Model S – A Game Changer of
Electric Vehicle
Yih-Charng Deng (鄧益常)
Technical Fellow, Crash Safety, Tesla Motors
Weilin Chang (張維麟)
Engineering Manager, Power & Vehicle Electronics, Tesla Motors
Transportation Issues Facing the Human Race
• Global automobile population > 1 billion in 2010
(Ward’s Auto report)
• Will double by 2030
• Not sustainable (petroleum & capacity for
production, greenhouse gases emission)
• Sperling & Gordon, 2009, Two Billion Cars:
Driving Toward Sustainability
– Vehicle transformation (hybrid, electric, etc.)
– Fuel transformation (biofuel, hydrogen, etc.)
– Mobility transformation (rapid mass transit,
telecommunication, etc.)
History of EV
•
•
•
•
In 1900: 40% steam, 38% electricity, 22% gasoline
In 1920s, IC engine vehicles started to dominate
Air pollution problems in major US cities
1990 Clean Air Resources Board (CARB) of CA &
Zero-Emission Vehicle (ZEV) mandate
• EV1 from GM
• ZEV abolished in 2003, EV1 program terminated
by GM
Fuel Economy Drive
• 1975 – Corporate Average Fuel Economy
(CAFÉ)
• 2007 – Energy Independence and Security Act
(EISA), 35 mpg by 2020
• 2009 New Fuel Economy Proposal – 35.5 mpg
by 2016
• 2011 US Government Agreement w/ 13 Car
Manufacturers – 54.5 mpg by MY2025
• Hybrid vehicles and new wave of EV
EV Advantages/Disadvantage
• Higher efficiency (80%), 3 times that of IC engine
• Energy chain (source to wheels) – EV is 10-30%
more efficient (expect to increase)
• Can use clean energy source at power plants
(solar, wind, hydro)
• Current EV’s < 100 miles range
• 2012 Model S from Tesla Motors
– Over 300 miles range
– 0 to 60 mph in 4.4 sec.
Electric Vehicle Powertrain
Type of EV
Electric
Propulsion
System
Energy Storage
System
(Primary)
Battery EV
All Electric
Motor
Battery Pack
Fuel Cell EV
All Electric
Motor
Fuel Cell
Hybrid
Motor
(ICE as
generator)
Extended
Range EV
Battery Pack
Energy Storage
System
(Secondary)
Electrical Charge
Vehicle Model
External Power
Tesla Roadster,
Source &
Model S, Nissan
Regenerative Brake
Leaf
External Power
Gasoline Tank for Source, Regenerative
Generator
Brake & Generator
(ICE)
Plug in EV
Hybrid
Motor & ICE
Gasoline Tank
Battery Pack
External Power
Source &
Regenerative Brake
Hybrid EV
Hybrid
Motor & ICE
Gasoline Tank
Battery Pack
Regenerative Brake
GM Volt
Fisker Karma,
Toyota Plugin
Prius
Toyota Prius
EV Energy Efficiency
Electric Vehicle Efficiency
Internal Combustion Vehicle Efficiency
Hybrids and Plug-In Hybrid Vehicle Efficiency
All Electric Powertrain
• Energy Storage System (Battery Pack)
• Propulsion System:
– Motor
– Gearbox
– Inverter
• Charger
Battery Design
• Cell:
– Cell selection
– Energy & power density
– Cycle and calendar life
• Module:
– Safety protection technology (open, short & propagation)
– Voltage balancing
– Package density
– Isolation and thermal management
• Battery Pack:
– Safety protection circuit
– Lightweight & durability
– Design for quick swap
Battery Cell Form Factor
• Cylindrical Cell:
– Good cycling ability, mechanical stability,
economical for manufacturing
– Heavy and relative low package density
• Prismatic Cell:
– Optimal use of space by using layered approach,
improving space utilization, and allowing flexible
design to achieve higher package density, the
metallic housing providing mechanical stability
– More expensive, less efficient in thermal
management, shorter cycle life
• Pouch Cell:
– Simple, flexible and lightweight solution to
battery design, highest package efficiency, costeffective for manufacturing
– Swelling factor, shortest cycle life and less
durable
Cell Chemistry
Why Lithium-ion
• Advantages
– Today’s lithium-ion cells have the highest density w/ a good
balance of power density
– Relatively low self-discharge, less than half that of NiCd and
NiMH
– Low maintenance, no periodic discharge needed
– No memory effect
• Challenges
– Requires protection circuit to limit voltage and current
– Subjects to aging, even if not in use
– Transportation regulations when shipping in larger quantities
– Higher cost
Lithium-Based Battery Comparison
Li-cobalt
Li-manganese
Li-phosphate
NMC
Voltage
Charge limit
LiCoO2 (LCO)
3.60V
4.20V
LiMn2O4 (LMO)
3.80V
4.20V
LiFePO4 (LFP)
3.30V
3.60V
LiNiMnCoO2
3.60/3.70V
4.20V
Cycle life2
500–1,000
500–1,000
1,000–2,000
1,000–2,000
Operating temperature
Average
Average
Good
Good
Specific energy
150–190Wh/kg
100–135Wh/kg
90–120Wh/kg
140-180Wh/kg
Specific power
1C
10C, 40C pulse
35C continuous
10C
Specifications
Safety
Average. Requires protection circuit and cell balancing of
Very safe, needs cell balancing Safer than Li-cobalt. Needs
multi cell pack. Requirements for small formats with 1 or 2
and V protection.
cell balancing and protection.
cells can be relaxed
Thermal. runaway3
150°C
(302°F)
250°C
(482°F)
270°C
(518°F)
210°C
(410°F)
Cost
Raw material high
Moli Energy, NEC Hitachi,
Samsung
High
High
In use since
1994
1996
1999
2003
Researchers, manufacturers
Sony, Sanyo, GS Yuasa, LG
Chem Samsung Hitachi,
Toshiba
Hitachi, Samsung, Sanyo, GS
Yuasa, LG Chem, Toshiba A123, Valence, GS Yuasa, BYD,
JCI/Saft, Lishen
Sony, Sanyo, LG Chem, GS
Yuasa, Hitachi Samsung
Moli Energy, NEC
High power, average
Notes
Very high specific energy,
limited power; cell phones,
laptops
High power, good to high
Very high specific energy, high
specific energy; power tools,
specific energy, elevated self- power; tools, medical, EVs
medical, EVs
discharge
Model S Battery
• Equipped with over 7000 lithium-ion 18650 cells to provide
up to 85kWh total energy capacity
• Active liquid cooling/heating thermal management system
• Total weight about 600kg and located underneath the floor,
resulting in low center of gravity for high resistance to
rollover and excellent vehicle handling
• Model S achieves 320 miles range based on EPA-2 cycle
procedure
• Touchsafe quick disconnect for battery replacement or
maintenance
• Multi-layers of safety protection features from cell, module
to pack design
• Capable of supercharge (high current charging)
• 8 years, unlimited miles warranty
Battery Pack Options of Model S
Factors Influence Range
Range vs. Speed
• Model S Cd = 0.24
• EPA 2-cycle: 320 miles
• EPA 5-cycle: 265 miles
• New record for EV
Propulsion System
• Rear wheel drive propulsion system to provide better
acceleration, road handling and no torque steering
• Fully integrated system (motor, gearbox and inverter) to
provide world record power density and reduce transmission
power lose between sub-systems to increase power efficiency
• Liquid cooling system for thermal management
• Significantly less moving parts compared
with ICE resulting in simplicity, reliability,
low material and operation cost
• IP6K9K ingress protection and IP8X
under wading line depth
• Communicate with vehicle through CAN
and generate desired torque based on
paddle position and inputs from other
modules
Propulsion System – Motor
• Three-Phase, four- poles AC induction motor
• Why AC motor (vs. DC brushless motor):
– Cost, no rare-earth metal for permanent magnets
– Efficiency, adjustable magnet field strength
• Performance
– Max torque: 600 Nm (443 lb-ft) during 0-5100 rpm
– Max power: 416 hp (310 kW) during 5K-8.6K rpm
– Top speed: 1600 rpm (130 mph)
– Efficiency: Over 90%
Torque Speed and Power Curve
Vehicle Metrics
Taumax
Electrical
450
400
Power (kW) / Torque (Nm)
350
Pmax inflection
point.
300
250
Pmax Mechanical
200
150
Continuous
Power
100
50
Top Speed
0
0
20
40
60
80
MPH
100
120
140
Propulsion System – Gearbox
• Single speed, oil-cooled, open-differential
transaxle gearbox
• Fixed gear reduction ratio 9.73 to optimize top
speed and range
• No transmission and clutch to reduce system
complexity and cost
• Electrically actuated park brake
• Design challenges
–
–
–
–
High motor rpm
Thermal management
High power and torque
Durability
Propulsion System - Inverter
• Paralleling discrete IGBT’s forming half bridge power
stage to convert DC to 3 phase AC
• Capable of converting AC back to DC to charge battery
during regenerative brake
• Rated at 450A rms continuous current
• Digital controller generating PWM to control switch
• Coprocessor to ensure no misinterpretation of
accelerator paddle position while generating torque
• Continuously monitoring inputs from vehicle and other
modules to determine current needed for desired torque
• Several layers of safety features, hardware & software
Motor Control Algorithm
• Vector control (also called FOC) is a variable frequency
drive control algorithm to control speed and torque of
motor.
• Vector control outperforms other motor control
algorithm (such as Scalar and DTC) because the nonconstant vehicle speed and quick response time
requirements in real driving situation.
• Both direct and Indirect FOC to calculate rotor flux
position
• Produce desirable torque through flux control and
torque-producing current
• Commercial DSP available for vector motor control
(Clarke and Park transformation)
Vector Control Block Diagram
Onboard Charger
• Each box is capable of 10KW charging, up to 31 miles per hour
of charge for Model S
• Option to add 2nd charger in parallel to increase to 20kW
charging capacity (62 miles/hour)
• Single phase, acceptable voltage range from 85-265V at
frequency 45-65Hz
• Trickle charge if power source voltage is greater than battery
voltage
• Peak charger efficiency of 92%
• Maximum charge current at normal condition
– 110V: 20A from power source
– 240V: 40A from single phase power source
• Program charging schedule through vehicle touch screen and
check charging status remotely
Charging Infrastructure
• Universal Mobile Connector:
– 110V, 240V and J1772 public charging station adaptors
are standard to ensure compatibility to different
electrical outlets through different regions or countries.
– GFCI protection
– Communicate charging status and fault condition
through indicator light
– NEMA 4 environment sealed enclosure for outdoor
usage
• High Power Wall Connector:
– Wall-mounted charger to provide up to 20kW charging
capacity
– Enclosure design meets NEMA 3R for environmental
protection
– Draw up to 80A from electrical outlet during charge
– GFCI protection
– Communicate charging status and fault condition
through indicator light
• Supercharger:
– Dedicated industrial graded high speed charge station
– Charge half the battery (85kWh) in 30 minutes
Powertrain Components from Taiwan
Existing Projects:
• Roadster & OEM Programs:
– PEM, Charger, stator, rotor, motor shaft …
• Model S Components:
– Motor steel laminations, gears …
Taiwan Industry Strengths:
• Power and vehicle electronics
• Motor & gears
• Machining, sheet metal & die casting parts
Other Salient Features – Body
•
•
•
•
•
Lightweight aluminum materials for maximum mass savings
Double octagon rails for high energy absorption in crash
High strength steel used in the B-pillars and bumpers
Superb side impact and rollover protection
Structural reinforcement for rear impact protection
Chassis
• Double wishbone, virtual steer axis front
suspension and independent multi-link rear
suspension
• Optional air suspension
Edmunds INSIDE LINE
Interior
• 17” Capacitive Touchscreen
• Optional all-glass panoramic roof
Safety
•
•
•
•
8 airbags
Retractor pretensioners
Load limiters
5 point belt systems for the optional 3rd row
child seats
• Sensors to trigger high voltage battery cut-off
• Extensive CAE in the design and development
phases
Compared with Other Cars
Motor Trend 8/27/12
Automobile Magazine’s 2013 Automobile of the Year Testing
10/9/12:
Model S out-dragged BMW M5 (560 hp, 501 lb-ft torque) in 0-100 mph
race
Tesla Supercharger Network
Tesla Supercharger Network
• 6 locations unveiled on
9/25/12
• Solar carport systems, free
charge for Model S owners
indefinitely
• Slight net positive power
transfer back to the electricity
grid
• More supercharger stations
in the US, Europe and Asia in
2013
Concluding Remarks
•
•
•
•
•
Team dedication
Relentless pursuit of excellence
Open working environment
2012 production all reserved
Extremely positive feedback from customers
and car critics (WSJ, USA Today, Motor Trend,
2013 Car of the Year – Yahoo Autos,
Automobile Magazine)
• A sea change of automotive landscape
THANK YOU