HYBRID ELECTRIC VEHICLE POWERED BY SUPERCAPACITOR AND BATTERY
Abstract- The aim of this paper is to design and develop a hybrid supercapacitor electric vehicle. The model developed consists of two sources one is constituted by batteries, and the other by supercapacitor. The source is connected to hub motor with the first quadrant of operation. The major problem of present electric vehicle is the failure of battery and high charging time so, the proposed model of the electric vehicle starts the hub motor with supercapacitor bank as the charging and discharging cycles are very high compared to other sources i.e. 1 million cycles . The other problem is the high charging time which is rectified by using supercapacitor, as there is very low ESR (equivalent series resistance) compared to other storage sources. The main aim of going hybrid is because the discharging time in supercapacitor is very less due to which there will be a limitation in distance covered. The charging of the electric vehicle is by normal AC source and the second method is the solar panel which charges the supercapacitor while the vehicle is in the stationary position. The main weakness of the system is the thermal energy output from supercapacitor which reduces the final result of the electric vehicle.
Keywords—battery, supercapacitor, hub motor, motor drivers.
I. Introduction
The present world is taking a shift to the electric vehicle due to the recent variation of the global climatic condition by using IC engines. The report from the Republic of China tells that by using an electric vehicle also produces pollution due to the replacement of the batteries and the failure of
batteries. The battery has charge and discharge of a few hundreds of cycles, which can be replaced by supercapacitor which has millions of cycles compared to a battery. for example, the car tech giant Tesla uses 18650 Li-ion battery which has few thousand of cycles. The main disadvantage of the supercapacitor is the energy density which is 30wh/kg. A hybrid source will solve the existing problems.
II. PRESENT E-BIKE TECHNOLOGIES
The present E-bikes developed or commercially available in the market uses mainly three types of sources i.e. VRLA (valve regulated lead acid) battery, 18650 Li-ion battery (developed by Panasonic) and 21700 Li-ion battery (developed by Tesla Motors). Present battery technology requires high charging time whereas IC engine requires time to fill the tank, this difference makes the electric vehicle move backward but other factors like efficiency and running cost give superior result the IC engine. To eliminate the main problem researches are developing supercapacitor to increase energy density and to reduces the charging time. The current situation of supercapacitor is very basic, it has very less energy density compared to battery. This paper focus mainly on increasing the distance covered by E-bike and to overcome problems in battery and supercapacitor by combining them. During literature survey many supercapacitor E-bikes are available.
A. Design and Development of a Prototype Super-Capacitor Powered Electric Bicycle at IEEE 2014
The author in the above paper used the only supercapacitor to drive the E-bike this gave only 1.1 km of a ride. They have used a module supercapacitor of 72 KJ energy. It has a major problem as the range is very less, which can be overcome by this paper. This paper combines battery and supercapacitor which gives range higher then survey paper.
B. Design Approach for Electric Bikes Using Battery and Super Capacitor for Performance Improvement at IEEE 2013
The author in the above paper used both supercapacitor and battery to drive the E-bike. They have connected supercapacitor and battery parallel to each other, then the motor is connected to the source. They have used a microprocessor which is programmed in such a way that the starting operation of the bike is given by supercapacitor and then while running battery will supply the motor. It has some drawbacks of charging time which can be overcome by this paper. In this paper, the bike can be run by supercapacitor only so the charging time is 3 minutes which is way less than the survey paper.
III. DEMERITS IN PRESENT E-BIKE
A. Long charging time
Batteries used in present E-bikes are VRLA (valve regulated lead acid) and Li-ion which take 7 to 9 hr of time for a full charge.
B. Battery issues
1. The present battery technologies used in the market i.e. valve regulated lead acid and Li-ion have a charging cycle of few thousand of cycles, after the lifetime of batteries they have to be changed for every two years.
2. Batteries take half the amount of weight and space in the electric vehicle.
IV. PROPOSED E-BIKE SOLUTION
Based on the demerits, the proposed model of the E- bike is made. It consist of a battery of 24V, 7.2AH and supercapacitor 24V,187.5F is series with the DC motor of 24V, 250W. A bidirectional relay controller is connected between battery and supercapacitor having a functionality of over current, over voltage, under current, under voltage, reverse current protection. The motor is controlled by PWM controller with a resistive throttle. The throttle uses variable resistance for acceleration of the bike. An individual charging method is given to the battery and supercapacitor. A provision of solar panel is given to the supercapacitor while the bike is in a stationary position.
A. chassis design
A cycle of 26 inch wheel is modified to E-bike as the rare wheel of the cycle is connected by PMDC (Permanent magnet DC motor) with a freewheel which is driven by chain drive. The other side of the wheel is the main freewheel which is driven by pedal of the cycle. The handle of the cycle has electric brakes and throttle which acts as an accelerator. The main reason for the mounting motor rare side is to give even weight distribution of the rider and the battery. The bike chassis can handle a weight of 120 KG but is regulated to 100 KG.
B. Transmission and Power
Transmission is used to transmit the power from the source to the drive wheels in order to provide an easy power transmission, starting capacity and to improve drive comfort, we go for chain and freewheel transmission.
1. Self-weight analysis
Bike self weight= 25KG.
Riders weight = 80KG
total weight = 105KG or 1050N
2. Torque
It is an important parameter which gives the exact power value the motor should provide to move the bike.
· The gross vehicle mass GVM= 105KG= 1050N
· Radius of the wheel RW= 0.33m
· maximum inclination angle (α)=17degree
Step 1: Determination of Rolling Resistance (RR)
RR = GVW x Crr
Where Crr - Surface Friction (0.01)
RR = 1050 N x 0.01 = 10.5N
Step 2: Determination of Grade Resistance (GR)
GR = GVW x sin (α)
GR = 1050 N x sin (17°) = 306.99 N
Step 3: Determination of Total Tractive Effort (TTE)
TTE = RR + GR
TTE = 10.5+306.99
TTE = 317.49
Step 4: Determination of Wheel Motor Torque (Tw)
Tw = TTE x Rw
Tw = (317.49) N x 0.33
Tw = 1057.24 N-m
C. Energy storage system
The bike consists of battery and supercapacitor in series.
1. Battery
Two 12V, 7.2AH batteries are connected in series to make 24V, 7.2AH
Battery runtime:
Total peak voltage=24V
Current capacity=7.2Ah
Total battery power capacity=peak voltage*capacity=24*7.2=172.8wh
On continuous load battery runtime can be estimated as = usable power/rated power of motor =172.8/250=0.69hr
2. Supercapacitor
The supercapacitor does not have a traditional dielectric material but has a double layer dielectric medium. 24 supercapacitor of 500F and 3V are connected in a combination which gives 24V and 187.5F capacity.
Energy= (1/2)cv^ 2
E= (1/2)(187.5)(24)(24)
E= 54000J= 54KJ
supercapacitor runtime:
power = energy/time
time= 54000J/250W= 216 seconds.
D. Motor
PMDC(permanent magnet DC) motor of 24V, 250W is used to drive the bike. The motor produces a speed of 300 rpm, 5Nm of torque with an efficiency of 85%.
1. Calculations of rated current (Ir):
Ir = rated power of the motor (pr) / rated voltage of motor (V)
From the specification, let Pr=250w, V=24v
Ir=250/24=10.4A
2. Calculations for the value of Km:
We know that, 
=V/Km
(in rad/s)
=V/Km (in rad/s)
2
N=rated speed of motor/rated input voltage of motor
N=300/24(rpm/v);N=12.5rpm/v KmФ=24/2πx12.5 =18.3wb
3. Calculating the max torque using the value km
Tmax=kmФ x peak current = 1.83x 10.41 = 19.03 Nm
V. Real Model of the prototype
Overall Hardware Unit
source kit
Motor setup
Charging Setup
VI. REFERENCES
1) Manoj. E, Dino Isa, Roselina Arelhi, “Supercapacitor / Battery hybrid Powered Electric Bicycle via a Smart Boost Converter”, Department of Electrical & Electronic Engineering, University of Nottingham Malaysia, World Electric Vehicle Journal , Vol. 4 - ISSN 2032-6653 - © 2010
2) Nikhil Hatwar, Anurag Bisen, Haren Dodke, Akshay Junghare,” Design Approach for Electric Bikes Using Battery and Super Capacitor For Performance Improvement”, Electrical Engineering Department G. H. Raisoni College of Engineering, Nagpur, India, 2013 IEEE
3) Keagan Malan , Michael Coutlakis , James Braid,” Design and Development of a Prototype Super-Capacitor Powered Electric Bicycle” ,School of Electrical and Information Engineering, University of the Witwatersrand, Johannesburg Private Bag 3, Wits, 2050, Johannesburg, South Africa,2014 IEEE
4) Meutze and Y. Tan, “Electric bicycles - a performance evaluation,” IEEE Industry Applications Magazine, vol. 13, no. 4, pp. 12–21, Aug. 2007.
5) Bhaskar Krishnamachari, “Bidirectional buck-boost converter with variable output voltage”, Department of Electrical Engineering, The Cooper Union, New York, NY 10003,
6) Juan W. Dixon, Micah Ortúzar and Eduardo Wiechmann, “Regenerative Braking for an Electric Vehicle Using Ultra capacitors and a Buck-Boost Converter”, Department of Electrical
Engineering, Catholic University of Chile, Casilla 306, Santiago,Chile.
