CHAPTER- 6

DESIGN &

MODIFICATION OF ELECTRIC

VEHICLE

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DESIGN & MODIFICATION OF ELECTRIC VEHICLE

6.1 Introduction

Besides having so many features the electric vehicles are not a very

common name especially in India market. The basic reason why the

customers are reluctant to buy the electric vehicle is its efficiency. Such

vehicles are not suitable for long journey, as it is required to recharge after

covering certain distance. Whereas with gasoline based vehicle one time

fill will last for a long distance depending upon the mileage of the vehicle.

Also the fuelling does not take long time but to charge a electric vehicle it

takes 6-8 hrs.

Increasing its efficiency can only increase the popularity of the electric

vehicle. If the vehicle will run for a long distance after one time charge,

people will surely come up to buy the vehicle.

The very basic idea by which efficiency can be improved is by charging the

battery of the vehicle during running condition. Now the question arises

how a battery can be charged when the vehicle is running since it needs

continuous A.C current supply to get charged. Well the simple answer to

this question is a decades old theory ALTERNATOR.

ALTERNATOR is a device similar to the generator its basic function is to

generate electricity Some theory below will clear the concept of electricity

generation through alternator

6.2 Electricity And Magnets

When you put electncity (current) down a wire, the wire will have a

magnetic field around it. Conversely, if you move a wire through a

magnetic field, a small current (electricity) is created in the wire. The more

wires you use and the greater the strength of the magnetic field, the

greater the effect becomes. These two inverse principles are the basis for

electric motors, generators, alternators, and even things like the solenoid

inside of a relay. If you have one item (movement or electricity), you can

convert it into the other. Also tied in here is the fact that magnets repel and

attract each other- that's pat of how you make an electric motor move. You

can use more turns of wire (windings) to generate a stronger effect.

What about voltage vs. current? Well, current is a measure of how much

stuff is flowing down a wire - kind of like the number of gallons of water that

are flowing down a pipe every second. Voltage is a measure of pressure -

like how many pounds per square inch (PSI) of air are in your tires. They

measure different things, but they can be confusing since you can't "see"

electricity.

What about AC vs. DC? These stand for Alternating Current and Direct

Current. AC is the stuff used in your house. DC is the stuff used in your car

and what you get out a battery. The difference is that in DC current always

flows in the same direction - from positive to negative (or, if you're a real

phys1cs geek. from negative to positive) - while AC alternates the flow of

current between the two d1rect1ons at some rate. This rate is expressed as

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cycles per second, or Hz (pronounced "hurtz"). In the USA, the electricity in

your house is changing directions at 60Hz- 60 times a second.

The final tid-bit of information is that when you spin wires and magnets

near each other, you create AC in the wire. This is because the wire and

magnets are continuously moving closer to and farther away from each

other in a repeated cycle. As they move closer together, the current moves

one way. As they are farther apart, the current goes the other way. If

you've ever seen the typical "sine wave" graph of AC power, that exactly

what I'm talking about here. This is important because you need some way

to make that AC into DC to use it in your car. The process of charging AC

into DC is called rectification. How you choose to do that is the key design

difference between an alternator and a generator.

6.3 Alternator

The more modern and more capable alternator is explained here. Every

modern vehicle uses an alternator - and for good reasons. It is more

complicated than a generator, but that added complexity brings a few very

good features that you will most certainly want on your vehicle - mainly the

fact that it will charge the battery at idle and can support the higher

amperages needed to run all of the electrical equipment on a modern

vehicle Alternators tend to be more reliable than a generator and have

fewer "hard to diagnose" problems as the system ages - particularly the

1nternally regulated models The rnternally regulated models are also very

I.' X

easy to service if something goes wrong - there is only one part to fail (the

alternator itself) and replacing it 1s a simple 30 minute job. This all adds up

to the performance and reliability that is expected in a modern vehicle.

The key different between an alternator and a generator is what spins and

what is fixed. On a generator, windings of wire (the armature) spin inside a

fixed magnetic field. On an alternator, a magnetic field is spun inside of

windings of wire called a stator to generate the electricity. This allows the

wires to be directly and easily connected to their outputs without the need

for sliding contacts to carry the relatively high output current. The magnetic

field is still generated via electro magnets mounted on a rotor, and the

relatively small field current that powers them is supplied to the rotor by two

small brushes that each ride on a separate and continuous slip rings.

These smooth slip rings (unlike the comparatively rough contacts on a

commutator in a generator) and the fact that the relatively heavy windings

are fixed instead of rotating allows the alternator to be spun to much higher

speeds. This allows it to reach it's maximum output sooner and to be spun

fast enough at engine idle speeds to produce enough electricity to power

most (if not all) of the needs of the car without relying on the battery.

There are typically three separate windings of wire in the stator that are all

set to so that the AC current that is generated is slightly out of phase in

each one. The peaks and valleys of the rising and falling current do not

happen at the same time. rather they are staggered a bit. This increases

and smoothes the electncal output of the alternator much the same way

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that a 8 cylinder car runs more smoothly than a 4 cylinder one does - there

are more power pulses happening in each revolution allowing more total

power and better smoothness

The process of rectifying the AC current into DC current is handled inside

the alternator by something more complex than a commutator - diodes. A

diode is a "solid state" device that allows current to flow in one direction

only without any moving parts. It relies on the different electrical properties

of the materials it is made of to act as a one-way valve for current. By

arranging diodes so that current from each of the three stator wires is only

allowed to pass in one direction, and by connecting the three outputs

together, you get a very smooth and stable DC output without any moving

parts. (This arrangement is typically manufactured as a single part and is

referred to as the diode pack or diode trio.) This lack of moving parts

makes the alternator not only very reliable - but also comparatively

inexpensive to build and repair.

Alternators do not need to be polarized after installation. You mount them

to the engine, plug them in, and go. This is an advantage for not only

manufacturing the car but for servicing it as well.

On externally regulated models, there are typically four connections on the

alternator - the large output terminal (BAT), the ground terminal (GRD)

which may be "implied" though the metal mountings of the alternator. the

f1eld connection (F). and terminal #2 on the regulator 1s a separate

connect1on to one of the three poles on the stator (R) Unlike on a

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generator, the BAT terminal is directly connected to the battery and the rest

of the cars wiring system, while only the F, R, and GRD connections will

connect to the regulator. Also , terminal #3 on the regulator (if present) is

connected to the main junction block for the wiring system and serves as a

"remote volt~ge sensing" wire. Terminal #4 on the regulator will be

connected via small wires to the charge indicator light on the dashboard of

the car and the charge resistance wire. The regulator itself can be a

mechanical or solid-state device. A typical externally regulated alternator-

wiring diagram is shown in fig 6.1.

OILCOTRON

Fig 6.1 Externally regulated alternator-wiring diagram

On internally regulated models, there are also four connections on the

alternator, but there is no separate regulator in the system - it is inside the

alternator and constructed of solid-state components. The connections

here are the large output terminal (BAT), the ground terminal (GRD), which

may be "implied" though the metal mountings of the alternator, and two

connections typically labeled simply 1 and 2. Terminal #1 on an internally

regulated alternator is the same as terminal #4 on the regulator of an

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externally regulated system - it connects to a small wire that is goes to the

charge indicator light on the dashboard of the car and the charge

resistance wire. Terminal #2 on an internally regulated alternator matches

terminal #3 on an external regulator - it is connected to the main junction

block for the wiring system and servers as a "remote voltage sensing wire".

If you are comparing to the externally regulated wiring, then you will note

that the F and 2/R wiring connections are done inside the alternator. A

typical internally regulated alternator wiring diagram shown in fig 6.2

-::::----, ... - .......... .. -···1· ll.f 1'1\'S~~

I. ~ I

" lc• '-,._, ---iliS---. i ,,..,,(~101' 1 ""'~ 1

L4:::.::=$.==:::. =~:=:=:JI .. .,.,. "'"~( t•

tJ(~ =~=~·) t"Ch •~r¢11

Fig 6.2 Internally regulated alternator wiring diagram

6.4 Regulator

What exactly does that little black box on your inner fender do? What's the

difference between internally and externally regulated alternators? The

regulator does just what it's name implies - it regulates the output of the

generator or alternator to the proper voltage and current by controlling the

field current that 1s supplied

For all generators and externally regulated alternators, the regulator is a

small device mounted somewhere on the firewall or the inner fender of the

car. It is connected with relatively long wires to the generator or alternator.

It is usually a mechanical device that works by rapidly opening and closing

the contacts of several relays to create the correct "average" voltage and to

limit the current supplied to the correct amount These mechanical

regulators need periodic adjustments and can be somewhat noisy in

operation. They also have moving parts that will fail after a period of time.

Some later-model and aftermarket replacement regulators are solid-state

devices that are quieter and longer lasting even though they look pretty

much the same externally as a mechanical unit.

For internally regulated alternators, the regulator is a solid-state device (no

moving parts) that is mounted inside the alternator casing. These units will

never need replacement separately from the alternator and will last for

many, many years giving trouble-free service. There are no separate wires

to run between the two units, and there are only a few simple connections

to make at the alternator itself.

6.5 Remote Voltage Sensing

Both regulator styles can have what 1s known as a "remote voltage

sens1ng" feature on them - many thanks to the explanations on the MAD

Enterpnses site for finally making this clear enough to me so I could

explain 1t here They have deta1ls on the remote sensing feature, 1-wire vs.

16.1

3-wire alternators, and a great description of a typical muscle car-era

Chevy charging system. The details are interspersed throughout those

documents, but together they provide very valuable insight into how the

typical alternator-based charging system works, and how to modify your

charging system to work correctly using an alternator. All internally

regulated systems come with the remote voltage sensing feature, but not

all externally regulated systems do. Basically, the remote sensing wire

should be connected to the main junction point for the entire electrical

system. This is because the voltage at the place this wire is connected to

will be maintained at the proper level. If this connection is at the alternator

or regulator, then that's where the maximum voltage will be with lower

voltage out in the rest of the electrical system. If you connect this wire to

the main junction point, then the main junction point will have the proper

voltage. The difference that results from this can be very noticeable,

especially in cars with the battery mounted somewhere besides the engine

compartment A 1 V drop is common between the alternator output and the

main junction point in many cars, so if you have 14V at the alternator and

only 13V at the junction point, you may not be doing much better than 12V

by the lime you get to the actual devices that need to use that voltage_ In

th1s theoretical 1V drop scenano, by connecting the remote sensing wire to

the ma1n junction po1nt. you will have 15V at the alternator (yes, 15V - it's

OK and des1red here). 14V at the junction point, and then 13V at the

accessones

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6.6 Dashboard Indicator Light

If you have an alternator and are using the factory style indicator light on

your dashboard, it is a pretty helpful thing. It helps kick-start the alternator

into working at idle speeds when you first start the car, and it tells you if the

alternator is p~tting out less voltage than the battery has in it, indicating a

problem. The light is connected on one side to the field current system

inside the alternator and to a switched ignition power source on the other

side. When you turn the key on but have not started the car yet, the field

acts as a ground and power flows through the light and out to ground -

lighting the bulb so you know it works. Once you start the car, the voltage

at the field is powered internally by the output of the alternator. If this value

is exactly the same as the battery voltage, then you have the exact same

voltage on each side of the indicator light and they balance each other out -

kind of alike a tug of war in reverse. If all goes well, the light never comes

on, and you drive happily around knowing all is well with your alternator. If

the output of the alternator should drop due to a slipping/broken belt or due

to certain kinds of electrical faults inside the alternator itself, there will be

less voltage on the field side of the light and more voltage on the switched

ignition side of the light. The result is that some amount of electricity will

flow through the light and into the field and the light will glow proportional to

that voltage difference. This is how a slipping belt or an overloaded

alternator will cause the light to glow very dimly, while a full-on failure will

cause the light to glow very bnghtly Note that if you disconnect (or forget

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to connect) the wire at the alternator, the light will never come on and the

alternator may not charge properly.

The dashboard indicator light circuit also typically has an extra wire with a

calibrated resistance in it This wire is run in parallel to the indicator light

and has about a 1 Oohm resistance. It's purpose is to allow slightly more

current to flow to the alternator field current system at initial start-up to

make sure the alternator begins producing power as soon as the engine

starts. About 1 amp total current is flowing to the field current between the

light and the resistance wire, with the resistance wire supplying about 3/4

of an amp. This extra resistance wire does not affect the functionality of the

indicator light in any way.

6. 7 Conversions And Customization

Many "hot rod" style conversions use a modified internally regulated

alternator to eliminate the two small wire connections and only leave the

single large BAT connection to be hooked up. This is usually referred to as

a "one wire" alternator - you only have to run one wire to it instead of the

usual three wires. In this conversion, the dashboard indicator light is

eliminated entirely. the field terminal is connected to the BAT terminal

mternally. and the connection to the other terminal is made inside the

alternator. Conceptually, this conversion works like a factory system

without the indicator light on the dashboard and with the remote voltage

sensing wire connected to the back of the battery. There are several major

drawbacks to this setup One is that you have to to rev the engine up to

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approx 1100rpm once after the engine is first started for the alternator to

begin charging - the alternator has to reach a high enough RPM so that it

"self-excites". Another is that the field connection inside the alternator can

allow a small current draw while the vehicle is not running, and this can

cause a dead battery if the car is stored for a period of time. Lastly, you do

not have the advantage of the remote voltage-sensing feature and that

means poor electrical system performance - dim headlights, slow wipers,

and various other maladies. There are some great details on this at the

MAD Enterprises website - check out their articles on the remote sensing

feature, 1-wire vs. 3-wire alternators, and a great description of a typical

muscle car-era Chevy charging system for more details.

I personally do not recommend the "one wire" conversions - the dubious

improvement in under hood aesthetics just isn't worth it. Your neighbors will

probably not appreciate you revving your car up to 1100 rpm each morning

at 7am before you head out to work and it makes your otherwise cool ride

annoying to drive. Many "tamer" drivers (like your wife, if she's anything like

mine) will often start the car and drive for some time before making it to

1100 rpm for the first time. During that entire time, she would be draining

the battery if the vehicle was using a "one wire" conversion - and that's not

cool. It is very simple to hook up the extra wire for the indicator light and it

makes the car much more pleasant to drive - you have one less thing to

worry about when you just want to get in the car and go. In addition. many

of the vehicles that use the 1-w1re conversion tend to be spec1alty use

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vehicles and thus do get stored for a long time between uses, so the

battery drain could be an issue. If you do go that route, consider a battery

disconnects or some form of "battery maintainer" to keep your battery

charged between vehicle uses. Lastly, the problems with reduced voltage

as a result of not having the remote voltage-sensing feature can be a very

big deaL

If you are still pondering a "one-wire" conversion, it should be noted that

you could partially eliminate the second wire by using a short pigtail to

hook it directly to the BAT connection on the alternator. If you examine the

diagram above for an internally regulated alternator, you will see that this

wire eventually ties back into the wire that is attached to the BAT terminal

anyway. A final word of caution is to think twice (and then think about it

again) before deviating frorn the way the factory did things if you want to

customize your charging system. Modern factory charging systems are

amazing reliable and trouble-free. There is a reason the factory did what

they did. Adding those extra lengths of wire probably costs them about $1

a car - and although that may not sound like much, when you make a

million cars. $1 per car is a $1,000,000 less in potential profits. That's some

serious money - and that's just for a few pieces of wire. (This detail is why

the factory goes crazy trying to save every penny possible when building

the car - rt really adds up fast and they like making all the money they can.)

Also. when you make a mrllion cars and find out something is wrong with

them (frre hazard. doesn't always charge the battery, etc.) it ends up being

16X

very expensive - both in real dollars and from a public-relations perspective

-to repair the problem. Melding two factory-style systems to upgrade your

vehicle to newer standards is a worthy goal and often a very easy thrng to

do - just be sure you get all the details right so you can enjoy your vehicle

for many trouble-free miles to come. Take the time to make sure each wire

you put into the car or change the function (aka, push more current through

it) is up to the task you are placing before it.

6.8 History

In recent trend reducing pollution is an important task. In metro cities where

large number of vehicle are on road creates heavy pollution. To overcome

these, different steps are being taken. One of the steps is use of electrically

driven vehicle. It produces very less amount of exhaust emission and

produce less amount of pollution. But there is a draw back of electrically

driven vehicle. It runs for shorter period and can travel shorter distance.

Again recharging to be done and have to wait for certain time for charging,

charging is possible through 15 amp socket. This facility is available at

different charging station. There may be alternate arrangement are to be

made for switching over to Petrol/ Diesel for recharging the vehicle in case

of emergency. The drawback of short duration running is great

disadvantage of electnc vehicle. A new approach is being made to

1ncrease the duration running period by recharging the Battery with some

add1t1onal device f1tment 1n the vehicle without power loss and without

losing any engine efficiency. The rechargeable facility will be in-built to the

vehicle. No connection to be taken from Engine shaft for running the

dynamo for charging the battery.

6.9 Design Aspects

The vehicle, which is presently running with electric power, is REVA, which

is produced by REVA Pvt. Organization, Bangalore and marketing slowly to

the other states. Due to short duration running the market is not responding

highly. Customer does not satisfy the running aspects. Now little

modification are being suggested to increase the duration by recharging

the battery with the help of Dynamo fitted in the vehicle by belt running

along with the shaft. There is a Fan to be fitted in front of vehicle (not

protruding outside) through forward motion with are resistance a heavy

amount of wind is being sucked and passes through the Fan blade and try

to rotate with high RPM. When RPM increased connect the Fan belt to the

dynamic with suitable arrangement shown in fig. Dynamo starts charging

the battery with the help electrical circuit. The battery will be getting

charged. During higher speed of vehicle charging process will continue.

When applying breaks lowers the speed the charging of battery is to be

discontinued by puttmg a Relay/ Cutout along with sensor of speed. When

the speed lowered at 1 000 RPM the relay will disconnect the charging

process further the system will maintain normal running condition. But

when the speed mcreases more than 1000 RPM the relay will energize the

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electrical circuit the charging continues. This process can continue for a

long period of running the engine & increasing engine efficiency. Two-block

diagram shows the complete design process along with engine running

condition with different speeds.

Switch Electrical Motor

48 V Battery

Fig. - 6.3 Wiring diagram of normal condition in Electric vehicle

Switch Electrical Motor

"" ..--------c~-/1-/'·_ •. =r-

48 V Battery -]

Relay (Cut out) 1-L__f-----2)..-Fan Belt

Dynamo

Fig 6.4 Modified Wiring Diagram of Electric Vehicle

6.10 Accessories Of Modified Design

Cut Out/ Relay Sensor: -

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Sensing Relay to be used which sense the speed/RPM. At increased RPM

it energized the circuit allow the current to go to Battery. At decrease RPM

it de-energize the circuit.

Battery: -

48V. 200amp/hr EV tubules lead acid battery, which is used to rely the

vehicle with the help of electronic starter, charge times 2.5 hours up to 80%

and 100% in 6 hours and range is 90km per charge. Top speed can be

mamtained 50 kml hr & range is 95 kmlcharge

17~

Dynamo:-

When dynamo is running current cannot flow through the shunt winding. It

produces a magnetic flow that overcomes the spring tension so causing

the contacts to close and can passes the current to charge the 48V battery.

Motor:-

It is having high torque (70Nm) separately excited DC motors 13kw peak

power capacity. 400 Amp. microprocessor based with regenerative

braking, 220V-2.2kw high frequency switch mode type charger. EMS is

microprocessor based battery management system.

Fan:-

Cooling Fan, which can rotate with forward Air resistance free to rotate with

high RPM without any friction losses.

Belt Pulley: -

Belt Pulley connected with fan shaft to rotate the Dynamo shaft to produce

electricity and can charge the 48V battery to increases the power direction.

Clutch shaft: -

Wh1ch is used to connect the belt shaft along with Fan shaft with increased

RPM. At lower RPM it should disconnect the belt shaft from Fan shaft Fig.-

3 shown the arrangement of shaft assembly to connect fan shaft.

IT\

Battery I I Fan Shall -L _Q C'ut Out -- 0 Fan

I I Clutch Shaft

-0---- ---

Dynamo Shaft

Fig.-6.5: Wiring Diagram of Shaft Assembly

6.11 Safety Aspects

Safety:

The specially designed Steel space frame and side impact beam cocoons

passengers in the event of a collision, shielding them from an impact. The

body of the Reva is made of high impact ABS (Acrylonitrile Butadiene

Styrene) that is dent resistant and non-corrosive.

This ensures minimum damage to the car and enhances protection to

passengers in the event of a collision. Hit the Reva's ABC body with a

hammer and it will not dent. Unlike steel, ABS bounces back into shape.

Eco-friendly:

Being an Electric Vehicle. Reva is zero polluting and noiseless. It does not

require frequent oil changes. Moreover Reva has high recyclable content.

High on Technology

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Two computers and the state-of-the-art electronics in the Reva provide an

efficient energy management system with advanced computerized vehicle

diagnostics.

The regenerative braking in the Reva recovers useful electricity by putting

it back into the batteries. Regenerative braking lets the motor act as a

generator, converting the vehicle's momentum into electricity.

Prime Mover:

The prime mover in REVA, is the motor. It is similar to the engine in a

conventional car. Reva has a 13 kW separately excited DC motor with a

high torque of 70 kW separately excited DC motor with a high torque of 70

Nm at zero speed. When in use, the motor converts the energy stored in

the Power Pack into mechanical motion. The high torque electric motor

ensures a quick acceleration. The power from the motor is delivered to the

wheels through the Trans-axle that propels the vehicle. While braking, the

motor acts like a generator and recharges the Power Pack.

Power Pack:

Power Pack consists of e1ght 6-Volt EV tubular type lead acid batteries that

attain 80% state of charge in under 2.5 hours. A complete charge is

achieved in less than s1x hours. The Power Pack is housed beneath the

front seats. which lowers the center of gravity, thus increasing the safety of

passengers. Charging REVA is a safe and easy process- Just plug into a

220 Volt. 15 Ampere socket - at home or at work.

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Charger:

It converts AC into DC power to charge the power pack. The charger is

computer controlled with an in-built stabilizer and auto shut-off mechanism.

The smart charger's output is connected to the power pack and ensures

that optimum current and voltage is maintained at all times.

Computerized Motor Controller:

This regulates the flow of energy from the Power pack to the Motor in direct

relation to pressure applied on the accelerator. It ensures perfect speed

control and optimum use of energy in both forward and reverse directions.

The brain of REVA is the Energy Management system.

Energy Management System:-

It monitors and controls all vital functions. The EMS is a computer based

system that optimizes charging and energy output of batteries to maximize

operating range and improve performance. The system also predicts

available range for a given state of battery charge and is a standard feature

on the Reva.

The EMS also maintains an electronic log of the vehicle performance,

enables service personnel to run diagnostic checks on the car to give

service information about the car.

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6.12 Result and Discussion

To obtain zero pollution or to reduce the pollution this type of electrically

driven cars are most suitable in the market or in metro cities. To increase

the duration suitable suggestion are being with the help of additional device

fitment. By this additional fitment cost will increase about 5% of total cost.

But the increased power-duration and increased length of period of running

will be 30% increased with the engine efficiency. Hence these systems are

most suitable to save the earth for global warning.