greenhouse gasses are the factor that contribute to the advancement of electric bicycles (Brand & Ertugrul, 2007; Hsu, et al., 2011; Indulal & Nair, 2007; Morchin, 1998; Nagendran & Senthil, 2010; Sousa, et al., 2007; Xiong, et al., 2010). In spite of this, there are still plenty of room for further development and enhancement in the area of electrical bicycles. The battery storage system incorporated in electric bicycles provides insufficient energy for long distance travels and does not carry self-charging capabilities (Coates & Charkey, 2002; Nagendran & Senthil, 2010). Electric assisted bicycles or Pedelecs confront problems such as an abrupt driving force when the motor is triggered (Hsu, et al., 2011).

Project Background

The project focuses on improving the overall performance of electric assisted bicycle or Pedelecs. Since there is a demand on electric bicycles, it would be beneficial for society and business organization to enrol the development of Pedelecs. In a report by Time News, most electric bicycles run on lead-acid batteries and are unsuitable for the rising requirements of daily transportation (Ramsy, 2009). Numerous solutions were established by various engineers and organizations to counter these problems. Some researchers focus on the regeneration of electricity from external sources (Somchaiwong & Ponglangka, 2006; Xiong, et al., 2010). While some concentrate on using distinctive forms of power management (Brand & Ertugrul, 2007; Hsu, et al., 2011; Morchin, 1998; Nagendran & Senthil, 2010). For the proposed Regenerative Battery for Pedelecs project, it confronts both of these methods to solve the battery problems that arise from conventional electrical bicycle. In addition to replacing cars to reduce the emission of greenhouse gasses, the regenerative power during a declining gradient reduces the dependency on electricity. The generation of electricity from Independent Power Producers (IPP) indirectly affect the environment. For instance, the construction of Hydroelectric Plant requires large areas particularly in remote areas and substantial quantities of fossil fuels are used to power up machineries (McKinney, et al., 2007). The natural habitat, home to both flora and fauna would be destroyed in the process. The proposed regenerative power is designed to reduce the power consumption in the battery storage while providing rechargeable power supply at the same time. The regenerative power incorporated in the design would be able to solve issues relating to the insufficient power in the battery storage system. It would be able to expand the life cycle of the battery for longer distance travels. Most electric bicycles owners today complain that electric bicycles do not provide sufficient power assistance. The latest Pedelecs today has power-assistance during hill climbing or on irregular surface roads to provide the additional boost without having the rider to exert much force. However, Hsu,et al., (2011) states that there are insufficient power assist to overcome three forces, air drag, friction and hill drag. Air drag and friction does not require much power compare to hill drag. The motor of the power assist provides enough force to overcome hill drag, friction or air drag while the pedalling power by the rider remains constant. This would be enable riders to conserve energy for longer riding.

Most seniors find that conventional bicycles are strenuous and dangerous. Therefore, some seniors would rather stay in the comfort of their homes without getting much exercise and fresh air. Pedalecs would be able to encourage seniors to overcome their fear towards conventional bicycles.

In urban town areas, getting out buying some groceries would sometimes be a hassle especially if the grocery shop is not within walking distance. Most people today would rather drive their car out to buy some fruits and vegetables or to fetch the daily newspaper. It is a very unhealthy habit that began to manifest among the town citizens. Little did they know that getting fresh air by cycling or taking a daily stroll would improve the well-being of the person and reduces health risk such as diabetes and cardiovascular disease. According to a Congressional Report, less than one trip in one hundred percent is by bicycle (Congress, 2002). The report also mentioned that frequent bike trips would also cure the addiction of smokers and alcoholics.

Regenerative braking in electric bicycles is gaining popularity too. The Panasonic Vivi RX 10-S features a braking system that recharges a 10AH Li-ion secondary batter located next to rear wheel of the bicycle (Toto, 2008). Liu, et al., (2008) mentioned that braking control can be used to convert mechanical energy to electric energy by improving battery life-span. Using the same theory, the proposed design is able to make use of hilly areas to generate electricity. Since no energy is needed for bicycle going downhill, the bicycle still moves downwards due to the forces of gravity. For certain cases, with the regenerative power, braking is not required because the regenerator is able to reduce the speed of the overall bicycle while going downhill.


The scope of this research is divided into five stages. The time scope of the project is expected to be completed in 9 months.


At the beginning of the Final Year Project, intensive research on the area of electric bicycles must be done before designing of the project takes place. Research would be an explanatory research in the beginning to obtain an overview on the research area and to discover alternatives to the research objective. Evaluation on other research papers done to identify the new developments in technology and rooms for further studies is noted. Solutions can be developed by acknowledging the problem faced by the society today. Qualitative Research such as surveys and Questionnaires can be conducted to identify the current problem faced for further development. This is important because the success of a product is determined by meeting the demand of society today. Brainstorming sessions are required after the collected data is evaluated to determine the feasibility of the project and to acquire various alternatives to the problem. This stage is expected to complete within a month.


The designing process takes place after the evaluation of the collected data is finalised. A basic concept should be achieved at this stage. All the knowledge on mechanics, electronics and programming is required to design the proposed idea. Computer simulations are to be use to design and test the feasibility of the idea. Autodesk Inventor can be used to construct the framework and provide a visual overview of the bicycle. Matlab and Labview can be used in the programming development of the regenerative power system. Computer simulations are used before the construction of the bicycle to virtually simulating the design while reducing unnecessary expenditure. This stage is expected to complete in 2 months.


The implementation stage involves building the prototype based on the finalized design. A conventional bicycle is required as the main structure of the design. Motor, Lithium Ion Battery and Transmission System is needed to modify the bicycle into an electrical-assisted bicycle. Torque Sensors, Slope Sensors or Tilt Sensors are installed to sense when the motor is needed. The Slope or Tilt Sensors can be replaced by Apple Application known as Gyroscope for an extra appealing feature. Additional hardware such as a state-of-charge indicator, power tab hub and throttle switch can be added later on. This stage is expected to complete in 3 months.


The testing phase involves the practical assessment on the now fully built bicycle. Various tests would be performed to determine the performance of the entire system. Two types of testing can be conducted, laboratory testing and field testing. Laboratory testing involves a set of variables such as power, efficiency, cycle speed, life-span of the rechargeable battery and the motor. For field testing, a laptop with a PCMIA card is incorporated to the system to acquire the data. The testing would involve around twenty volunteers from different age group, gender, weight and physical fitness level. All volunteers have to go through a predetermine path with different type of terrain in an urban area. The laptop is used to record data such as pedalling torque, bicycle speed and applied power. The data collected is to be used to evaluate the performance of the system. A set of feedback forms could be given out at the end of the testing to gauge the satisfactory level of each volunteer towards the system. This stage is expected to complete in 2 months.


Report writing is to be conducted at the end of all the four stages. The scope and design process in building the system are to be complied. The data collected are tabulated in graph and figures to illustrate the outcomes. This stage is expected to complete within month.


There is some limitation that would be encountered in the process of implementing the system. Budget constrain would be a factor due to the costly hardware needed to construct the bicycle. A full-size prototype is more appropriate because a smaller-scale prototype would not be serving its purpose. In a newspaper report by The Star, due to safety issues, electric bicycles may be taken off the road if the Cabinet accepts a recommendation from the Transport Ministry (Kong, 2011). If the amendment of banning electric bicycle is implemented throughout the country; it may also affect the field-testing of the system.

Research Objectives

This study embarks on the following objectives:

To produce an environmental friendly transportation as an alternative to petrol consumption cars

To solve instability issues involving the abrupt acceleration when the motor is turned on

To provide an alternative regenerative power on declining slopes to lengthen the life-span of the battery storage system

To improve the overall performance to Pedelecs that are available in the market today

To design a form of transportation for suitable in dense populated urban areas

Research Question

What are the current impact on the environment and ways to solve the problem?

What are the current issues faced by electric bicycle?

What addition or alternative regenerative power can be installed to conventional electric bicycles?

What can be done to appeal to the market segment to buy the product?

How to solve issues involving unhealthy habits of the society by relying on cars for short distance travels?

Significance of the Project

The proposed regenerative bicycle would be able to serve as a stepping stone for further development on electric assisted bicycles. Studies by other researches can be done by referring of the design system used and the data collected. Limitations and problems identified can be solved by future research. The proposed design hopes to significantly reduce the emission of greenhouses gasses emitted by petrol driven cars. If the design meets the demands of the society, manufactures would start producing more electrical assisted-bicycle which in return, reduces the market price of the system to reach out to all segments of the society.

Expected Results

The expected outcome of this project is to successfully develop a working actual size electrical assist bicycle prototype capable of converting mechanical energy to electrical energy. From the project, novel theories can be established that would indirectly benefit other areas of sciences. Furthermore, the theories presented would lead to implementation for future potential applications. The tabulations of data collected from the project is to also encourage potential researchers especially budget constrain researchers to engage in the area of electric powered vehicles. A stable handling electrical assisted bicycle is expected to be built to provide safe and comfortable riding experience. In return, physically fit or unphysical fit riders would be able to fill the joy of riding a bicycle for travelling or recreational use. The design and technology incorporated in the project is expected to appeal to the society and provide as an alternative to cars and motorcycles. This would directly reduce carbon footprint and slower the process of global warming.