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)

Energy Storage System

(Secondary)Electrical Charge Vehicle Model

Battery EV All Electric Motor Battery Pack External Power

Source & Regenerative Brake

Tesla Roadster, Model S, Nissan

Leaf

Fuel Cell EV All Electric Motor Fuel Cell

Extended Range EV Hybrid

Motor (ICE as

generator)Battery Pack Gasoline Tank for

Generator

External Power Source, Regenerative

Brake & Generator (ICE)

GM Volt

Plug in EV Hybrid Motor & ICE Gasoline Tank Battery PackExternal Power

Source & Regenerative Brake

Fisker Karma, Toyota Plugin

Prius

Hybrid EV Hybrid Motor & ICE Gasoline Tank Battery Pack Regenerative Brake Toyota Prius

EV Energy EfficiencyElectric 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, cost-effective 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 ComparisonSpecifications

Li-cobalt Li-manganese Li-phosphate NMCLiCoO2 (LCO) LiMn2O4 (LMO) LiFePO4 (LFP) LiNiMnCoO2

Voltage 3.60V 3.80V 3.30V 3.60/3.70VCharge limit 4.20V 4.20V 3.60V 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

Safety Average. Requires protection circuit and cell balancing of

multi cell pack. Requirements for small formats with 1 or 2 cells can be relaxed

Very safe, needs cell balancing and V protection.

Safer than Li-cobalt. Needs cell balancing and protection.

Thermal. runaway3 150°C 250°C 270°C 210°C

(302°F) (482°F) (518°F) (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, LishenSony, Sanyo, LG Chem, GS Yuasa, Hitachi Samsung

Moli Energy, NEC

Notes Very high specific energy,

limited power; cell phones, laptops

High power, good to high specific energy; power tools,

medical, EVs

High power, average

Very high specific energy, high power; tools, medical, EVsspecific energy, elevated self-

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

• 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%

Propulsion System – Motor

Torque Speed and Power Curve

Vehicle Metrics

0

50

100

150

200

250

300

350

400

450

0 20 40 60 80 100 120 140

MPH

Po

wer

(kW

) /

To

rqu

e (N

m)

Pmax Mechanical

TaumaxElectrical

Pmax inflection point.

Top Speed

Continuous Power

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 non-constant 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

• 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

Charging Infrastructure

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

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

Compared with Other Cars

Motor Trend 8/27/12

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