benchmarking and teardown activities undertaken on nissan leaf

Low Carbon Vehicle Technology Project

Benchmarking and Teardown Activities

Undertaken on

Nissan Leaf and Chevrolet Volt

Johnathan Breddy, Tata Motors European Technical Centre (TMETC) plc

Agenda

• Benchmarking and teardown overview

• NVH challenges of alternative powertrains

Nathan Gabbott, TMETC

• Thermal benchmarking

David Bridge, MIRA

Car Selection

US-specification Chevrolet Volt

UK-specification Nissan Leaf

Timeline

2011 2012Jun Jul Aug Sep Oct Nov Dec Jan Feb

Leaf 1 Delivery u

Benchmarking2 Delivery u

BenchmarkingTeardown

Volt 1 Delivery u

BenchmarkingVehicle energy efficiency evaluation

2 Delivery u

BenchmarkingTeardown

Benchmarking Activities

• Subjective Assessments

• Aerodynamics

• Braking and vehicle stability

• Parasitic losses

• Discharge behaviour

• Energy efficiency

• Thermal

• NVH

Subjective Assessments

Subjective Assessments – Leaf(Zytek)

Energy Efficiency – Leaf(S Robinson JLR)

Energy Consumption by Vehicle State

(over 2 cumulative NEDCs)

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100%

Acceleration Deceleration Cruise Idle

Vehicle State

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2800

En

erg

yC

on

su

me

d/W

h

Whole Cycle Urban Extra-urban

Time

%

Distance

%

Time

%

Distance

%

Time

%

Distance

%

Accel 27 29 24 28 30 33

Decel 3 3 5 5 1 1

Cruise 43 68 35 67 58 66

Idle 27 0 36 0 11 0

Energy ConsumedUrban NEDC

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erg

y/W

h

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Sp

eed

/kp

h

Cold Urban 1 (0 < t <= 390)

Cold Urban 2 (390 < t <= 780)

Hot Urban 1 (1180 < t <= 1570)

Hot Urban 2 (1570 < t <= 1960)

Scheduled Speed

Energy ConsumedExtra-Urban NEDC

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rgy

/W

h

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ee

d/kp

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Hot Extra-Urban (1960 < t <= 2360)

Scheduled Speed

Energy Efficiency – Volt(Integral Powertrain)

Braking Assessment – Volt(MIRA)

Aerodynamics – Leaf Anti-Drag Lips

Aerodynamics – Under body panels

Teardown

• Completed at JLR Gaydon facility

• Primary objectives

> Permit viewing of EV and hybrid components in situ

> Liberate key components for teardown

Teardown - Nissan Leaf

Teardown - Chevrolet Volt

Teardown - Nissan Leaf Motor

Summary

• Partners able to subjectively evaluate two new to market cars

• In depth evaluations completed in a broad range of activities

• Teardown enabled component level benchmarking

• Cars available post project to support partners and University based tuition

and research

NVH Challenges of Alternative Powertrains

Nathan Gabbott

Principal NVH Engineer

Tata Motors European Technical Centre

NVH Challenges of Alternative Powertrains

Comparison of NVH characteristics of Electric and ICEngine driven vehicles

Specific Challenges in Electric Vehicles

Integration refinement of an APU into the vehicle

Comparison of NVH characteristics of

Electric and IC Engine driven vehicles

EV vehicles bring many new challenges to the NVH engineer:

• Reduced low frequency noise

• Increased high frequency noise

• Reduced load dependency

• Increased road and wind noise sensitivity

However advantages can be found

• Reduced overall levels for improved passenger comfort

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Nissan Leaf exhibits strong whine orders fromtransmission spur gears

Comparison of NVH characteristics of

Electric and IC Engine driven vehicles

Strong lower order content found in the IC engine is absent in the EV drives, reducingoverall level at the cost of a less balanced overall sound quality

Interior NoiseWide Open Throttle

Nissan Leaf IC CompetitorChevrolet Volt

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km/h

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• Both the Leaf and Volt exhibit noise from the power switchingelectronics between 8 and 12kHz

• These switching frequencies present a new challenge in thedevelopment of body sealing and trim packs due to their highfrequency

Comparison of NVH characteristics of

Electric and IC Engine driven vehicles

Interior NoiseWide Open Throttle

Nissan Leaf IC CompetitorChevrolet Volt

Comparison of NVH characteristics of

Electric and IC Engine driven vehicles

Neither the Leaf or the Volt show significant load dependency, this leads to adisconnected feeling from the vehicle.

Interior Noise

Nissan LeafChevrolet VoltIC Competitor3rd Gear

40 12050 60 70 80 90 100 110

km/h

50

80

60

70

dB

(A)

Pa Full Load

50% Throttle0% Throttle

Comparison of NVH characteristics of

Electric and IC Engine driven vehicles

The Volt and Leaf have similar road and wind noise to traditional vehicles

Masking Noise

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Road Noise 50km/h Road Noise 80km/h Wind Noise 100km/h Wind Noise 140km/h

Nissan Leaf

Chevrolet Volt

IC Competitor

NVH Challenges of Alternative Powertrains

Comparison of NVH characteristics of Electric and ICEngine driven vehicles

Specific Challenges in Electric Vehicles

Integration refinement of an APU into the vehicle

Specific NVH Challenges

EV vehicles have a number of specific issues that require attention, for example:

• Auxiliary Devices

• Vacuum pumps for brake assist

• Battery contactor noise at key on/off

• Pedestrian Awareness

• Nissan Leaf exterior sound source

• Chevrolet Volt Active Warning

The Volt has a strong multi order characteristicfrom the vacuum pump

Vacuum Pump Noise

Vacuum Pump RunningVacuum Pump Off

Specific NVH Challenges

• The Nissan Leaf has significant noise from the batterycontactors at key on

• Nissan have created key on effects for the vehicle to helpminimise the disturbance from these noises

Contactor Noise

Key On Effect 1 OnKey On Effects Off

Specific NVH Challenges

• The Nissan Leaf includes an exterior sound source system toimprove safety for pedestrian, particularly the blind and partiallysighted

• The majority of the additional energy is added between 200 and1000Hz with a swept tone up to 2300Hz

PedestrianAwareness

Exterior Sound Source OnExterior Sound Source Off

Specific NVH Challenges

• The Volt does not have an ‘alwayson’ exterior sound source fitted

• However an additional warningmechanism is included - when theheadlight main beam is flashedthe vehicle horn is cycled rapidlyto provide a less intimidatingwarning than the main horn

• This warning is effective whilstbeing less aggressive to road usersnot isolated from the horn by avehicle body

PedestrianAwareness

Specific NVH Challenges

NVH Challenges of Alternative Powertrains

Comparison of NVH characteristics of Electric and ICEngine driven vehicles

Specific Challenges in Electric Vehicles

Integration refinement of an APU into the vehicle

Integration refinement of an APU

into the vehicle

ICE Generator Ring

Sun

CarrierIntermediate

shaft

WHEEL

Diff

TractionMotor

Planetary Gearset

Powertrain Layout of the Chevrolet Volt

0 10010 20 30 40 50 60 70 80 90

km/h

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rpm

• The plot below shows how APU speed in range extended mode is a function of powerdemand

• The APU appears to be run at or near full load in all conditions with the speed beingaltered according to the power demand

• This causes an odd subjective feel during over run conditions, with the APU labouringwhilst the vehicle slows down

APU Speed vs. Road Speed

Integration refinement of an APU

into the vehicle

100% Throttle50% Throttle0% Throttle(Run Down)

3 124 5 6 7 8 9 10 11

s

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• The start up of the APU in the Volt is very well managed, imperceptible in normal drivingconditions

• The use of the second motor/generator unit allows the IC engine to be spun up to operatingspeed before it is fired, eliminating the kick usually experienced in IC only vehicles

• A similar strategy has been employed on shut down

APU Start Up

Integration refinement of an APU

into the vehicle

Road SpeedAPU rpmPT Vertical VibrationDrivers Seat Rail Vertical Vibration

Thermal Benchmarking of the

Nissan Leaf and Chevrolet Volt

David Bridge – MIRA Ltd

Tests Conducted

• Benchmarking covered

> Body Leakage

> Installed Airflows

> HMI

> Subjective Appraisals

> Climatic Wind Tunnel Tests

CWT Testing

• Power performance

> WOT throttle tests

• Cooling system related

> Gradient climbs

> City drive cycles

> Vmax

• HVAC related

> AC system performance

> Heater system performance

> Screen (defrost) clearing

LC Vehicle Testing Challenges

• Electric AC compressors & PTC heaters

• Independent cooling circuits

• Battery regeneration post test

• Battery temperature vs test time

• Heater performance test (1500rpm)

• Pre-conditioning

• PWM pumps and fans

• Auto vs ‘manual’ HVAC settings

• Amount of instrumentation (Volt)

Volt Coolant Circuits

Volt Coolant Circuits

WOT Test

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Dyn

oFo

rce

-N

Speed - mph

Leaf vs Volt: Force at WOT

Leaf

Volt - Battery Only

Volt - Battery and Engine

Engine On

Dyno Limit

WOT Test

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Speed - mph

Leaf vs Volt: Developed Power at WOT

Leaf

Volt - Battery Only

Volt - Battery and Engine

Engine On

Body Leakage

Body Leakage

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Air

Flo

w-

l/s

Pressure Drop - Pa

Leaf vs Volt Cabin Pressure Drop Characteristics

Leaf

Volt

Body LeakageLeaf: 43.6 cm2

Volt: 29.0 cm2

Installed Flows: Face Vents

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Air

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Blower Setting (%)

Leaf vs Volt Face Vent Characteristics

Leaf

Volt

Installed Flows: Floor Vents

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Leaf vs Volt Floor (Hot) Vent Characteristics

Leaf

Volt

Installed Flows: Defrost Vents

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Air

Flo

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l/s

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Leaf vs Volt Defrost (Hot) Vent Characteristics

Leaf

Volt

HMI - Leaf

HMI - Volt

CWT Testing

• 45°C AC Pull Down

• 45°C Mumbai city drive

• 45°C Vmax and idle

• 49, 38, 25, -5°C EUCD drive cycles

• 45 & 25°C max acceleration cycles

• GL40 – 12% Gradient at 40kph (30°C) - GG

• GL100 – 7% at 100kph – (38°C) – DD

• GL60 – 8% at 60 kph (38°C)

• -20°C heater warm-up

• -8°C screen defrost

• WOT tests

CWT Testing

AC Pull-Down

• Vehicle soaked to 45°C

• Volt plugged in overnight but charger failed after 16miles

• Solar load at 1000W/m2 for 4 hours

• 60 kph 40 minutes

• 80 kph 30 minutes

• Static 20 minutes

• HVAC

> Full fans

> Full cold

> Face mode

> Recirculation

AC Pull-Down

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Tem

pe

ratu

re-

°C

Time - Minutes

Av Interior Temperatures - 45°C AC Pull-Down (Volt vs Leaf)

Average Interior (GM Volt)

Average Interior (Nissan Leaf)

AC Pull-Down

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ne

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ed

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Av Interior Temperatures - 45°C AC Pull-Down (Volt vs Leaf)

Average Interior (GM Volt)

Average Interior (Nissan Leaf)

Engine Speed

AC Pull-Down

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Tem

pe

ratu

re-

°C

Time - Minutes

Av Face Vent Outlet Temperatures - 45°C AC Pull-Down (Volt vs Leaf)

Average Face Vents (GM Volt)

Average Face Vents (Nissan Leaf)

Heater Warm-Up

• Vehicle soaked to -20°C

• Volt plugged in overnight

• 50 kph 60 minutes

• 100 kph 30 minutes

• Static 20 minutes

• HVAC

> Full fans

> Full hot

> Foot vents

> Fresh air

Heater Warm-Up

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-10

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10

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30

40

50

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Tem

pe

ratu

re-

°C

Time - Minutes

Average Interior - -20°C Heater Warm-Up (Volt vs Leaf)

Average Interior (GM Volt)

Average Interior (Nissan Leaf)

Heater Warm-Up

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-10

0

10

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30

40

50

60

70

0 10 20 30 40 50 60 70 80 90 100 110 120 130

Tem

pe

ratu

re-

°C

Time - Minutes

Floor Outlet Temperatures - -20°C Heater Warm-Up (Volt vs Leaf)

LHS Floor Outlet (GM Volt)

RHS Floor Outlet (GM Volt)

LHS Floor Outlet (Nissan Leaf)

RHS Floor Outlet (Nissan Leaf)

Heater Warm-Up

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3500

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-10

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Spe

ed

-rp

m

Tem

pe

ratu

re-

°C

Time - Minutes

Floor Outlet Temperatures - -20°C Heater Warm-Up (Volt vs Leaf)

LHS Floor Outlet (GM Volt)

RHS Floor Outlet (GM Volt)

LHS Floor Outlet (Nissan Leaf)

RHS Floor Outlet (Nissan Leaf)

Engine Speed

Conclusions

• Testing of EV and HEV type vehicles offers uniquechallenges

• Both vehicles communicate to user impact of HVACchoice on energy use

• Close attention to sealing of body and FEM on Volt

• Leaf delivers more installed airflows

• AC performance similar

• Cabin warm-up for Leaf is very poor

• Cabin warm-up for Volt much better (temp) butdepends on engine switching and is subjectively poor