Electrical Vehicle Presentation A to Z

FUNDAMENTALS OF ELECTRIC VEHICLE: TECHNOLOGY AND ECONOMICS
Department of Electrical Engineering
NATIONAL INSTITUTE OF TECHNOLOGY DURGAPUR
(An Institute of National Importance under Ministry of Education, Government of India) 1
PROFESSOR & HEAD
HIGH VOLTAGE & INSULATION LABORATORY
DEPARTMENT OF ELECTRICAL ENGINEERING

18-05-2021 NATIONAL INSTITUTE OF TECHNOLOGY DURGAPUR 2

Where is the problem to switch to EVs?
Batteries: energy-storage
Weight, Volume, Cost (all related)
Weight and Size: Energy Density (gravitational and volumetric)
Unit of Energy: Watt-hour (1 Watt of power for 1 hour) 30 Watt bulb used for 1 hour consumes 30 wh of
energy
Unit of energy used for electricity metering: 1 kWh is 1000 Watts used for 1 hour, or 100 Watts for 10 hours
A small Indian home consumes about 2 units of electricity in a day
Gravitational Energy Density: Watt-hour per kg

Li-Ion Energy density continuously increasing
Gravimetric ED of NMC and NCA cells is in between 250 to 300 Wh/kg today LFP cell density saturated at
150 Wh/kg: theoretical limit of 160 Wh/kg
Towards 400 to 500 Wh/kg in coming years: NMC with Graphite-Silica anode
Volumetric Energy Density of NMC cells touching 500 Wh/litre Other variants of Li-battery may emerge to
drive energy density higher

How to compute: Cost per kWh of usage?
Cost of storing a kWh of energy and then draw out and use How many times the storage be used: Cycles
Will the size of storage reduce as one keeps cycling
Has to take into account Capital costs: depreciation + interest
Will require an understanding of lifetime of usage to compute effective depreciation and interest
Operational costs including fuel costs
Can one learn to compute cost per kWh of usage?
of different types of energy storages (and compare with cost per kWh And of course the environmental costs
(end to end): often ignored
Can it use fully renewable technology?

Battery Swapping Advantage
Separate vehicle business (without battery) and energy business
 (Energy Operator)
 Capital cost of vehicle similar to that for petrol / diesel vehicle
 Operation cost today same as petrol / diesel vehicle WITH limited SUBSIDY, electric autos and buses can
compete today with ICE vehicles
 Volumes for public vehicles would make them highly affordable Get Fleet Operator company to buy
vehicles in bulk and lease
Get Energy Operators (EOS) to buy batteries in bulk and set up energy business

Battery-life: depends on multiple factors
Number of charge-discharge Cycles of a battery depends on
Battery-Chemistry used (manufacturer dependent)
Rate of Charging and Discharging (higher rate reduces life)
Usage Temperature (above and below 25°C hurts life)
Operation-region of charge-discharge (Depth of Discharge or DoD) used
Calendar-life
State of Health (SoH) is a measure of Battery Capacity remaining (as compared to initial Capacity) as the battery is used
 A EV battery at End of life (EOL), when its capacity reduces to 75% or 80% of initial capacity Will limit vehicle range to 75% to
80% of the initial Range when battery is near Eol

Typical Battery-life and charging
Battery life dependent on Rate of Charging
Battery life best when charged slowly (four to six hours at 25*C)
Fast charge (in one hour or less) impacts battery life
Typical battery life: 500 to 2000 charge-discharge cycles (slow-charge)
Battery with 500 to 1000 cycles costs low
Battery with 1500 to 2000 cycles quite common and is medium costs Battery with 3000 to 4000 cycles or
more costs high
Batteries with capability of fast charge / discharge costs much higher

Does Charging / Swapping need Standardisation?
What standardisation is a must?
Connector: plugs and sockets
Voltage, Current and Maximum Power
Communication to vehicle?
Communication with Energy Supplier: Charging Operator or Utility Manager
Metering: how does one bill customer?
Protection

Battery Swapping
EO sets up Battery Swapping Infrastructure at convenient locations Enrols customers who would lease
EO's swappable batteries for their vehicles
Will swap a discharged battery with a charged battery at any of the locations anytime
EO purchases and owns batteries
Has Bulk Chargers at these locations to charge the incoming discharged batteries and offer
charged batteries to customers enrolled Customers pay for Energy Used in the batteries
Charges will take into account depreciation and interest costs for purchased batteries, infra-costs,
electricity cost and operations cost, besides EO's profit

Li lon Batteries for EV
Battery-pack design
thermal design for Indian temperature and driving conditions
Low-cost Cooling mechanism to withstand 45 C ambient
Mechanical design to ensure cells do not bulge on Indian roads Battery Management Systems to get the
best out of each cell
Safety is a major concern: handled by BMS

Materials for Batetries
Li-Ion batteries today use
Lithium, Cobalt, Manganese, Nickel and Graphite - India does not have much of the mines for any these
Import bill could sky-rocket : 25 GWh per year by 2025
Recycle used batteries (urban mining)
 90% of Li and Co, Ni, Mn and Graphite being recovered Need number of recycling plants with ZERO
EFFLUENT
India could import used Li-Ion batteries and become the urban-mining capital of the world
100K ton battery waste available in India today: 20 GWh of batteries

ICE drive-train to EV drive-train: common parts
•Body/frame: Body and frame of the existing ICE car
•Doors & power windows: Existing
•Wheels: All wheel components including the rim, hub,
knuckle, tyres
•Suspension system: Existing system including the lower arm
and the struts
•Power Steering system: hydraulic to electric
•Power Braking system: hydraulic to electric - Vacuum
pump to actuate the braking system
•Safety system: All airbags and parking sensors
•Wipers & fluid pump: Existing viper liquid pump &
vipers
•Mirrors: Electronics/Manual mirrors
•Interiors: All interiors including seats, seat belts, A/C
vents, Cabin lights and other interior components

ICE to EV: to be added
•Electric Motor: High performance electric motor
used for traction
•Motor Controller: Motor controller for motor drive
with closed loop feedback system
•Transmission system: High efficiency transmission
system with reduction system for high acceleration
•Battery Pack with BMS: Reliable battery pack with
BMS with CAN
•Communication and support loT and telematics: loT
for vehicle data collection combined with latest
technology telematics & data infrastructure to
monitor & manage vehicle
•DC-DC Converters: Efficient DC-DC converter for
other peripherals
•Vehicle control unit/ Master control unit: A
dedicated VCU/MCU for vehicle management and
safety

ICE to EV
Parts & Components to be Modified
Air conditioning system: Integration of
variable speed DC motor for existing hydraulic
actuated AC compressor
Cooling system: Can be reused for motor &
cooling with electric water pump integration
Dashboard may need some modifications
Parts and components to be removed
Fuel tank and associated connections Engine
and associated connections like sensors
Clutch & transmission: to be removed since a
single speed transmission system used ECU
and Connections other sensors
Fuel pump and other engine subsystems

Future: Technology tasks to be pursued
•Efficient Regeneration: recovers energy during
deceleration, braking, descending mechanical
energy converted to electrical energy, to be driven
back to battery
•Needs motor design to recover as much energy as
possible
•Can regeneration efficiency come close to 90%?
•Vehicles will then only use energy to overcome
rolling-resistance and aerodynamic drag
•Materials for light-weighting vehicles
•Materials for better insulation to reduce heat-load
air-conditioning competes with drive train for
battery power*
•Better tyres and better aerodynamics
•enhances energy-efficiency of EVsVehicle
•Controller and Software, Integration and testing
•Can we gainfully redesign every part of IC engine
vehicle as it changes to Electric?

WAY FORWARD
Time is of essence: In four years, may be flooded with imported EVs / subsystems
We have two years time to design and manufacture EV subsystems
What can be done in first year, second year and third year? Not JUST development, but
commercialise and SCALE
What does Start-ups and R&D personnel in educational Institutes/ R&D centers have to do?
How do industry-academia work together?
What do we need from the Government?
Can we do it by 2030: Certainly

Driving an ICE or Electric Vehicle
How much Power is required to drive a vehicle?
How much Energy is required to carry out a road-trip?
What is the composite mass of the vehicle (including passenger and goods): Gross Vehicle Weight
(GVW)
What is the condition of the roads (rolling resistance)
What is the aerodynamics of the vehicle (Aerodynamic drag)What is the incline that it needs to
traverse? (Gradient Resistance)
What are the velocities and accelerations at different points of time (Drive Cycle)
What is the maximum speed and maximum acceleration of the vehicle?

Traction Force is given by
Ftrac = Acceleration Force + Aerodynamic Drag + Rolling Resistance + Climbing Force
Force=(M*a)+(12*p*Cd*A*V^2)+ (M*g*μCosθ) + (M*g sinθ), where a is the acceleration and is
dv/dt
The energy consumed by vehicle in motion is the integration of Traction Power Energy =
INTEGRATION OF Ptrac *dT Per day in Watt-sec and is converted to kWh by dividing by 3.6
Vehicle may have regeneration, which converts deceleration of vehicle while climbing down or
otherwise applying brakes (using Regenerative Braking) into Regenerative Energy
Thus net energy consumed is R Energy, where R is regeneration efficiency As Regeneration factor
is typically 15% to 30%, R is (1-RegenFactor) or typically 0.85 to 0.70

Modal calculation for 3 wheeler

Compute Distance and Energy for the full drive-cycle
Take velocity at every small interval AT (say 1 second or even lower) and compute in a spread-sheet
distance: Vel (m/sec) AT (sec) at each point
Acceleration = LEVel / AT in m/sec2
Acceleration Force F, = M Acceleration (Newtons)
Rolling Resistance Force F, = M*8’u
Drag Force Fo = 0.5' Cd p A v?
Traction Force Furac = F, +F, + Fo (Newtons)
Traction Torque (Nm) =Firac * wheel radius (m)
Pirac(Watts) = Furac V (Nm/sec)and
Pu(Watts) = (R F)V with Regeneration Efficiency R, when Frac is-ve

Gears multiplies Torque
A IC engine typically gives less torque than a vehicle requires A gear is used to multiply engine
torque by N
Vehicle Torque = N* engine torque At the expense of rpm:
Vehicle rpm is reduced by n or Vehicle rpm = engine rpm/n
Vehicle power is same as engine power
Similarly in a EV Vehicle is connected to a motor using a gear of ratio of n:1
Vehicle Torque = n * Motor Torque
 Vehicle rpm = Motor rpm /n
Thus Motor Torque can be multiplied at the expense of Motor rpm

Do we use multi-gear or Changeable
Gear
Multi-gear or changeable gear can change gear-ratio to different values Gears changed using a
clutch which temporarily disengage gear from motor Common in all ICE vehicles
But EV motors are usually designed to work efficiently with a large range of speeds and torques
It normally uses a single FIXED gear
That would be the preference, as long as one can meet all vehicle requirement with the motor
and a fixed gear
Power does not change with gear-ratio

Battery Energy (Capacity)
Battery designed for certain Energy (C) in kWh V* Ah /1000 Comes from cell capacity defined in
Ampere-hour (Ah) Defined in terms of nominal voltage (V) and (current hours) or Ah rating
For long-life of rechargeable battery, it is never fully emptied or fully charged Leaving certain
energy at the bottom during discharging and at the keeping it empty at top
Useably energy each charge-discharge cycle is typically x% (may be 85%) of total capacity
Also, Battery Capacity reduces with each charge-discharge cycle
When battery capacity remaining is y% (typically 80%) of initial capacity, the range gets
proportionately reduced. battery life for EV is OVER and it needs replacement
So at end of its cycle life, useful capacity = x*y*C = 0.8*0.85C = 0.68C

Battery Power
Even when batteries have sufficient energy, rate at which Power can be taken out of battery
(discharge rate) is limitedC-rate
Higher rate discharge impact the life-cycles of the battery Same is true about charging
behaviour: higher charging rate impacts life Higher rate charging - discharging also heats up the
battery
Battery has to be designed to have peak-power capability that the vehicle Rate dependent on
size of the battery as well as the nature of ce

EV Auxiliary
EV Auxiliary:
lights and auxiliary motors
Vehicle Control Unit
Head-lights, tail-lights, flash-lights, vehicle-interior lights
Motors for wipers, windows
Entertainment and Guidance Other Electronics, Communications, Sensors, Rear-view
projection
All use Low-voltage Power: from Battery through DC-DC converter(s)

Vehicle Control Unit (or MCU)
Communicates with Battery and with Controller
Typically over CAN May have external wireless Interface
 May also have other interfaces / sensors: GPS, Load-sensors, inclination sensors etc.
Manage Motor and Controller Collects Data during drive
Possible to download certain parameters on to motors / batteries Like Geo-fencing, Limiting
temperatures for operation, limiting Speeds

Understanding Battery Parameters
Consider a Battery of 48 Volts with a Capacity C of 15 kWh Ampere-hour (Ah)Battery capacity
can also be defined byits
Battery Ah = C/voltage 15000 Wh/48V= 300 Ah
or a
Battery C = Battery voltage * Battery Ah
State of Charge (SoC) of battery is a measure of percentage of battery charged SoC of 0% means
discharged battery: SoC of 100% is fully charged battery (having 15 kWh energy)
Output Voltage of a Battery-pack varies with its SoC For a 48V Li-Ion battery, voltage varies from
43 to 56V depending upon the State 43V when SoC is near zero and 56V when SoC is near 100%

Battery Life
Consider a battery with a capacity of C to start with; Over time the capacity decreases due to
Aging or time: Calendar life (typically 1% to 2% of capacity loss per year) Charge-discharge
cycles: as batteries are charged / discharged, battery capacity decreases Battery Life
When the capacity becomes 80% (or 70%) of C, it may be termed as End of Life of battery
implying the battery will no longer give range required by EV and therefore needs to be replaced
For 15kwh battery: End of life capacity is 12kWh (80%) or 10.5 kWh (70%) these batteries can
no longer be used in EV's as the range decreases, but may be considered for other applications
(second life of the battery)

C-Rate of charging - discharging
The C-rate is a measure of the rate at which a battery is being discharged. It
is defined as the discharge current divided by the theoretical current draw under which
the battery would deliver its nominal rated capacity in one hour. A 1C
discharge rate would deliver the battery's rated capacity in 1 hour
2C means rate would deliver the battery's rated capacity in 30 min.
0.2C means rate would deliver the battery's rated capacity in 5 hrs.
Similarly .5C means rate would deliver the battery's rated capacity in 2 hrs.
Fast charging is when charging is getter than or equal to 1C.
Slow charging is when c rate is less than 1C.

Battery manufacturer guarentees
Life of a battery-pack is primarily dependent on life-cycle of the battery-cells Cycle-life of a
battery cell is a fundamental parameter, depending upon its chemistry,
but also on many other factors such as
C-Rate of charging – discharging
Temperature of its charging - discharging and also its storage temperature
Depth of discharge (DoD): % SoC left at top and bottom Most Li-Ion battery functions best (have
maximum number of life-cycles)when its temperature of its usage is 25°Cwhen its C-rate is less
than 0.10 when battery charge-discharge is in between SoC of 10% and 80%
A Li lon cell manufacturer guarantees 1000 cycles under the conditions like 1000 cycles when
charged at C/2, discharged at C rate @ 25°C with 85% DoD

BATTERY PACK DESIGN

Key Parameters
key Parameters
1) Soc
2) DoD
3) EOL
4) C-rate
5) Cycle Life
6) Aging : Calendar life

Uses and specification

Typical battery size and Fast Charge
Need to look at traction power needed for the vehicle
2-wheeler battery size: 1 kWh to 3 kWh
E-rickshaw battery size: 2.5 kWh to 5 kWh
E-auto battery size: 3 kWh to 6 kWh +
Small Car battery size: 15 kWh to 30 kWh
Large Car battery size: 30 kWh to 75 kWh
Bus battery size is 100 kWh to 400 kWh
Thus a 10 kW charger is FAST for 2-wheelers and 3-wheelers
But SLOW for all 4 wheelers and busesA 20 kW charger is FAST for 2W, 3W and small 4W, but
SLOW for large 4W and buses

Standardisation efforts in the World
Japan Started early for standardizing EV Charger with Cha-de-mo (let us go for a cup on tea)
DC Chargers were first standardised China follower with GB/T Dc charger standards
 coming later than Che-de-mo more comprehensive protocols and updated features Europe came
still later and proposed more advanced EV Charging Standards
CCS was first standardised as DC Charger later updated to CCS-2: incorporated Grid to Battery
Charging protocols still later
USA came in late and have adopted a mix of European and Japanese standards
AC Charger standardised by Europe, USA and Japan Level 1 AC Charger with no communication to
vehicle or to the grid
Level 2 AC Charger with communication to vehicle, but communication to grid not there.
higher power DC Chargers with communication to vehicle and to the grid specified

Ev power train

Chargers and Power-electronics
Chargers with poor efficiency and Low power-factor are inexpensive –
Would waste power during charging: in long-run more expensive
Advances in Power-electronics have made these chargers efficient with power factor
correction, small in size and low-weight in recent years
AC power after rectification is converted to high-frequency signal
Small high-frequency transformers are then used to reduce / increase voltage levels to desired
level
Rectification is then carried out to get the desired DC voltage
The control is entirely by Software

Low Voltage DC Fast Charger DC001
Key Functions
Adaptive and Controlled charging Protection and safety measures
Vehicles2-wheeler, 3-wheeler and small and medium sized 4-wheelersthat's a three-phase ac uh
works till about 10
Output 18 or 72 V DC, 15 KW
Low Voltage Charger Specifications
Input : 3 Phase AC Output: 48V @ 10 kW (42V to 56V) or 72V @ 15 kW (63V to 84V)Power-factor of
0.90 for full load or more
Physical Layer Communications EV- EVSE: CAN
EVSE - CMS: 2G/3G or Ethernet broadbandHand-held- CMS: 2G/3G wireless EVSE –
Payment Gateway: 2G/3G or Ethernet

Bharat Charger AC001: Metering Console
Input
Charging rate: up to 3 kW
AC Supply: 3 phase, 5 wire AC (3 6+N+ PE) Nominal Input Voltage is
415V (+6% and -10%) as per IS 12360
Input Frequency is 50Hz + 1.5 Hz
Input Supply Failure back-up: Battery backup for minimum 1 hour
for control / billing unit. Data logs should be synchronized with
CMS during back up time, in case battery drains out
Communications
Between EVSE and CMS: HTTP communication using OCPP
is what you would see in most Output
Three vehicles charging simultaneously, 15A current each
(PF of vehicle charger to be high)
230V AC (+6% and -10%) single phase as per IS12360
Double-pole breaking RCD (IEC 60309 Blue connector) of
less than 30mA (as per section 7.4 of AIS 138 Part 1)
recommended
Output selection: breaker energized in sequence
one round of all three phases before second round Socket
readiness: LED to indicate socket ready
Isolation: Charger shall comply to class 1 or class 2
insulation class as defined in AIS 138 Part 1, clause 3.3.1
and 3.3.2

Is the Grid ready for EV Chargers?
Chargers and Bulk chargers loads the grid: is grid ready for wide-spread proliferation of EV
Chargers
Depends on power that chargers draw: Slow Chargers of 300 Watts to 3 kW-Grid is like other
household loads like refrigerators to air conditioners to washing machine, grinders
Two problems with higher-rate Charging
•Distribution lines may not be capable of letting such power withdrawals by Fast Chargers /Bulk-
chargers Peak power requirement may be difficult to meet as more and more Fast Chargers
•Manage peak power requirement using pricing: ToD (or Time of Use) metering Also, grid may
chose to limit power output of EV chargers during certain times

Role of various agencies

References
IEEE Electrification Magazine: https://ieeexplore.ieee.org/document/8546812Blog
 "understanding the EV Elephant": http://electric-vehicles-inindia.blogspot.com/WRI-CBEEV
 Report: 'A Guidance Document on Accelerating Electric Mobility in India
https://wri-
india.org/sites/default/files/Accelerating%20electric%20mobility%20in%20India_WRI%20India_
CBEEVIITM.pdf
NITI Aayog Report: Zero Emission Vehicle(ZEV): Towards a policy Framework

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