- Porsche Engineering

- Porsche Engineering
Porsche Engineering
Magazine
Macan Models: Fuel consumption (combined) 9.2 – 6.1 l/100 km; C02 emissions (combined) 216 – 159 g/km; Efficiency class: E–B
CUSTOMERS & MARKETS Records on the circular track at Nardò
PORSCHE UP CLOSE Battery development for the Porsche 919 Hybrid
ENGINEERING INSIGHTS High-voltage testing from the cell to the battery
ISSUE 2 / 2014
www.porsche-engineering.com
Intelligent
Thermal Management
Insight into new solutions
It’s nice to see
great ideas gain ground.
Dear Readers,
_____ We would like to welcome you to this issue with
a friendly “ni hao.” Our new location in Shanghai will
shortly be opening its doors. For over 20 years, we’ve been
devoting ourselves to the specific requirements of our Chinese customers. Thus, the foundation of this subsidiary is
the logical consequence of our two decades of involvement
in China—a tradition-infused step into the future.
The focus of this issue—thermal management—has a number of parallels with this: a traditional topic in the field
of vehicle development, but one which, with a view to
future-oriented mobility and alternative drive technologies,
is becoming ever more diverse and complex. More than
enough reason for us to take a closer look at this matter,
from function development to temperature management
for batteries, in the spirit of our commitment to forwardlooking and “intelligent thermal management.”
Malte Radmann and Dirk Lappe,
Managing Directors of Porsche Engineering
About Porsche Engineering
Creating forward-looking solutions was the standard
set by Ferdinand Porsche when he started his design
office in 1931. In doing so, he laid the foundation for
today’s engineering services by Porsche. We renew
our commitment to that example with each new project
that we carry out for our customers.
The scope of services provided by Porsche Engineering
ranges from the design of individual components
to the planning and execution of complete vehicle
developments, and is also transferred to other sectors
beyond the automotive industry.
One special highlight this year for Porsche was the return
to Le Mans. Vehicle development of the 919 Hybrid and
ultimately the spectacular race itself have been a major focus of this year. In our “Le Mans” article, we take another
look at the event and also report on the special challenges
that had to be mastered in the battery development process
for the 919 Hybrid.
You’ve learned about the special features of our testing
grounds in Nardò in previous issues of the magazine. Join
us this time for a spin on the circular track in “A Perfect
Ground for Records—Nardò,” as we take a look back at
the most fascinating records of recent years.
We hope you enjoy this issue
of the Porsche Engineering Magazine.
Sincerely,
Malte Radmann and Dirk Lappe
Editorial
Porsche Engineering MagazinE
3
26
Customers & Markets
Records in Nardò
History is written in Nardò. Again and again.
We take a look at some of the most exciting record
drives of recent years.
25.6 °C
18.2 °C
22.2 °C
12
22
STATE OF CHARGE
High
AMBIENT
TEMPERATURE
Low
High
Low
AMBIENT
TEMPERATURE
Low
17
32
inteLLiGent
tHermaL manaGement
12 efficient interaction
Holistic thermal management
for future needs
17 intelligent Functions
Function development for
cooling systems
22 optimal Battery temperature
management
New solutions for functionality
and range
38
Customers & markets
enGineerinG insiGHts
26 nardò
A perfect ground for records
38 keeping Current
Testing from the cell
to the battery
PorsCHe uP CLose
32 Le mans
Porsche returns to the
race track
03 Editorial
06 News
44 Imprint
36 919 Hybrid
Battery development
for Le Mans
maCan modeLs: Fuel consumption (combined)
9.2 – 6.1 l/100 km; C02 emissions (combined)
216 – 159 g/km; Efficiency class: E–B
Contents
Porsche engineering MAGAZINE
5
保时捷工程技术研发公司在华成立子公司
保时捷工程(Porsche Engineering)通过建立中国子公司
进一步拓展亚洲市场:保时捷工程技术研发(上海)有限公司
(Porsche Engineering Shanghai Co., Ltd)将于新旧年交替之
际正式挂牌成立。
继捷克布拉格和意大利纳尔多之后,上海将成为保时捷工
程在德国之外的第三个基地。随着各个子公司与总公司的专业
一体化的保证,客户可享受引领未来的汽车领域高端服务。在上
海,保时捷工程的工程师们将继续致力于发挥整车研发和系统
研发方面的核心实力。
保时捷工程投身于中国市场已有20逾年的历史。为中国客户
提供研发是保时捷工程的传统业务。
“我们在中国的客户特别
重视一体化的项目团队,以实现最优化的合作”,首席执行官雷
德民(Malte Radmann)说道,
“上海子公司可助我们在未来更
全面满足客户这一需求。”
与同济大学合作是保时捷工程在中国的重要战略之一。双
方已于今年6月签署合作协议,计划在培训、研究及工程技术领
域携手展开广泛的合作。以布拉格分公司与布拉格理工大学成
功的合作模式为典范,双方将在科学、研究、教学、试验台架和
实践方面密切交流。
Porsche Engineering Founds
Subsidiary in China
___ With the foundation of a subsidiary, Porsche Engineering
is expanding its traditionally strong engagement in Asia: The
Porsche Engineering (Shanghai) Co., Ltd. will open in China
with the beginning of the new year.
Besides Prague and Nardò, Shanghai will become the third
location outside of Germany. As a result of a perfect integration of the locations it is for sure that the customers always
receive holistic premium engineering services for future-oriented
mobility. In Shanghai, the Porsche engineers will concentrate
on proven core competencies of overall vehicle development
and system development.
News
Porsche has a strong tradition of working with Chinese customers—engineering services have been offered in China for
over 20 years. “Our customers in China place great importance
on integrated project teams for best cooperation,” says CEO
Malte Radmann, “and with our new location in Shanghai,
we’ll be able to fulfill that demand even better in the future.”
One important component of the engagement in China is the
collaboration with Tongji University in Shanghai. A collaboration agreement was signed in June of this year for a wideranging cooperation. Based on the example of the successful
cooperation between the Prague location and the technical
university there, the collaboration in Shanghai will also strive
for a fruitful exchange in terms of science, research, teaching,
testing facilities and practical experience. n
develoPmenT cenTer
eXPanded
greenTec aWards
PresenTaTion
Work-liFe balance aT
Porsche engineering
___ With the putting into operation of
the new design studio together with a
conception building, the aero-acoustic
wind tunnel and the electronics integration center, on July 18, 2014, the
completion of an important step in the
expansion of the Weissach Development Center was concluded. By 2016,
a new powertrain testing building with
18 test benches will be built for the development of new hybrid drives as well
as new combustion engines and electric
motors. Engineering services for external customers will also profit from these
new high-tech facilities. With these investments, Porsche is further expanding its core competencies and creating
new resources not only for its own
developments; through the symbiotic
connection between sports car series
development and engineering services,
these resources will also be available for
external projects. n
___ At this year’s awards ceremony for
the GreenTec Awards—Europe’s biggest
environmental and business award—
Malte Radmann, CEO of the Porsche
Engineering Group GmbH delivered
the speech in honor of the winner in
the automobility category. The victor
was the RUBIN project, a collaboration
between the tire manufacturer Continental and the Fraunhofer Institute for
Molecular Biology and Applied Ecology.
The aim of the project is to further develop the yield of natural rubber from
Russian dandelion plants and also its
cultivation for industrial use. The prizes have been awarded for outstanding
environmental engagement and green
technology since 2008. This year the
award was presented for the first time
in cooperation with Messe München as
the opening event of the world’s largest
environmental trade fair—the IFAT. n
___ The success of any company is
based on motivated and capable employees, and a good work-life balance
is a fundamental factor in promoting
that. Porsche Engineering offers flexible, individualized work models to
enable employees to successfully balance their family, free-time and working lives. And it’s not only employees
who benefit—students receive optimal
support as well. One current example
of this is the professional athlete Jonathan Scholz, handball player for the
first-league club SG BBM Bietigheim.
The mechanical engineering student
has been with Porsche Engineering as
an intern in the engine design department since the beginning of September.
A flexible working schedule enables him
to combine the regular training activities that a professional sports career requires with important practical experience for his studies. n
8
Porsche engineering MagazinE
neWs
News
prizes for “Driving
Technologies” Image Film
Porsche Strengthens
its Presence in Nardò
___ The new Porsche Engineering corporate film “Driving Technologies” has
been honored with two international
film prizes: It received a Gold Award
at the Communicator Awards in New
York and a Silver Victoria from the
Internationale Wirtschaftsfilmtage in
Vienna. The film shows the company
as an innovative engineering services
provider for future-oriented mobility.
The film focuses in particular on the employees and their engineering expertise.
What makes the film special is its trailerlike effect that has been unprecedented
in the world of corporate videos. n
___ In a visit to Stuttgart-Zuffenhausen
by Nichi Vendola and Angela Barbanente—president and vice president of
the southern Italian region of Apulia,
Porsche and the Apulian political leaders
jointly reaffirmed their partnership for
the strategic development of the Nardò
Technical Center and the region of Apulia. “The Nardò Technical Center with
its rich array of facilities has become
an integral part of the holistic Porsche
engineering services and the Porsche
concern itself,” said Matthias Müller,
Chairman of the Executive Board of
Dr. Ing. h. c. F. Porsche AG. Porsche
plans large-scale investments in the
proving ground. Nichi Vendola emphasized that Porsche and the Nardò Technical Center are important partners for
the region: “With Porsche we will continue to develop our region in a positive
direction in terms of economic strength,
jobs and infrastructure.” n
Weblinks
www.porsche-engineering.com
www.youtube.com/
watch?v=nJL9v8KXmmo
NEWS
Porsche Engineering Magazine
9
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10
Porsche Engineering Magazine
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INTELLIGENT THERMAL MANAGEMENT
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Intelligent
Thermal
Management
0°
10°
20°
30°
____ Thermal management ensures that temperatures in the vehicle are maintained
within an optimum range. Mastering the challenge involves an extensive range of tasks
and applications requiring intelligent solutions. Yet thermal management is about
much more than keeping a cool head. One goal, for instance, is to direct heat flows in
a way that reduces fuel consumption while improving interior comfort. An essential
challenge in creating forward-looking mobility.
Within this broad subject, there are various sub-areas that come into play—thus on
the following pages we describe the efficient interplay between component protection,
comfort and emissions reduction. Two other vital aspects are also discussed: function
development and battery temperature management.
INTELLIGENT THERMAL MANAGEMENT
Porsche Engineering Magazine
11
THERMAL MANAGEMENT
– 30°
– 20°
– 10°
0°
10°
20°
Efficient
Interaction
____ The increasing electrification of the powertrain has given rise to new challenges
in many areas of vehicle development. In the last edition, we took a brief look at
the significance of thermal management in the area of electric motors and we would
now like to explore this interesting topic in more detail.
By Björn Pehnert
Photos by Jörg Eberl
An essential part of the development of every vehicle: testing in a climatic wind tunnel
12
Porsche Engineering Magazine
INTELLIGENT THERMAL MANAGEMENT
30°
Macan Models: Fuel consumption (combined)
9.2 – 6.1 l/100 km; C02 emissions (combined)
216 – 159 g/km; Efficiency class: E–B
Simulation of extreme
conditions in a climatic
wind tunnel
Thermal management
The field of thermal management
originally arose from the need to protect components, in particular the engine,
transmission, and all other parts in the
engine compartment. Modern thermal
management now has three core areas,
two of which are relatively new: improving comfort and reducing emissions.
These individual areas will be discussed
in detail on the following pages.
coolant radiator is insufficient and further coolers have to be used.
Several thousand liters of air per second are required to discharge these high
capacities to the environment via the
cooler. A large part of the overall engine heat does not flow into the coolant,
but is discharged into the atmosphere by
means of convection.
The potential heating of the engine
compartment due to this mechanism
is a further focus of component pro-
tection—heat protection. If the engine
compartment is overheated, components such as engine control units, spark
coils or plugs can exceed their threshold
temperatures. Reflectors, air vents, and
active ventilation from the subfloor or
hood are used to counteract these high
temperatures.
Even if threshold temperatures are not
exceeded, lowering the temperature can
be sensible, for example to ensure that
components can be operated more efficiently. ›
Component protection
Nearly every component in a vehicle
has a threshold temperature range in
which it can operate. Keeping within
this range is the focus of the component protection aspect of thermal management. An example of this is the
engine, which must not be operated in
temperature ranges in which cavitation
(the formation and disintegration of
steam-filled cavities in liquids), knocking, or thermo-mechanical stress can
cause damage or result in a breakdown.
This means that heat currents of up to
100 kW might have to be discharged.
Above a certain waste heat level one
Preparing a cooler on a test bench
INTELLIGENT THERMAL MANAGEMENT
Porsche Engineering Magazine
13
Comfort—warm feet and a cool head
oRIGINAL
HEAT-PRoTEcTEd
The second core area of thermal management is improving the comfort, illustrated here by the appropriate air conditioning of the vehicle cabin. Modern
combustion engines and particularly
hybrid and electric vehicles produce so
little heat at low loads that sufficient
interior heating is no longer possible
with conventional methods. Though, in
order to provide the necessary levels of
comfort in the cabin, additional heating units are used to compensate for the
heat deficit.
Temperature (C)
Representation of a simulated temperature reduction at a generator
with intelligent heat protection measures
The figure above shows the result of
heat protection measures for a generator. A two-component heat protection
plate has considerably reduced the heat
exerted on the generator by the exhaust
system. The generator temperature has
been considerably decreased, with the
result that efficiency could be raised
from 70 percent to 90 percent. As the
thermally protected generator now had
a considerably higher output, it could
be replaced by a smaller, lighter, and
cheaper component.
Ensuring component protection has long
been an established part of the series development of conventional vehicles. One
area where new challenges and special
requirements are arising is the thermal
management of (hybrid) electric vehicles.
New heat-conducting materials and
cooling concepts are being used to ensure component protection in vehicles
with alternative drive systems. Graphite, heat pipes, and vapor chambers are
approaches currently being developed
to make the best use of hybrid components and to protect them against
undercooling and overheating. In particular, maintaining the optimum tem-
14
Porsche Engineering MagazinE
perature for batteries has proven to be
very complex, as the different output
requirements and cell types require different approaches. The article “Optimal Battery Temperature Management”
(page 22) provides a deeper insight into
the design of such systems.
One technological component in this
area that is gaining in importance is
the heat pump that applies energy to
transfer low temperatures to higher
heat levels. When the heat transfer runs
from high levels to a low temperature
level, the term used is air conditioning.
The heat pump or air conditioning system can be driven thermally, thermoelectrically, or by a compressor. As an
alternative to using a heat pump as an
Thermo-acoustic
generator
Heat pump
High temperature
Low temperature
Stack
Heat transfer unit
Ambient
temperature
Resonator
Stack
gas
Functional principle of a thermo-acoustic cooling system
INTELLIGENT THERMAL MANAGEMENT
Ambient
temperature
Functions
MODEL
TEST BENCH
VALIDATION
1D SIMULATION
VALIDATION
code
CONTROL UNIT
APPLICATION
Functional development process sequence in thermal management
additional heating unit, PTC heaters can
be used that provide warmth in a highly
dynamic way.
The rising number of technologically
different devices makes it increasingly
more complex to find the optimum concept for one particular vehicle. To be
able to compare various cooling concepts quickly and meaningfully, Porsche
Engineering has developed several simulation and calculation tools.
Compressor-driven cooling systems
are used in conventional cabin air conditioning. In this case a hermetically
sealed circuit compresses a gaseous medium with a compressor. This is liquefied in the downstream condenser and
the compressed hot coolant gives off
its heat into the atmosphere. The heat
can be given off into the air at the front
end of the vehicle or alternatively into a
cooling circuit integrated in the overall
vehicle cooling system. The liquid coolant is fed to a vaporizer via a throttle,
turning from liquid to gas and thereby
acquiring heat. The warmer cabin air is
fed into the vaporizer and cooled, creating a pleasant climate in the vehicle
interior at high ambient temperatures.
In winter, this process can be reversed
so that the air conditioning system can
now be used for heating and thereby
functions as a heat pump.
The refrigerant R134a is largely used in
passenger car air conditioning systems,
which in coming years will be replaced
by more environmentally friendly alternatives. In addition to R1234yf, natural
coolants such as carbon dioxide (CO2),
referred to as R744 by specialists in the
field, will be used. The alternative coolant CO2 requires especially innovative
solutions to be capable of creating efficient cooling / heating circuits for passengers and components.
INTELLIGENT THERMAL MANAGEMENT
The thermal dynamics experts at
Porsche Engineering have even more
innovative solutions in their repertoire.
An interesting example of this is the
thermo-acoustic air conditioning system (see illustration on the left page).
Here, thermal energy from the engine
is used to start oscillations in a resonator. These oscillations are used to drive
a cooling system. For this to function,
in addition to the resonator, so-called
stacks are required. Stacks are components that can convert thermal energy
into oscillations and vice versa. A stack
(driver) generates a pressure gradient
via an externally created temperature
gradient and thereby an acoustic impulse in the resonator. The excitation
created is then converted into a temperature gradient by the second stack
(generator stack) so that the hot and
cold sides that arise here can be used
as a heat pump. This alternative has no
moving parts and has the advan-
›
Porsche Engineering Magazine
15
tage that it only requires engine heat to
operate.
mance while taking the engine geometry,
number of cylinders and other parameters into account.
performance of a thermal management
system integrated in a vehicle.
Emissions reduction
The constant further development of
the combustion engine and continuously falling emission and consumption
values means the demands on thermal
management are increasing. Downsizing sees the use of supercharged engines
that have a high specific output, a wide
revving range with maximum torque,
and good transient response characteristics. However, the exhaust gas turbocharging required for this results in
greater levels of residual gas content
and higher temperatures and pressures
in the combustion chamber that in turn
result in an increased tendency towards
knocking in the engine. Later ignition
is required to prevent knocking. This
means a later combustion center of
gravity and therefore a lower engine
efficiency level.
Complete package
thermal management
In addition to the fields of component
protection and comfort, modern thermal
management is also playing an increasingly important role in reducing CO2
emissions for example. The familiar engine thermostat alone is no longer sufficient for the thermal management of
modern engines. While heating up, every
degree more of engine temperature can
contribute to reducing emissions.
To be able to efficiently use the waste
heat generated by the engine, standing
water, integrated exhaust manifolds, and
split cooling are used. So that useful engine heat is not lost into the atmosphere,
engine encapsulation and the correct
choice of cooling system dimensioning
must be given exact consideration. Optimum valve control also plays an important role here as it contributes to minimizing CO2 emissions and waste heat.
The effective cooling system size can be
influenced by valves such as thermostats
or proportional valves. To increase the
dynamic response of the cooling system
for example, its size is scaled down, by
disconnecting thermal ballast such as
compensating reservoirs, air extraction
ducts or non-required plate heat exchangers via the controller.
One basic task of thermal management
not yet discussed is the determination
of the heat energy transferred to the
coolant. In conjunction with the analysis of real engine heat balances on the
test bench, simulations are used to
design the cooling system in the first
development phases. Porsche Engineering uses its own developed software for
this. This determines the relationship
between heat being transferred to the
coolant and effective engine perfor-
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Porsche Engineering Magazine
To counteract this effect, Porsche Engineering is examining the possibilities
of reducing intake temperatures. Cooler
intake air reduces the likelihood of
knocking as well as the exhaust temperature, thereby increasing efficiency
and reducing CO2 output. Measures
such as more efficient charge air coolers
and using super cooling or refrigerant
cooling are being investigated with the
aim of reducing intake temperatures.
Emissions cannot only be reduced by
components and parts; intelligent functions in the vehicle also have a role to
play (see article "Intelligent Functions").
It is important that the many components in a vehicle cooling system are
doing the right thing at the right time.
This is the only way to achieve good
overall levels of efficiency and performance. Here it is also necessary that
new functions are developed and applied in vehicle management systems.
Only a combination of software and
hardware can obtain the maximum
INTELLIGENT THERMAL MANAGEMENT
Today’s thermal management with its
three major fields of component protection, comfort, and emissions reduction
takes on an important superdisciplinary
function in the overall vehicle. Conventional cooling concepts are increasingly
being stretched to their limits and innovative approaches are gaining in
importance. The increasing complexity requires a better understanding and
a greater degree of integration of the
fields involved. n
Thermomanagement
– 30°
– 20°
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0°
10°
20°
30°
Intelligente
Funktionen
____ Für ein aktives Thermomanagement in Fahrzeugen ist die Funktionsentwicklung für
Kühlsysteme eine Grundvoraussetzung. In diesem Artikel erfahren Sie, wie genau diese
beiden Themen zusammenhängen und wie Porsche Engineering das optimale Zusammenspiel
im Entwicklungsprozess und in der Anwendung sicherstellt.
Text: Thomas Warbeck
Ein leistungsfähiges und effizientes
Thermomanagement in Fahrzeugen
erfordert nicht nur eine sorgfältige Auslegung von Kühlkreisläufen, sondern
auch eine intelligente Steuerung der im
Kreislauf verbauten Teile. Hierbei wird
stets eine bedarfsgerechte Kühlung angestrebt, was bedeutet, dass jede Komponente wie zum Beispiel Verbrennungsmotor, Batterie oder E-Maschine im
optimalen Betriebstemperaturbereich
liegt und im Kühlsystem verbaute Lüfter
und Pumpen nicht unnötig in Betrieb
sind. Dadurch wird eine höhere Reichweite sowohl von brennstoffgetriebenen
als auch von Elektrofahrzeugen ermöglicht. So werden beispielsweise Kühlerlüfter an kalten Tagen im Winter erst bei
höheren Kühlwassertemperaturen zugeschaltet als im Sommer, wenn selbst
nach Abstellen des Fahrzeugs für kurze
Zeit oft noch Kühl­bedarf besteht, um
eine lokale Über­hitzung von Kühlmitteln und Bauteilen zu vermeiden.
Intelligentes Thermomanagement
Solche Funktionen müssen im Entwicklungsprozess erarbeitet und schließlich
im Motorsteuergerät hinterlegt werden.
Besonders bei Prototypensteuergeräten
erweist es sich als vorteilhaft, wenn sie
schnell an neue Anforderungen und
Messdaten angepasst werden können
und mit der eigentlichen Entwicklung
des Kühlkreislaufs einhergehen.
Von den Anfängen der Wasserkühlung
zu schaltbaren Kühlkreisläufen mit
Kennfeldthermostat
Die einfachste und älteste Art der Motorwasserkühlung ist die Thermosiphonkühlung. Hier wird Wasser nur aufgrund
der Dichteunterschiede von warmem
und kaltem Wasser in Motor und Kühler
umgewälzt. Nachdem warmes Kühlwasser vom Motor in den Kühler gelangt ist,
wird es abgekühlt, sinkt nach unten und
wird von dort dem Motor wieder
›
Porsche Engineering Magazin
17
kühlbedarf
nein
hoch
hoch
ja
zelltemperatur
niedrig
umwälzen
zum kühlen
hoch
ladezustand
hoch
umgebungs temperatur
niedrig
zelltemperatur
niedrig
umwälzen
zum kühlen
hoch
hoch
niedrig
zelltemperatur
niedrig
umwälzen
zum kühlen
hoch
umgebungs temperatur
niedrig
zelltemperatur
niedrig
umwälzen
zum kühlen
Schematische Darstellung einer Batteriekühllogik als Basis für die Funktionsentwicklung
zugeführt. Durch Hinzufügen eines mechanisch angetriebenen Kühlerlüfters
konnte Anfang des 20. Jahrhunderts die
Effizienz gesteigert werden, auch wenn
eine Regelung zu diesem Zeitpunkt noch
nicht möglich war.
Der Einsatz einer Wasserpumpe verbesserte die Umwälzung, was zu höheren
Kühlleistungen führte. Um eine schnellere Aufheizung des Motors nach dem
Kaltstart zu ermöglichen, wurde in den
Kreislauf schließlich ein Thermostatventil eingesetzt, wodurch das Kühlwasser
temperaturabhängig über die Kühler
oder an ihnen vorbeigeleitet werden
konnte. Somit hatte das erste regelnde
Element Einzug in den Kühlkreislauf
gefunden.
Stellglieder in Kühlkreisläufen
Während sich einfache Thermostate bei
Erreichen der Betriebstemperatur öffnen und dem Kühlwasser den Weg zu
den Kühlern freigeben, lassen sich moderne Varianten so ansteuern, dass die
18
Porsche Engineering Magazin
Öffnungstemperatur des Thermostatventils zum Beispiel in Abhängigkeit
von der Motorlast angepasst werden
kann. Anfänglich wurde ein Lüfter mechanisch an den Motor gekoppelt und
lief somit bei niedrigen Drehzahlen im
Stand langsam und im Fahrzustand mit
großem Kühlluftmassenstrom entsprechend schnell. Heute ist eine elektrische
Ansteuerung möglich, die ein umgekehrtes Verhalten erzeugt.
In Fahrzeugen mit Verbrennungsmotor
werden mechanisch drehzahlabhängi­ge Wasserpumpen derzeit noch standardmäßig verbaut, jedoch sind elektrische
und damit flexibel regelbare Wasserpumpen in Serienanwendungen immer häufiger vorzufinden. Hinzu kommen je nach
Anwendung verschiedene Ventile, die
zum Beispiel die Innenraumheizung vom
Kreislauf zu- oder abschalten können.
Mehr als nur ein Kühlkreislauf
In modernen Fahrzeugen wie zum Beispiel Hybriden ist ein einzelner Kreislauf
Intelligentes Thermomanagement
aufgrund der Vielzahl an unterschiedlich
zu temperierenden Komponenten längst
nicht mehr ausreichend. Das Kühlwasser im Verbrennungsmotor kann nicht
zur Temperierung von Batterien benutzt
werden, da deren Betriebstemperatur
in der Regel weitaus niedriger ist. Die
Abstimmung und der Wärmeaustausch
zwischen den Kühlkreisläufen sind
ebenfalls wichtige Teile des Thermomanagements, für die Kühlstrategien entwickelt und in Steuergeräte­funktionen
umgesetzt werden.
Stetig steigende Nachfrage nach
angepassten Funktionen
Insbesondere aufgrund der immer strenger werdenden EU-Vorgaben hinsichtlich des CO2-Ausstoßes und anderen
Emissionen wird eine intelligente Steuerung des Kühlsystems immer wichtiger.
Für den Kunden sind darüber hinaus im
Falle verschiedener hinterlegter Modi
ein verminderter Verbrauch, gesteigerter Komfort oder auch herausragende
Performance direkt spürbare Vorteile.
kühlung aus
kühlmodus 1
kühlmodus 2
kühlmodus 3
kühlmodus 4
Funktionsentwicklung als Prozess,
Entwicklung von funktionellen
Kühlkreisläufen
Die grundlegenden Funktionen im
Kühlsystem werden bereits während
der Auslegung des Kühlkreislaufes
bestimmt. Verbaute Aktuatoren und
Schnittstellen zwischen verschiedenen
Kreisläufen geben einen gewissen Spielraum vor. Es stellt sich die Frage, anhand welcher gemessenen Werte von
Temperaturen, Drücken oder auch vorgenommenen Einstellungen durch den
Endkunden welche Aktuatoren verstellt
werden sollen.
Zunächst werden die zu verwendenden
Eingangsgrößen festgelegt und somit
bestimmt, auf welche Parameter das
Kühlsystem reagieren soll. Solche Eingangsgrößen können beispielsweise die
Kühlwassertemperatur oder die Umgebungstemperatur sein, aber auch Drehzahl und Last des Verbrennungsmotors.
Im Batteriekühlkreislauf ist darüber hinaus auch der Ladezustand zu berücksichtigen, da die von den Zellen abgegebene
Verlustleistung und damit der Kühlbedarf hiervon abhängig sind. Auch für
eine elektrisch angeschlossene Batterieheizung ist diese Größe interessant.
Die Ausgangssignale sind überwiegend
durch die verbauten Aktuatoren vorgegeben, jedoch können auch weitere
Signale ausgegeben werden, die an
anderen Stellen der Motorsteuergerätsoftware Verwendung finden. Dies kann
beispielsweise dann der Fall sein, wenn
die Anforderung zum Abschalten der
Klimaanlage ans Motorsteuergerät gesendet werden soll.
Nach Definition der Ein- und Ausgangssignale werden die eigentlichen Funktio­
nen beschrieben. In Abhängigkeit vom
Betriebsmodus, dem Ladezustand der
Batterie (SOC, engl. „state of charge“),
der maximalen Zelltemperatur und der
Umgebungstemperatur werden für jeweils unterschiedliche Kombinationen
andere Setups gewählt. Wichtig ist
ebenso die Definition von sinnvollen
Parametern, die während der Applikation
im Fahrzeug noch einfach geändert werden können. Grenzwerte für den Ladezustand, die Umgebungs- und maximale
Zelltemperatur sind Beispiele hierfür.
Modellierung in MATLAB / Simulink
Nach dem Entwurf müssen die gewünschten Funktionen mithilfe geeigneter Software modelliert werden. Bei
Porsche Engineering geschieht dies mittels MATLAB / Simulink. Die Modell-
Intelligentes Thermomanagement
und Simulationseinstellungen werden so
gewählt, dass das Programm schließlich
echtzeitfähig ist. Hierfür muss die Rechenzeit so kurz wie möglich gehalten
werden, damit sämtliche Rechenprozesse auf dem Steuergerät weniger Zeit
in Anspruch nehmen als das Zeitintervall, in dem die entsprechenden Messwerte übermittelt werden. Nur so lässt
sich sicherstellen, dass die Ausgangssig­
nale jeweils passend zu den entsprechenden gemessenen Eingangssignalen
berechnet werden können.
Das fertige Modell kann nun zunächst
in MATLAB / Simulink in einem ersten
Schritt getestet werden, indem Eingangsvariablen mit zeitlichem Verlauf
gezielt vorgegeben und die Ausgangswerte auf Plausibilität geprüft werden.
Hierbei spricht man von „Model in the
Loop“-Testing (MIL).
Virtueller Prototyp des Kühlsystems
Ein weitaus näher an der Realität liegender Modelltest kann mithilfe einer
gekoppelten Simulation stattfinden. In
vielen Projekten von Porsche Engineering werden während der Entwicklung
und Optimierung von Kühlkreisläufen
mit Prüfstands- und Fahrzeugmessdaten validierte 1D-Modelle erstellt. Diese
bilden die Physik des Fluids auf seinem
Weg durch Elemente wie Kühler, Leitungen, Pumpen und Ventile sehr genau
ab. Hierfür wird die Software GT-Suite
verwendet, welche sich mit MATLAB / Simulink koppeln lässt. ›
Porsche Engineering Magazin
19
temperatur
des kühlsystems
Ventilstellung 1
Ventilstellung 2
umgebungstemperatur
modell der
kühlsYstemsteuerung
lüfterdrehzahl 1
anzeIge der
bereChneten
grÖssen
lüfterdrehzahl 2
pumpendrehzahl 1
fahrgeschwindigkeit
pumpendrehzahl 2
klimaanlage aus
anforderung an lüfternachlauf
signalgenerator
Modellvalidierung des Kühlsystemfunktionsmodells mittels vordefi nierter Testszenarien
Der Einfluss der Kühlsystemsteuerung
auf das Verhalten des Fahrzeugs kann
somit direkt getestet werden, indem über
die modellierte Steuerung in MATLAB /
Simulink Parameterwerte wie zum Beispiel Ventilstellungen an GT-Suite übergeben werden. Das physikalische 1DModell wiederum übergibt Messwerte
wie Temperaturen zurück an MATLAB /
Simulink, die den dort modellierten
Funktionen als Eingangsgrößen dienen.
Der enorme Vorteil dieses Verfahrens
liegt darin, dass schon frühzeitig die
Kühlsystemfunktionen an die Physik
im Kühlsystem des Fahrzeugs angepasst werden können und bereits ein
erster sinnvoller Datenstand festgelegt
werden kann, bevor überhaupt mit
dem Fahrzeug gefahren wird. Da das
Kühlsystemmodell ständig aktualisiert
und auf den Fahrzeugstand abgestimmt
wird, kann die kostenintensive Testzeit
im Fahrzeug deutlich reduziert werden.
Das physikalische Modell fungiert gemeinsam mit dem Funktionsmodell als
virtueller Prototyp, mit dem schnell und
günstig gearbeitet werden kann.
20
Porsche engineering magazIn
Vom Modell zum Code
Nachdem das Modell in einem ersten
Schritt validiert wurde, steht die Umwandlung zur Software an. Somit wird
das Modell, das nur in MATLAB / Simulink lesbar ist, zu einem universell lesbaren Programmcode. Geschieht die Umwandlung mittels der dSPACE-Software
TargetLink, kann die Software analog
zum Modell direkt in der MATLAB /
Simulink-Umgebung getestet werden.
Hierbei handelt es sich um einen „Software in the Loop“-Test (SIL). Um die
Software schließlich aufs Steuergerät,
beispielsweise das Batteriemanagementsystem (BMS), übertragen zu können,
wird diese in Maschinencode übersetzt
und auf den Flash-Speicher des Geräts
übertragen.
Mit einem speziellen Testaufbau ist es
nun möglich, die Steuerung des Kühlsystems direkt an der später verwendeten Hardware zu testen. Über ein Hardware-Interface kann das Steuergerät
mit den entsprechenden Aktuatoren
und Sensoren verbunden werden, um
InTeLLIgenTeS ThermomanagemenT
dort über eine ETK-Schnittstelle verschiedene Programm- und Datenstände
direkt zu erproben. Zum einen kann somit die korrekte Ansteuerung und Bedatung der Aktuatoren und Sensoren
überprüft und zum anderen die Logik
der Kühlsystemsteuerung validiert werden. Eventuell auftretende Probleme
lassen sich so einfacher erkennen und
beheben als im aufgebauten Fahrzeug.
Es handelt sich hierbei um ein „Hardware in the Loop“-Testing (HIL).
Applikation im Prototyp,
Tests in Weissach und Nardò
Den nächsten Schritt in der Kette stellt
die Applikation dar. Durch Fahr-Erprobung im Prototyp werden das Systemverhalten untersucht und die Modellparameter angepasst. Idealerweise müssen
zu diesem Zeitpunkt nur noch kleinere
Anpassungen am Modell gemacht werden, sodass während der Fahrt mithilfe der INCA-Software von ETAS
vorrangig Änderungen in Kennlinien,
Grenzwerten und Fahrmodi direkt vor-
C = eingangsgrößen
–C–
funktIonsmodell
simulink-modell
kühlsYstemmodell
gt-suite-modell
Co-Simulation von Funktionsmodell und validiertem 1D-Kühlsystemmodell
genommen und bewertet werden können. Anstatt Parameter am PC oder
Prüfstand vorzugeben, werden zum
Bestimmen der Größen, unter anderem
Geschwindigkeit und Umgebungstemperatur, mehrere Fahrzyklen gefahren, beispielsweise auf dem PorschePrüfgelände im Entwicklungszentrum
Weissach oder auch auf den Strecken
des Nardò Technical Centers. Zusätzlich können für die optimale Applikation der Thermomanagementfunktionen
im Steuergerät Extrembedingungen
– warm und kalt – im Klima-Windkanal
simuliert werden.
im Fahrzeug zu garantieren, geht mit der
Entwicklung von Kühlsystemen die dazugehörige Funktionsentwicklung einher. Durch die Vernetzung dieser beiden
Aufgabenbereiche und die stetige Betrachtung aus der Gesamtfahrzeugperspektive erhält der Kunde erstklassige
Entwicklungsdienstleistungen. ■
Am Ende der Applikationsphase steht
ein finaler Stand von Programm und
Parameterdaten, womit das Thermomanagement auch in der Serie fähig ist,
erarbeitete Regelstrategien und Funktionen darzustellen.
Der Blick auf das gesamte Fahrzeug
Porsche Engineering hat stets das große
Ganze im Blick. Um die Funktionalität
Prüfgelände des Porsche-Entwicklungszentrums in Weissach
InTeLLIgenTeS ThermomanagemenT
Porsche engineering magazIn
21
THERMAL MANAGEMENT
– 30°
– 20°
– 10°
0°
10°
20°
30°
Optimal Battery
Temperature Management
____ Only an optimum temperature of the battery in electric and hybrid vehicles guarantees
the range targets and the desired functionality. We give you an insight into the three phases of the
special development of the storage battery.
By Manuel Groß
In spite of the still-limited range of
electric vehicles, driving performance requirements particularly for sports cars
are very high. Today’s lithium-ion cells
are capable of delivering the required
performance, but they also cause major
losses of multiple kilowatts. Dissipating that loss in the form of heat from
the battery system requires considerable
cooling capacity. The energy required
for cooling reduces the already low
range compared to conventional vehicles even further. The cooling system
must therefore be designed with maximum efficiency in mind. As already discussed in article “Efficient Interaction”
(from page 12 onwards), heating the
passenger compartment is also a problem: Unlike in a conventional combustion engine vehicle, at cold temperatures
there is not enough thermal energy in
the form of usable waste heat. The additional energy required for heating reduces the range of the vehicle even more.
Customer expectations with regard to
22
Porsche Engineering Magazine
the functionality, range and comfort of
conventional vehicles must ultimately be
met by battery-powered vehicles if they
are to succeed on the market. This requires new technical solutions to make
this a reality.
The optimum battery temperature
To manage the battery temperature, it
is necessary to know the optimal operating temperature of a battery cell. A
lithium-ion battery can be operated at
temperatures between approx. – 20 °C
and approx. +50 °C. Outside of these
limits, the cell chemistry can be affected
in ways that accelerate the aging (degradation) of the battery. Low temperatures, in particular, also lead to a rapid
increase in the internal resistance and
thus significantly limit the performance
of the battery. Lithium-ion batteries are
therefore often heated or at least thermally insulated to retard cooling.
INTELLIGENT THERMAL MANAGEMENT
The respective cell type must be taken
into account when determining the optimum battery temperature. Different
cell types have different cell chemistries
and geometric shapes, which must be
taken into account in the integration of
the battery in the cooling system from
the outset. Depending on whether direct cooling of the cells or an indirect
cooling plate solution is implemented,
the proper cooling medium must also
be chosen. The cooling media available
to the engineers at Porsche Engineering
include water / glycol, thermal oils, air,
and refrigerants.
Real or numeric—hand in hand
to a perfect product
For the determination and thermal description of specific factors and system
limits of the complex battery heat system, transient heat calculations and different material characteristics are taken
into account. Corresponding rough calculations can always be done manually
with the aid of simplified thermodynamics formulas.
Feasibility phase:
evaluating ideas
Since these basic equations are of limited usefulness, in thermal management
one makes use of special commercial
tools or tools developed by Porsche Engineering that utilize numeric approximation methods to create a sufficiently
precise representation of the transient
behavior of the battery. The different
simulation methods then make it possible to design new battery cooling systems and further optimize existing ones.
As in any project, the thermal management development process for batteries
begins with an idea that must first be
assessed in terms of its technical feasibility. In this first phase, a large number
of variants is simulated and information
processed to estimate the risks and potential of the idea. To quickly generate
meaningful information, Porsche Engineering has developed a thermal management tool. It is based on MATLAB /
Simulink and can be used for waste heat
calculations for the entire vehicle.
The tools used differ significantly in
their complexity and are used in a targeted manner depending on the project
state and depth. The following section
describes exemplarily the processes and
tools used in the three phases of battery
thermal management development.
To prevent overheating of the battery,
the generated waste heat must be dissipated. Based on the current and by
means of complex internal resistance
control maps, the waste heat can be determined by a driving cycle. The internal
resistance control maps, if not provided
Testing
0D
MaTLaB / Simulink
enertherm
Feasibility phase
Finding ideas
Concept phase
assessing concepts
1D
> Components
test
> Climate chamber
gT-Suite
3D
Design and development phase
> Cell testing
CCM+
implementation for series
production
> Model test
> Battery test
Complete vehicle
test
Series product
Example of the process of thermodynamic battery development
INTELLIGENT THERMAL MANAGEMENT
by the cell manufacturer, are recorded on
the cell level in the Porsche Engineering
cell test bench. This makes it possible
to determine how much waste heat is
produced. Since it is only sensible in rare
cases to dissipate the exact amount of
heat flow that the battery generates as
waste heat, it must be calculated how
much actually has to be discharged via
the cooling system.
Concept phase:
finding resilient solutions
Once the project has successfully passed
the feasibility phase, the next step is to
find concrete technical solutions and
compare them. Detailed questions with
regard to the right cooling medium, a
suitable cooling concept, and the thermal connection in the existing package
are now analyzed.
For every concept, a cooling performance analysis is carried out which can
be conducted in quasi 3D or 3D-CFD
(Computional Fluid Dynamics). This
analysis shows the potential of every
concept and must be able to convert
package restrictions, for example, into
viable thermal results. In some cases,
each individual cell has to be looked
at here. A suitable simulation model
would then have to represent a highly
complex thermal network of more than
500 cells.
To determine and evaluate the temperature homogeneity concerning the cell,
module, and battery levels, a tool such
as the GT-Suite is used. Depending on
the concept, a CFD calculation may
also be required in order to evaluate
the homogeneity caused by the fluids.
The STAR-CCM+ tool is used for this.
How good or realistic a simulation is
depends on the input. Cell, module,
and cooling trials are conducted in parallel with the simulation process and
close the gap between the virtual and ›
Porsche Engineering Magazine
23
Rth2
Rth1
Cell
1
Rth1
Cell
2
25.6 °C
18.2 °C
Rth1
22.2 °C
Rth3
R th = thermal resistance
Model (left) of the thermal network of an individual cell as the basis of a 1D overall battery simulation (right)
real worlds. At the end of the concept
phase, an optimal concept has been
determined which can now be handed
over to the detailed design and development phase.
Design and development phase:
the result is the product
Prototype batteries only become available relatively late in the project process.
The application as well as the driving
and operating strategy, however, have to
be developed earlier. For this, Porsche
Engineering uses self-developed thermoelectric battery models that can map
current-flow inhomogeneities as well as
voltage and temperature drifts on the individual cell level. The special feature of
these models is that they run in real time
and can therefore emulate the battery behavior for control units and other hybrid
components on the hybrid test bench.
24
Porsche Engineering Magazine
MATLAB / Simulink and in-house model
libraries are used as tools. 3D simulations can also be conducted during the
whole development process in order to
determine critical heat transmission coefficients, for example, and transfer them
to other models.
In 3D simulation, the focus can be on
temperature behavior as well as hydraulic features. CFD and solid models are
coupled to determine the transfer of
heat from the cell to the fluid. Validation measurements on the in-house test
bench ultimately enable correct implementation of key parameters in control
units and simulation models.
For transient calculations, 1D calculation with the GT-Suite is also suitable
—particularly for mapping the limit
temperatures and heating-up and cooldown times in dynamic driving cycles.
Parameter variations are especially easy
INTELLIGENT THERMAL MANAGEMENT
to conduct using this method. Material
thicknesses, tolerances, and material
characteristics can be varied and their
impact evaluated over a driving cycle.
One positive side-effect is the option
of coupling the battery model with the
cooling circuit model. In the context
of function development, these models
are of major importance for the development and virtual testing of software
based on a realistic scenario.
The key to success—thermal resistance
To precisely describe the behavior of
the battery under electrical loads and
simultaneous cooling, knowledge of the
thermal network of the overall battery
system is indispensable. This network
can usually be summarized in terms of
a thermal resistance. As a rule, thermal
resistance is composed of multiple thermal paths. These are comparable to a
Graphite
Cooling channel
Tcoolant
Graphite
R th transfer
R th cell
Tcell
CELL
PTC
CELL
R th graphite
PTC
T = temperature
R th transfer = thermal transfer resistance
R th graphite = thermal resistance graphite
R th cell = thermal resistance cell
PTC = positive temperature coefficient
Conversion of real structure into a thermal network model
parallel and serial resistance like in electrical applications. The graphic above
depicts a simplified thermal path using
the example of a battery with pouch
cells and integrated PTC heating.
The heat is directed from the pouch cell
towards the conductor—the electric
cell contact in this case—in a parallel
path via the graphite foils. The heat is
then conducted into the coolant via an
optimized cooling plate. To efficiently
move the waste heat from the cells to
the cooling plate, in the battery technology area Porsche Engineering uses new
materials such as graphite, phase transition materials and heat-pipes. These can
be used to achieve thermal conductivity
coefficients of over 1000 W / mK.
Unfortunately, good heat conductors
also conduct electricity well. Therefore
good electrical insulation is essential in
high-voltage batteries for vehicles. Re-
solving this conflict requires an ideal
compromise between thermal conductivity and high-voltage safety, which
makes the material selection process
considerably more difficult.
values of control unit functions to factors such as the ambient temperature.
This capability of pre-applying the
control units before real prototypes
are available significantly accelerates
the later final application in the complete vehicle.
Testing processes from the cell to
the battery: cross-sectional-function
Outlook
Characterizing the thermal network in
a complex simulation model requires
detailed thermal analysis on the test
bench. When the actually measured
data is compared with results from the
thermal network model, the differences
that emerge can be used to configure
the model parameters with great precision. This enables the successive development of a coordinated and validated
simulation model of the battery.
The future of thermal management for
batteries depends on developments in
cell chemistry. Lab research is currently
focusing intensively on lithium-air and
lithium-sulfur technology. Whichever
direction the developments may take,
thermal management will have to react
accordingly. This could lead to solutions that go beyond the automotive
technology used heretofore. n
This coordinated model now enables the
process of adapting limit and threshold
INTELLIGENT THERMAL MANAGEMENT
Porsche Engineering Magazine
25
A Perfect Ground for Records
Nardo
_____ Building a high-speed ring circuit with a length of 12.6 kilometers is no easy matter.
In 1975, Fiat turned this idea into reality. The track was intended to improve research and
development processes by testing cars under extreme conditions. As a result, the Nardò
circular track has become a site for numerous speed records. Over the years various vehicle
manufacturers have conducted test drives here and left their mark, breaking speed records
and writing history.
26
Porsche Engineering Magazine
Customers & Markets
1979
1979: The Mercedes- Benz C111- IV
hits 403 km / h
A long list of records
At the entrance of the Nardò Technical Center, which has been
managed by Porsche Engineering since 2012, a large board
lists the most significant records set on the track. It honors
special achievements and acts as a summary of 40 years of
record-breaking history. All these achievements have always
been conducted in private, far from spectators and prying eyes.
1979: The Mercedes-Benz C111-IV hits 403 km / h
911 Models: Fuel consumption (combined)
12.4 – 8.2 l/100 km; CO2 emissions (combined)
289 – 191 g/km; Efficiency class: G–F
The Italian record for the highest speed was attained in Nardò
by the Mercedes-Benz C 111-IV. On May 5, 1979 it reached
precisely 403.978 km/h thereby breaking the 400 km/h mark.
Behind the wheel was Hans Liebold, who was not a
race driver, but the chief project engineer, who completed the
flying lap of the circular Nardò track in 1 minute 57 seconds.
His car was built specifically with a twin turbo 4.82 liter
biturbo V8 engine producing 373 kW (500 hp) at 6,200 rpm.
The huge central fin and long tail of the vehicle were in stark
contrast with the otherwise rather narrow body. The appearance of this vehicle on the track was the culmination of a
­project launched in the late 1960s by the brand with the three›
pointed star.
Customers & Markets
Porsche Engineering Magazine
27
1982
the Porsche revolution
with the 928 s
1983
1982: The Porsche revolution with the 928 S
Both performance and endurance are aspects that the Nardò
ring track was specifically created for, while the focus was
always on reaching the highest speeds. Could the 928 S be as
successful as the legendary Porsche 911? This was a challenge
that Porsche set itself, as it veered away from the original DNA
of the brand itself, with a front engine/rear transaxle layout. As
innovative as the car appeared, however, the German engineers
had simply changed the formula, and the result was just as successful. On November 7, 1982, Porsche broke the 24-hour record with the 224 kW (300 hp) 4.7-liter V8, covering a distance
of 6,033 kilometers at an average speed of 251.4 kilometers
per hour.
1983: A Mercedes-Benz 190 E 2.3-16 flat out for 201 hours
After the Porsche record in 1982, Mercedes responded accordingly and from August 11 to 21, 1983 undertook a series of
record attempts with the 190 E 2.3-16: a race car, that later
dominated the DTM series and which had yet to be homologated for public roads. Over eleven days, the car set non-class
records as well as the 25,000 and 50,000 kilometer records.
28
Porsche Engineering Magazine
a Mercedes- Benz 190 E 2.3 -16
Flat out for 201 Hours
Everyone involved was enthralled for 201 hours, 39 minutes,
and 43 seconds. The special version of the sedan reached a top
speed of 250 kilometers per hour, made possible with a modified fuel injection system and by eliminating the power steering.
1994: Max Biaggi on the Violent Violet
While Nardò has always been a test track and has never
hosted a real race, there is nevertheless a feeling of unspoken
competition in the air, as every company strives for the best
performance. Max Biaggi broke the “flying kilometer” record
on June 4, 1994, in the saddle of the Violent Violet—a motorcycle built by Fabio Fazi: “It was an incredible experience,”
recalls the Roman rider. “All I could hear was the rushing
wind and the sound of the electric rotor; I felt like I was going to blast off at any moment. Lead acid batteries were installed instead of an engine. It had incredible torque and there
were no gears. You just pressed a button on the handlebars
and the bike shot off with a massive surge of power. At that
time such performance from electric engines was completely
unexpected.” Max Biaggi’s ride entered the Fédération Internationale de Motocyclisme (FIM) world records list with a
performance of 164.198 kilometers per hour.
Customers & Markets
1994
Bertone Z.E.R.
(Zero Emissions Record)
2000
1994: Bertone Z.E.R. (Zero Emissions Record)
The Bertone Z.E.R. (Zero Emissions Record) was a cigarshaped electric vehicle created to challenge the Americans on
the Bonneville Salt Flats in Utah. The idea was the brainchild
of Oscar De Vita, an engineering student at Milan Polytechnic.
“The vehicle was shaped like a rocket and was only as wide as
my shoulders,” recalls De Vita. “I submitted this project—the
thesis for my degree—to Mr. Bertone. He then decided to support and to push my project. The required wind tunnel studies
were done in eight months, while I worked on the electric motor.” The project was also sponsored by the battery producer
Fiamm, which wanted to promote lead acid batteries. “Instead
of going to America for the tests, we decided to take the car
to Nardò in order to try to beat the one-hour distance record
there. The goal was to reach 200 kilometers per hour with an
electric motor. Our result of 199.882 kilometers per hour was
very close. There was a slight drop in battery voltage towards
the end of the run so we didn’t quite manage to reach
200 km/h. If we had had nickel cadmium batteries, we would
have crossed the 200 km/h speed barrier.” This was just a first
taste, however: “We developed the project even further in
1995 for an attempt on the flying kilometer record at the
Nardò track. Bertone presented the new project at the Ge-
Pirelli beats the flying kilometer
record with Suzuki
neva Motor Show.” Former rally champion Sandro Munari
turned the drive down, as he feared the risk of overturning
under the centrifugal forces of the circular Nardò circuit. So
Oscar de Vita decided to drive himself. “I drove the car flat
out in the fourth lane, the one with the steepest bank, but at
first we could not get above 295 kilometers per hour.” However success was not far away. At the end of the test, de Vita
reported via his helmet microphone: “I’m past 300 km/h!”
The timekeepers then officially confirmed the new record of
303.977 km/h.
2000: Pirelli beats the flying kilometer record with Suzuki
Salvo Pennisi, Pirelli motorcycle product development manager and motorcyclist himself, has achieved 23 speed records
in Nardò. “Nardò,” says Pennisi, “is the ideal facility for developing high-performance motorcycle tires, but it is also a
place of unforgettable memories. I shared my records with
four-time world champion Fabio Villa. And it means a lot to
me that the SBK tires for the Superbike World Championship
at the Phillip Island circuit were developed at the circuit in
Apulia.” He speaks with pride, because the ring was decisive
in convincing a number of Japanese managers to choose ›
Customers & Markets
Porsche Engineering Magazine
29
2002
the W12—a car that still holds
seven records today
2004
Pirelli tires as original equipment for their motorcycles. “In
2000, we made a bid for the flying kilometer record with the
Suzuki GSX 1300 R,” explains Villa. We set it with a speed of
306.598 km/h, but this was only the average of the two runs
in opposite directions. During the second run, I had actually
hit 320 km/h.”
2002: The W12—a car that still holds seven records today
In addition to a tire, a car has also been named after the worldfamous Nardò proving ground: The Volkswagen “W12 Nardò,”
a concept car designed by Charlie Adair, was presented at the
Tokyo Motor Show in 2001. The vehicle set ten records on
April 14, 2001 with the drivers Dieter Depping, Jean-François
Hemroulle, Marc Duez, Mauro Baldi, Emanuele Naspetti,
and Giorgio Sanna. However, it was the later W12-record
version that on February 24, 2002 even exceeded the former
performance by setting a 24-hour distance and speed record
by covering 7,740.576 kilometers at an average of
322.891 km/h. The Wolfsburg-based car manufacturer had
created a 441 kW (600 hp) vehicle with 621 Nm of torque
weighing just 1,200 kilograms. Today, twelve years later, this
vehicle still holds seven world records.
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Porsche Engineering Magazine
Eliica, a 370 km / h sedan
from Japan
2004: Eliica, a 370 km/h sedan from Japan
Nine years after the Bertone record, another electric sedan
set down a clear mark. The Eliica (“Elec­tric Lithium-Ion
battery Car”) was an outlandish project developed by 40 students from Keio University in Japan, under the guidance of
Prof. Hiroshi Shimizu. The electric sedan was an eight-wheel
drive car with eight electric motors of 60 kW (80 hp) each
and a combined total of 480 kW (640 hp) powered by a bank
of 80 batteries mounted in four rows. Charging the car to a
full 100 volts took about ten hours. In 2004, the 2,100-kilogram car rocketed at 370 kilometers per hour on the ring
circuit in Apulia.
2005: New record with the Koenigsegg CCR
On February 28, 2008, Loris Bicocchi set a speed record of
388 km/h with the Koenigsegg CCR on the circular track. The
Swedish sports car powered by a 4.7-liter V8 produced
601 kW (806 hp) and 920 Nm of torque. It is relatively simple to drive on the Nardò circuit at up to 240 km/h, as at this
speed the driver doesn’t need to steer in the outermost lane.
At this relatively moderate speed, the car behaves as though
Customers & Markets
2005
New record with
the Koenigsegg CCR 2012
it were driving in a straight line. However, at faster speeds the
driver has to keep correcting the driving line with the steering
wheel. Even though Bicocchi tried to steer as little as possible
during the attempt in order to minimize tire wear, he still
reached a steering angle of 30°.
Panamera Diesel, 24 Hours
Challenge, Economy Run
average speed of approximately 120 km/h, with consumption
of 6.1 l/100 km, in line with the values declared by the manufacturer.
2012: Panamera Diesel, 24 Hours Challenge, Economy Run
Who knows what surprises the next record attempt in Nardò
holds in store? Technology evolves constantly, and humanity
continues to love pushing back the boundaries of progress. n
In recent years, the focus of vehicle testing has shifted from
pure performance to efficiency. In 2012, Porsche Italia organized the “Panamera Diesel, 24 Hours Challenge, Economy
Run.” The purpose behind this electrifying 24 Hours was
highlighting the road-racing features offered by the comfort
and reduced fuel consumption of the Porsche Panamera
­Diesel, one year after it came onto the market. The winning
strategy was focusing on the efficiency of the Panamera
­Diesel: the drivers who simply attempted to save fuel, with
an absolute peak of 18.9 km/l, were beaten by the drivers
who combined this with the highest speed. Basically, it was
unnecessary to go slowly and, on the contrary, the maximum
saving could actually be made with the car travelling at the
speed limit according to the Highway Code. The three
Panam­era cars covered a total distance of 7,967 km at an
Panamera Diesel: Fuel consumption (combined) 6,4 l/100km;
CO2 emissions (combined) 169 g/km; Efficiency class: B
Customers & Markets
Porsche Engineering Magazine
31
The return
____ Compact and light, yet powerful, highly efficient, and innovative—this is how
Porsche returned to the top class LMP1 of endurance racing. With the development of
the 919 Hybrid, the engineers once again pushed their core expertise to the limit and
thereby enabled an impressive comeback.
The engineers of the participating carmakers accepted the challenge of
reducing the energy consumption of the vehicles. The result: Race cars sent
out to the track with very different solutions under their bodies.
Andreas Seidl, Posche team boss, Wolfgang Hatz, board member for Research
and Development of Porsche AG, and Fritz Enzinger, LMP1 head (from left
to right) follow the performance of the Porsche vehicles from the pit.
The 24 Hours of Le Mans is the most famous endurance
race in the world. Back in 1951—production of the first
sports car in Stuttgart-Zuffenhausen has only been under way
since March of the preceding year—a small contingent from
Porsche KG braves the high-speed course 200 kilometers west
of Paris. The class victory of the light-alloy 356 SL Coupé
in its very first start marks the beginning of one of the great
legends of motor racing: Porsche and Le Mans. Only Porsche
has been at the start for 63 years running, and the reward for
this remarkable staying power is a series of records, including
16 triumphant overall victories and 102 class victories. The
sporting competition and the success at the top level of motor
racing at one of the most famous venues belong to Porsche
just as much as the number combination 911.
ment and the efficiency formula are revolutionary challenges,
and in the end Porsche customers will profit from that.”
The return in 2014
Since 1998, Porsche had not started in the top class Le-MansPrototype-1 (LMP1) of endurance racing. The Stuttgart-based
sports car manufacturer returned to the fray this year and
answered the new FIA efficiency rules, which limit energy
consumption per lap, with the innovative 919 Hybrid. Wolfgang Hatz, board member for Research and Development
at Porsche AG, announced the return to the top class of the
sports car World Endurance Championship (WEC) as follows:
“We remain ideally positioned in the GT area, but it was simply time for the brand to return to the top echelon of motor
racing. As far as I can remember, there has never been a set of
rules that granted engineers so much freedom and demanded
so much innovative ingenuity. (…) The hybridization require-
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Porsche Engineering Magazine
New rules
Not only Porsche’s return to Le Mans, but also the technically demanding rules, were practically revolutionary this
year: With a reduced fuel consumption requirement in place,
the Fédération Internationale de l’Automobile (FIA) and the
Automobile Club de l’Ouest (ACO) are making the fastest
race cars in the world fit for the future. To stoke innovation, the engineers were given unprecedented freedom—the
FIA and ACO declined to prescribe a uniform hybrid system. And there were no limits on either displacement or the
number of cylinders. Diesel or gasoline, turbo or not—the
decision was up to the engineers. Whether one or two recuperation systems, battery storage, ultracapacitor or flywheel,
nothing was off-limits. So the engineers at the participating
carmakers tinkered to beat the band, weighing the benefits
and disadvantages of every parameter. Viewed from the outside, the companies came to similar conclusions, but a closer
look revealed that under the bodies, the developments could
scarcely have been more different.
919 Hybrid: the technology
In its design of the combustion engine, Porsche opted for an
approach that matches the brand DNA: A gasoline engine
fires the new Porsche 919 Hybrid. It’s an extremely compact
Porsche up Close
and highly charged 2-liter V4 with direct fuel injection and
an output of 370 kW (500 hp)—highly efficient combustion
in a downsized engine.
Porsche employed two systems for energy recuperation. On
the front axle, the 919 Hybrid recuperates the kinetic energy
released by braking. Fundamentally new is the second system:
recuperation from exhaust energy. The generator is driven by
a turbine that generates energy like a bicycle dynamo. This
energy is stored in a liquid-cooled lithium-ion battery. When
the driver calls it up from there, a several hundred hp-strong
electric motor uses it to drive the front axle. When boosted,
the 919 Hybrid transforms into a quiet all-wheeler with exceptional traction. With the development of both recuperation systems and the storage technology, Porsche AG and its
in-house engineering services provider Porsche Engineering
have advanced their core competences once again.
Race outcome and conclusion
It was a tense and exciting 24 hours, the most fiercely contested race in years. With start positions two and four coming
out of qualifying, the two hybrids showed that that they were
competitive from the get-go. After an exciting start in temperamental weather, numerous dropouts, and a comparatively
quiet night, Timo Bernhard took the lead in his Porsche 919
Hybrid after 20 of the 24 hours. At 12:36 he handed over his
car with start number 20, still in the lead, to Mark Webber.
But just 20 minutes later, the Australian slowed and rolled
back to the box on electric power alone. The cause was a damaged powertrain—irreparable for the mechanics. The second
prototype, driven by the trio Romain Dumas, Neel Jani and
Marc Lieb, had a similar outing, beginning strong and holding
its own for most of the race before falling back due to transmission trouble and finally being rolled into the pit at 12:54
while in fourth place. The car—start number 14—did return
to the track shortly before the end of the race and crossed
the finish line under its own power, but also failed to place.
In spite of the initial disappointment—especially among team
members, of course, but also the fans—in retrospect the excitement and feeling of success predominate. “In our return
to Le Mans we put on an outstanding team performance. The
dream of ending our first start in this legendary endurance
race in the Porsche 919 Hybrid on the podium very nearly
came true. For quite some time we even held the lead. We’re
now looking ahead and will be back in 2015 stronger than
ever,” concluded Matthias Müller, Chairman of the Executive
Board of Porsche AG. In spite of missing the LMP1 victory,
one winner of Porsche’s return to the top class was decided
even before the race got under way: the customer. The insights and sharpened development expertise will have a direct
impact on the series models of the future. n
In the pit, every second counts:
Whether the 919 Hybrid can win
the day with its innovative recuperation systems does not depend
solely on the development expertise
of the engineers. The performance
of the team on the track has to be
right too.
Porsche up Close
Porsche Engineering Magazine
35
Battery Development for the 919 hybrid
____ In the course of development activities for the return to Le Mans, Porsche opted to
conduct battery development internally. Porsche Engineering has carried out a number of
successful battery projects in recent years and took over the battery development for the
new LMP1 race car—from the mechanical structure to the entire system control and testing.
By Michael Fürstner
Two recuperation systems make
the 919 Hybrid a true Porsche.
The exhaust energy recuperation
enables charging of the liquidcooled lithium-ion battery not
only when braking, but also when
accelerating.
The development of energy storage for the
919 Hybrid presented the engineers with
various challenges:
Weight problems and lack of space
Low system weight is always an important
requirement and is therefore at the top of
the priority list in motor racing as well. The
very limited space within the vehicle also
posed great challenges for the engineers.
For safety reasons, the entire system is
located next to the driver in the monocoque—in the crash-protected area with
just millimeters separating it from neighboring components. It was therefore
necessary to develop a highly compact,
extremely small and lightweight battery
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Porsche Engineering Magazine
without compromising electrical system
performance. after all, the drive motor
on the front axle of the LMP1 lays down
220 kW (300 hp) and naturally requires
a sufficient and reliable power supply to
perform its function.
high voltage
The electrical energy is stored in lithiumion cells from a123 Systems which were
specially developed for this motor racing
application and combined into compact
modules using a special welding procedure. each individual module has less than
60 volts. This modular construction is
important not least for safety reasons
when assembling the overall system since,
PorschE uP closE
in DC applications, the hazardous highvoltage range begins at 60 volts.
The overall system voltage of the 919
Hybrid is significantly above the 300–
400 volts normally found in conventional
electric vehicle applications. Higher
voltages allow the load current-bearing
components to have smaller diameters,
which in turn results in lower weights.
However, the components required for the
development of the battery control were
not immediately available from suppliers—
the system voltages in this range are found
in locomotives, for example, which for
reasons of traction are designed with
a high unit weight in mind. So all of the
required components had to be individually
developed and manufactured.
Performance and efficiency: a V4 with direct gasoline injection,
turbocharging and exhaust recuperation system for the Porsche
919 Hybrid.
Durability
The cooling system is of major importance
for the durability of the battery. In the 919
Hybrid, the Computational Fluid Dynamics
(CFD) based fluid cooling system dissipates
the waste heat so effectively that even at
full throttle only very small temperature
differences are detectable across the
entire battery. The thermal and electrical
loads on the individual cells in the system
are evenly balanced, which has a positive
effect on the durability of the battery as
a whole.
Testing to the limit
The mechanical loads on every component
in a race car are enormous. Due to the
extreme total system drive forces of the
current LMP1 hybrid cars and the all-wheel
drive used in the 919 Hybrid, the vehicle
accelerations before, during, and after
every corner are at nearly Formula One
The single electric motor distributes its power as needed via a differential
on both front wheels; the state-of-the-art battery energy control center is
positioned in the center of the vehicle.
levels due to the extreme grip. In terms of
top speeds, the LMP1s are even a bit
above that level, with top speeds of over
330 km / h achieved at this year’s Le Mans.
homologation process, the placement and
fastening of the battery was checked and
assured.
While in operation, all components must
withstand the vibrations passed on by the
extremely rigid monocoque, including
the vibrations from the drive motor and
those caused by unevenness of the
road surface. The curbs present in many
corners have centimeters-high transverse
grooves that rattle any car driving over
them to the core. For this reason, the
mount of the battery had to be designed to
provide maximum damping for precisely
these stresses while still taking up as little
space as possible and weighing
next-to-nothing.
System control and monitoring
A significant component of the system is
the integrated control unit. This includes
various components, e.g. crash and current
sensors, relay for switching off the system
and individual components, resistors and
interfaces for the power electronics,
back-up and battery management system
(BMS). The BMS monitors the entire battery
system from the temperature and voltage
values of the individual logical cells to the
calculation of the charge level by means of
special algorithms to evaluation of the
crash sensor signals. n
To ensure functionality, the newly developed system was ultimately put on the test
bench. There it had to withstand hours on
the hydraulic shaker with maximum
vibrations. In addition, in the course of the
Porsche up Close
Porsche Engineering Magazine
37
Keeping Current
Testing from the cell to the battery
____ Electromobility is of ever-greater significance in the automotive industry and requires
comprehensive expertise in the areas of battery development and management. Exploiting
the manifold potential applications of individual cells and the complex combination of them
to form modules and batteries requires extensive testing. This is the only way to ensure safe
and efficient functioning of the cell, module, battery component and complete battery under
different conditions and thus ultimately provide the desired driving performance.
By Emmanuel Dhollande, Michael Geier, Manuel Groß,
Florian Richter, Dr. Harald Schöffler
T = –20 °C
T = –10 °C
T = –00 °C
Open circuit voltage (OCV) – Charge / Discharge Comparison
T = +20 °C
T = +50 °C
at +20 °C
Discharge
Charge
4.0
3.8
3.6
3.6
3.4
Cell Voltage [ V ]
Cell Voltage [ V ]
3.4
3.2
3.0
2.8
2.6
3.2
3.0
2.8
2.4
2.6
2.2
2.4
2.0
0
100
200
300
400
500
600
0
Standard measurements of capacity (left), open-circuit voltage (center) and internal resistance (right)
Porsche Engineering Magazine
40
60
State of Charge (SOC) [ % ]
Capacity [ mAh ]
38
20
Engineering Insights
80
100
Qualification of individual cells
Lithium-ion cells are the smallest storage units in a battery.
These are connected serially or in parallel to create modules,
which in turn are serially connected to form the battery.
The cells come in different shapes and with varying capacities. This allows an optimal selection with regard to the field
of application and, based on that, the voltage, capacity and
structure. Due to the great number of different possible applications and the lack of standardization, adequate comparison
of cells based on manufacturer specifications is not possible.
For this reason, at Porsche Engineering a baseline measurement is carried out for all relevant cells on the cell test bench
to enable the creation of an identical and thus comparable
data record of the characteristics of different cells for storage
in a database. Using this cell data, the electrical parameters
of a battery (e.g. voltage, current, and power loss) can be defined, or the specifications verified. If a commissioning party
only specifies the performance and package conditions, the
data in the cell database can be used to determine the most
suitable cell for the respective application.
The standard measurements are conducted over the entire
temperature range in the vehicle from – 30 °C to +50 °C. First
internal Resistance discharge
at 0.5 A (1.0C) – 70 % SOC
500
–30 °C
–20 °C
–10 °C
0 °C
+10 °C
+20 °C
+50 °C
450
internal resistance [ mΩ ]
400
350
300
250
200
150
100
50
0
0.1
1
10
Various cell constructions
the temperature-dependent capacity of the cell is determined.
Then the open-circuit voltage (OCV) and time-dependent
internal resistance of the cell are determined for each temperature step at different charge levels. This data enables a
sufficiently precise calculation of the static and dynamic properties of the cell to determine its suitability for the planned
battery.
In the case of special applications, the data from the standard
measurements is often insufficient to create a complete characterization. In that case, additional, more specific measurements are carried out on the test bench. Special cases such
as the performance of the cells outside of their specifications
(for extreme cold starts), changes to the standard parameters
with age, or behavior in case of failure of an individual cell
can be tested in this manner. This makes it possible to expand
and confirm the range of the battery’s potential application.
Moreover, specific measurements can enable extrapolations
to complete batteries which in turn allow performance comparisons with existing batteries based on other technologies,
such as lead-acid batteries.
›
Pulse Time [ s ]
EnginEEring insights
Porsche Engineering MAgAzine
39
CELL TEST BENCH
The cell test bench at Porsche Engineering
The cell test bench used by Porsche Engineering for such tests
integrates four measurement modules that can be operated
individually or in parallel. To increase the maximum current,
the modules can each be connected in pairs so that either two
modules can be operated at twice the current or one module
operated at four times the usual current. In parallel with the
measurement channels, up to 16 temperature sensors can be
read and their measurement values stored alongside the voltage and current values.
Voltage range
0…5V
Current range 1
4 x ±30 A
Current range 2
2 x ±60 A
Current range 3
1 x ±120 A
Current increase
<100 µs
Sampling rate
5 ms
Temperature sensors 16
ControlEthernet
Connection to Ethernet
thermal cabinet
The cells are set to the specified measurement temperature in
a climate chamber. The configurable temperature range here
is from – 30 °C to +120 °C. The climate cabinet is controlled
from the test bench. In the case of temperature changes, the
program pauses until the target temperature is reached.
The test bench is completely programmable in its own scripting language so that test plans can be created in advance or
modified from existing ones. An individual test plan runs on
all activated channels completely independently so that, for
example, the end-of-charge termination condition is carried
out for each cell individually. With higher-order measures
(for example change of cell temperature), the channels are
synchronized.
Once started, the test bench can run fully independently for
hours, days or weeks, while the current status can be monitored on the test computer at any time. There are various
safety steps so that safe operation without supervision can be
assured. Each channel has an overarching monitoring function for the minimum and maximum cell voltage as well as
an optional temperature upper limit. If one of these limits
is exceeded, the test bench switches itself off. Additionally,
individual limits can be set for each test step. If these limits
are exceeded, the current process step is terminated, but the
test plan is continued.
Cell modules on the battery test bench
Depending on the requirements of the battery design and
calculation, multiple individual lithium-ion cells are combined to form cell modules, sometimes connected serially
and sometimes in parallel. For safety reasons, the module
voltage is kept below 60 volts to avoid any danger from the
current to people touching the cell and module connections.
The cell modules feature mechanical contact protection so
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Porsche Engineering Magazine
Technical data for the cell test bench of Porsche Engineering
that once construction is complete, the cell modules can be
safely handled at any time.
After construction, the cell module is tested on the test bench.
This involves connecting the high-current connections and the
signal lines to the in-house-developed battery management
system (BMS) with the module.
The first time the unit is put into operation, first the statistical
distribution of the cell voltages is checked and, if necessary,
brought to the same voltage level through targeted discharge
of individual cells. Now a complete charge/discharge cycle is
carried out at a low current to determine the total capacity
and the voltage curve of the module. If no apparent problems
occur here, further tests are carried out with steadily increasing currents until ultimately the maximum currents are tested.
With prototypes in particular, unexpected events regularly
occur. For instance, local heat generation can indicate a poor
connection between two cells caused by production errors.
Especially, the determined internal resistance of the module
at different charge states (SOC) and high currents provides
a particularly good indication of the quality of the module.
The insights thus gained aid in the continuous improvement
of the module design and ultimately also electric and thermal
optimization.
Engineering Insights
T = –30 °C, 70 % SOC
Battery baseline tests and battery startup tests
The insulation monitor performs an important safety function
for the battery by continuously monitoring the insulation resistance between the battery and the chassis. If this insulation
resistance sinks below a critical value, the potential for an
electric shock exists. For the test of the insulation monitor, a
test resistor is connected between the housing of the battery
(chassis ground) and a battery terminal. Since the connection, for safety reasons (contact protection) has to take place
behind the battery contactors, for this test the main contactors must be closed. The insulation monitor must identify
and report the error within a certain time. A subsequent test
checks whether the insulation monitor reliably recognizes and
reports a cable break in its chassis connection. For all tests,
all data is recorded on the test bench computer to ensure
that all measurements can be evaluated and documented later.
Another test concerns the interlock (pilot line), which is run
parallel to the HV lines through the vehicle and identifies
open connectors. For this test, the contactors are switched
and subsequently the interlock line is disconnected on the
test bench. As a result, all of the battery’s contactors must
open immediately.
It is equally important for later use in the vehicle that the
intermediate circuit is correctly precharged. Premature activation of the main contactor would damage or jam it. For this
test, any test capacity can be connected to the battery output
in accordance with the converter specifications.
When all performance data (end-of-charge/end-of-discharge
voltage) and threshold values (maximum currents and coolant
temperature) for the battery is ok, further tests in which the
battery is actively charged and discharged begin.
To determine the capacity of the battery, it is charged up to
the end-of-charge voltage. This also indicates whether the
current sensor returns the correct values and whether the
individual cell voltages are homogeneously distributed. At the
end-of-charge limit the cells must be brought to the same voltage (balancing). After completion of the balancing procedure,
the capacity of the battery is determined by discharging it up
to the end-of-discharge voltage.
–100
0–50
–100
–150
Current [ A ]
After the completion and final check of the battery with the
previously individually tested modules, the baseline startup
of the battery is conducted in the high-voltage test lab. Here
we see, among other things, whether plausible voltage and
temperature values are reported by the BMS and the contactors can be switched.
–200
–250
–300
–350
–400
–450
92 Ah Lead-Acid Battery
Extrapolated 20Ah LiFePO4 Battery
Extrapolated 40Ah LiFePO4 Battery
110
Pulse Time [ s ]
Comparison of the maximum current of a lead-acid battery with lithium-ion
batteries projected from cell data with 11V discharge
Electrical characterization
If no noticeable problems occur in the baseline tests, further
tests to characterize the battery are started. An important
performance parameter here is the internal resistance of the
entire battery. For this test the battery is charged with a current pulse after a sufficiently long rest period. The internal
resistance determined in this measurement defines the maximum performance and the power loss of the battery. It also
reflects significant aging effects.
Specified driving cycles are then simulated on the test bench.
This makes it possible to test and qualify the battery with a
real driving profile. The complete contact protection and the
fireproof testing cell ensure maximum safety in the process
for laboratory personnel.
Component tests
The high flexibility on the test bench makes it possible to
test individual components and thus also individual fuses
or connecting lines to obtain data for creating electrical and
thermal models and measure the heating of the components
›
for a certain current profile.
Engineering Insights
Porsche Engineering Magazine
41
Software tests
The focus of the tests on the source-drain test bench is on the
electrical components such as cells, high-voltage connections
or contactors and is primarily used for verification of the
high-voltage battery. But the quality of BMS algorithms can
also be assessed. Validation of the BMS using “Software in
the Loop” (SIL) and “Hardware in the Loop” (HIL) tests is
a prerequisite for software tests on the test bench.
The test cases are executed either as EXAM or CANoe scripts
and allow a high degree of automation. The baseline tests
include monitoring the time parameters of the voltage and
temperature measurement by the BMS. For thermal and electrical profiles, the distribution of this data is analyzed using
MATLAB. Defective contacts can be localized this way. Increased connector impedance leads to thermal hot-spots and
accelerated cell aging.
The charge state of the battery is an important factor that
can be determined through charge meters and voltage-based
indicators. Characteristic diagrams are usually obtained
from the cell data sheets, validated on the test bench and are
temperature-independent. The charge meter is calculated by
the current sensor integrated in the battery. This generally
represents a compromise between space, weight, accuracy
and costs. The battery’s SOC is defined by the weakest link,
i.e. the cell with the lowest charge.
To check the SOC algorithms, a charge counter is determined
based on a reference current sensor and compared with the
BMS data. Additionally, specific cells can be specifically discharged and later checked to see whether the BMS adapts
the SOC. With a battery based on lithium iron phosphate
cell technology, the SOC cannot always be determined from
a voltage indicator. In this case more complex algorithms are
applied which generally require special test cases.
One important task of the BMS is calculating the performance
of the battery, which has a major impact on driving perfor-
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Porsche Engineering Magazine
mance. For testing, the currents released by the BMS are applied to the battery in both quadrants (charge and discharge).
The changes in the current limits are monitored and compared
to the requirements.
Tests on the test bench represent an important element in
the characterization process. They also deliver important
measurement data to generate new SIL vectors for the BMS
development. These have the advantage of always being
reproducible.
Thermal tests
The thermal test bench is directly connected to the battery test
bench, which enables highly flexible testing options. Depending on the internal resistance and current, the waste heat from
a battery with a 300 kW traction output is around 6 kW due
to the high electrical efficiency. This waste heat is dissipated
into the environment through a coolant medium.
For the thermal characterization of batteries at Porsche
Engineering, various tests are conducted. Different measurement parameters are recorded on the cell, module and
battery level depending on the cooling system and stage of
development. For precise characterization, up to 40 thermal
elements can be mounted in one module to determine the
thermal paths. Another important figure is the mass flow
of the cooling medium, which in conjunction with the inlet
and outlet temperatures of the cooling medium can be used
to calculate the cooling performance. The waste heat of the
battery can be determined through the internal resistance of
the lithium-ion-cells.
The thermal start-up tests also include the stress test. Here a
current profile is applied to the battery until it has achieved
thermal balance. This is the case when the waste heat of the
battery is equal to the cooling performance of the cooling
system. In this state the thermal resistance is calculated which
determines the cooling capacity of the battery.
Engineering Insights
Porsche Cayenne S E-Hybrid
In a hybrid vehicle like
the Porsche Cayenne S
E-Hybrid, optimum
battery management is
of supreme importance.
The Cayenne S E-Hybrid is the first plug-in hybrid in the premium SUV segment. The technological
advancement compared to the previous Cayenne S Hybrid is immense: It has a lithium-ion drive
­battery with a capacity of 10.8 kWh, which enables a purely electric range of 18 to 36 kilometers
depending on driving style and terrain. The power of the electric motor has more than doubled
from 34 kW (47 hp) to 70 kW (95 hp). Overall fuel consumption (combined) is now 3.4 l / 100 km
(CO2 emissions (combined) are 79 g / km and electricity consumption (combined) is 20.8 kWh / 100km).
The combined power of the 3-liter V6 (245 kW / 333 hp) supercharged engine and the electric
motor of 306 kW (416 hp) at 5,500 rpm as well as total torque of 590 Nm at 1,250 to 4,000 rpm
enable sports car-worthy performance figures: zero to 100 km/h in 5.9 seconds and a top
speed of 243 km / h. The electric top speed is 125 km/h. The drive battery can be charged via
the electricity grid or while driving.
The battery is also subjected to dynamic driving cycles according to the specified requirements. This involves checking for a
balanced temperature distribution both within the individual
cell and within the complete battery system as a whole. The
tests also determine the permissible operating temperatures
at which the system can provide the required performance
without safety or durability concerns. Typical driving cycles
include the Artemis cycle (CADC 150), highway cycles and
various racing profiles.
Because almost all batteries that are tested on the test bench are
also completely developed and produced at Porsche Engineering, the engineers have an ideal understanding of precisely how
the units are equipped with temperature measurement points.
Conclusion
Using the described procedure and test methodology, all battery components are tested both individually as well as in
terms of their interaction to ensure their functionality and
especially their safety during the application. n
Cayenne S E-Hybrid: Fuel consumption (combined) 3.4 l/100 km;
Electricity consumption (combined) 20.8 kWh/100 km;
CO2 emissions (combined) 79 g/km; efficiency class A+
Engineering Insights
Porsche Engineering Magazine
43
Imprint
Porsche Engineering
Magazine
ISSUE 2 / 2014
Issue 2/ 2014
Porsche Engineering
CUSTOMERS & MARKETS Records on the circular track at Nardò
PORSCHE UP CLOSE Battery development for the Porsche 919 Hybrid
ENGINEERING INSIGHTS High-voltage testing from the cell to the battery
MACAN MOdELS: Fuel consumption (combined) 9.2 – 6.1 l/100 km; C02 emissions (combined) 216 – 159 g/km; Efficiency class: E–B
Porsche Engineering MagazIne
IntEllIgEnt thErmal managEmEnt
MagazIne
Issue 2 / 2014
www.porsche-engineering.com
IntellIgent
THERMAL MANAGEMENT
Insight into new solutions
Publisher
Porsche Engineering Group GmbH
Porschestrasse 911
71287 Weissach
Germany
Tel. +49 711 911 0
Fax +49 711 911 8 89 99
Internet: www.porsche-engineering.com
Editor-in-Chief
Frederic Damköhler
Editing | coordination
Nadine Guhl
Advertisement
Frederic Damköhler
Design
VISCHER&BERNET, Stuttgart
Translation
RWS Group GmbH, Berlin
Printing
Kraft Druck GmbH
76275 Ettlingen
www.porsche-engineering.com
44
Porsche Engineering Magazin
Imprint
All rights reserved. Reprinting, incl. excerpts,
only with the permission of the publisher.
No responsibility can be taken for the return of
photos, slides, films, or manuscripts submitted
without request. Porsche Engineering is a
100% subsidiary of Dr. Ing. h.c. F. Porsche AG.
www.porsche-nardo.com
All-round testing in a perfect circle.
Nardò Technical Center.
www.porsche-consulting.com
Why just satisfy customers
when you can also inspire them.
Porsche Consulting.
Fuel consumption
(in l/100
km) combined
3.1–3.0;
emissions
combined
72–70 72
g/km;
consumption
12.7 kWh/100
km
918 Spyder:
Fuel consumption
(in l/100
km) combined
3.1 CO
– 3.0;
C02 emissions
combined
– 70 electricity
g/km; electricity
consumption
12.7 kWh/100
km
2
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