Technical�training.
Product�information.
BMW�Service
Charging�the�high-voltage�battery.
General�information
Symbols�used
The�following�symbol/schematic�diagram�is�used�in�this�document�to�facilitate�better�comprehension or�to�draw�attention�to�very�important�information:
Contains�important�safety�information�and�information�that�needs�to�be�observed�strictly�in�order�to guarantee�the�smooth�operation�of�the�system.
Information�status�and�national-market�versions
BMW�Group�vehicles�meet�the�requirements�of�the�highest�safety�and�quality�standards.�Changes in�requirements�for�environmental�protection,�customer�benefits�and�design�render�necessary continuous�development�of�systems�and�components.�Consequently,�there�may�be�discrepancies between�the�contents�of�this�document�and�the�vehicles�available�in�the�training�course.
This�document�basically�relates�to�the�European�version�of�left-hand�drive�vehicles.�Some�operating elements�or�components�are�arranged�differently�in�right-hand�drive�vehicles�than�shown�in�the graphics�in�this�document.�Further�deviations�may�arise�as�a�result�of�the�equipment�specification�in specific�markets�or�countries.
Additional�sources�of�information
Further�information�on�the�individual�topics�can�be�found�in�the�following:
• in�the�operating�instructions�of�the�high-voltage�charger
• in�the�Integrated�Service�Technical�Application.
Contact:�conceptinfo@bmw.de
©2012�BMW�AG,�Munich,�Germany
Reprints�of�this�publication�or�its�parts�require�the�written�approval�of�BMW�AG,�Munich The�information�contained�in�this�document�forms�an�integral�element�of�the�technical�training�of the�BMW�Group�and�is�intended�for�the�trainer�and�participants�in�the�seminar.�Refer�to�the�current respective�information�systems�of�the�BMW�Group�for�any�changes/additions�to�the�technical�data.
Information�status:�May�2012
Charging�the�high-voltage�battery.
Contents.
1. Introduction....5
1.1. BMW�EfficientDynamics...5
1.2. Definition�and�reasons�for�hybrid�cars...7
1.2.1. Definition�of�the�hybrid�cars...7
1.3. Classification�according�to�power...9
1.3.1. Micro�hybrid�cars...9
1.3.2. Mild�hybrid...11
1.3.3. Full�hybrid...12
2. System�components....14
2.1. Energy�storage�device...14
2.1.1. Physical�principles�of�the�chemical�store...14
2.1.2. Battery�types...17
2.1.3. Summary...22
2.2. Power�electronics...23
2.2.1. General�converter...23
2.2.2. Rectifier...24
2.3. Electromechanical�switch�contactor...24
2.4. High-voltage�battery�unit...26
2.4.1. Structure�of�the�high-voltage�battery�unit...26
2.4.2. Transport�mode...33
2.5. High-voltage�charger...33
2.5.1. Lines�and�connectors...35
3. Safe�work....37
3.1. Basic�physical�effects...37
3.1.1. High�electrical�voltage...37
3.1.2. High�electrical�current...38
3.2. Dangers�posed�by�electricity...40
3.2.1. Perfusion�of�the�human�body...40
3.2.2. Electric�arc...43
3.3. Safety�rules�for�averting�danger...46
3.3.1. Basic�information...46
3.3.2. Disconnect�the�system�from�the�power�supply...47
3.3.3. Establish�that�the�system�is�isolated�from�the�power�supply...49
3.4. Other�dangers�by�hybrid�technology...49
3.4.1. Lithium-ion�battery...49
3.5. First-aid�measures...51
3.5.1. Basic�information...51
3.5.2. Immediate�measures...53
3.5.3. Send�emergency�call...55
Charging�the�high-voltage�battery.
Contents.
3.5.4. First-aid�measures...56
3.5.5. Help�by�emergency�service�and�medical�aftercare...58
3.6. Safe�work�practices�for�working�on�high-voltage�components...59
3.6.1. Prerequisites...59
3.6.2. Technical�safety�precautions...59
3.6.3. Special�features�for�working�on�high-voltage�components...67
4. Charging�the�battery....68
4.1. Introduction...68
4.2. Charging�procedure...69
4.2.1. Initial�situation...69
4.2.2. Preparing�high-voltage�charger...70
4.2.3. Opening�the�packaging�of�the�high-voltage�battery�unit...71
4.2.4. Connecting�the�high-voltage�battery�unit...73
4.2.5. Charging�the�high-voltage�battery�unit...76
4.2.6. Disconnecting�the�high-voltage�charger...78
4.2.7. Documentation�of�the�charging�procedure...79
5. Faults�and�support....80
5.1. Faults�and�support...81
5.2. Voltage�supply�of�the�high-voltage�charger�is�interrupted...81
5.3. Cancelling�the�charging�procedure...81
Charging�the�high-voltage�battery.
1.�Introduction.
1.1.�BMW�EfficientDynamics
BMW�EfficientDynamics�is�the�communicative�umbrella�term�for�a�variety�of�technologies�and innovations,�which�produce�fewer�emissions�while�at�the�same�time�lead�to�an�increase�in�power�and enhanced�driving�pleasure.�With�BMW�EfficientDynamics�BMW�has�assumed�a�leading�global�role in�the�measures�for�reducing�consumption�and�CO2.�Today�over�one�million�owners�of�new�BMW cars�have�been�benefiting�from�this�since�spring�2007.�However,�BMW�EfficientDynamics�is�more than�just�high�precision�injection,�engine�start-stop�function�or�brake�energy�regeneration.�BMW EfficientDynamics�also�includes�BMW�active�hybrid,�the�combination�of�a�combustion�engine�with electric�motors�in�the�powertrain.
At�the�end�of�2009�the�first�hybrid�versions�of�the�BMW�X6�(E72)�and�BMW�7-Series�(F04)�were introduced.�The�next�generation�of�BMW�hybrid�cars�was�built�at�the�end�of�2011�with�the�BMW ActiveHybrid�5�(F10H).�This�hybrid�car�employs�the�second�generation�of�the�high-voltage�batteries (Gen.�2.0),�which�are�also�installed�in�the�new�BMW�ActiveHybrid�7�(F01H/F02H)�and�BMW
ActiveHybrid�3�(F30H).
The�high-voltage�batteries�for�the�BMW�ActiveHybrid�X6�(E72�)�and�BMW�ActiveHybrid�7�(F04)�still originate�from�the�cooperation�ventures�with�other�automobile�manufacturers,�whereas�the�high- voltage�battery�used�in�the�BMW�ActiveHybrid�5�(F10H)�is�"Made�by�BMW".
Generations�of�active�hybrid�cars�to�date
Charging�the�high-voltage�battery.
1.�Introduction.
Index Explanation
1 The�BMW�conceptX6�ActiveHybrid�was�launched�on�the�market�at�the�end of�2009�as�the�first�BMW�hybrid�car.�The�technology�used�here�(so-called generation�1.0)�was�a�product�created�by�the�cooperation�venture�between General�Motors,�DaimlerChrysler�and�BMW.�A�nickel�metal�hydrid�battery�was used�as�an�electric�energy�storage�device.
2 The�second�hybrid�car�from�BMW�came�on�the�market�in�2010�with�the�name ActiveHybrid�7.�It�is�a�mild�hybrid�car�with�1.5�generation�technology.�This technology�was�developed�together�with�Mercedes�Benz.�The�highly�efficient lithium-ion�battery�was�used�in�the�high-voltage�electrical�system.
3 The�so-called�Generation�2.0�of�the�hybrid�cars�at�BMW�is�used�for�the ActiveHybrid�5.�The�drive�system�comprises�a�225�kW/306�HP�6-cylinder spark�ignition�engine�with�BMW�TwinPower�Turbo�technology�and�a�hybrid- specific�8-speed�automatic�gearbox�with�an�integrated�electrical�machine.
The�electrical�energy�is�stored�in�a�lithium-ion�battery�which�was�developed�by BMW.
4 The�BMW�ActiveHybrid�7�is�the�second�hybrid�car�to�use�so-called
"Generation�2.0"�hybrid�technology.�The�energy�storage�device�used�here�was adopted�from�the�ActiveHybrid�5.
5 Generation�2.0�hybrid�technology�is�also�used�in�the�BMW�ActiveHybrid�3.
What�does�BMW�ActiveHybrid�represent�and�what�is�the�difference�to�hybrid�cars�from�competitors?
BMW�ActiveHybrid�essentially�describes�all�hybrid�activities�of�BMW�aimed�at�achieving�higher efficiency�–�the�word�"Active"�should�highlight�the�particularly�dynamic�requirement�of�all�BMW�hybrid models.�The�two�different�types�of�hybridization�are�summarised�under�BMW�ActiveHybrid:�full�hybrid and�mild�hybrid.
They�are�essentially�distinguished�by�the�following:
Full�hybrid:
• Powerful�electric�drive�with�a�power�that�enables�driving�by�purely�electric�means
• High�potential�to�reduce�consumption�and�emissions,�particularly�in�urban�traffic
• Excess�weight�and�less�available�stowage�space�as�a�result�of�hybrid�components�and batteries
• High�component�and�manufacturing�costs.
Mild�hybrid:
• Small�electric�motor,�used�for�supporting�the�combustion�engine�("Boost"�function)
• Electric-only�driving�is�not�possible
• Moderate�potential�to�reduce�consumption:�Particularly�advantageous�in�urban�traffic
• Slight�increase�in�weight�and�additional�space�requirement�by�smaller�hybrid�components
• Manufacturing�costs�higher�than�for�the�standard�powertrain,�but�less�than�for�the�full�hybrid.
Charging�the�high-voltage�battery.
1.�Introduction.
Hybrid�is�only�integrated�in�the�hybrid�strategy�of�BMW�where�costs�and�savings�potential�are appropriately�interrelated.�A�start�was�made�with�large�models�with�large�engines�such�as�the�BMW ActiveHybrid�X6�and�the�BMW�ActiveHybrid�7�because�the�greatest�efficiency�potential�exists�here.
To�realise�this�approach,�the�modular�system�"Best�of�Hybrid"�is�used�at�BMW,�i.e.�the�optimal�hybrid components�(full�or�mild�hybrid�components)�are�integrated�in�different�vehicle�concepts.
1.2.�Definition�and�reasons�for�hybrid�cars
1.2.1.�Definition�of�the�hybrid�cars
Griffon�motorcycle,�Sports�model,�model�year�1906,�is�a�hybrid�vehicle
The�term�"hybrid"�comes�from�Greek�and�actually�means�"dual�origin�or�mixed�origin".�For�the definition�in�the�automotive�industry�this�now�means�that�vehicles�are�equipped�with�two�drive�types (energy�types)�and�have�two�energy�storage�devices.�The�special�feature�is�that�the�elements�brought together�are�already�solutions�in�themselves,�but�by�their�combination�can�also�create�new�desired properties.�The�most�widely�used�combination�of�these�two�drive�types�by�the�different�automotive manufacturers�is�the�combination�of�a�combustion�engine�and�electric�motor�with�two�energy�sources in�the�form�of�a�fuel�tank�and�a�battery.
Reasons�for�hybrid�cars
The�advantages�of�the�hybrid�drive�primarily�lie�in�low�consumption,�but�also�in�the�fact�that�the electric�motor�absorbs�all�unfavourable�operating�ranges�of�the�combustion�engine.�In�addition,�the characteristic�curves�of�the�electric�motor(s)�and�combustion�engine�complement�each�other�better�as the�lower�torque�of�the�combustion�engine�(in�the�lower�engine�speed�range)�is�ideally�supplemented by�the�higher�torque�of�the�electric�motor.�Furthermore,�the�brake�energy�regeneration�can�have�a positive�effect�on�the�actual�brake�wear�(minimisation�of�existing�brake�wear).
Energy�recovery�for�vehicles
The�principle�of�energy�recovery�for�vehicles�is�based�on�the�principle�of�conservation�of�energy.
Charging�the�high-voltage�battery.
1.�Introduction.
The�principle�of�conservation�of�energy�states�that�the�total�energy�of�a�closed�system�does�not change�over�time.�The�energy�can�in�fact�be�converted�between�different�energy�forms,�for�example from�heat�to�kinetic�energy.�However,�it�is�not�possible�to�create�or�destroy�energy�in�a�closed�system.
The�total�energy�in�a�closed�system�remains�constant.�The�energy�can�thus�not�arise�from�nothing and�also�cannot�simply�disappear.�Different�energy�types,�for�example�kinetic�energy,�thermal�energy, radiation�energy�or�binding�energy,�only�convert�into�one�another.�From�a�technical�perspective however,�they�are�generally�considerably�more�difficult�to�use�subsequently.
For�hybrid�cars�their�kinetic�or�potential�energy�is�converted�to�heat�energy�by�braking�and�to�electrical energy�by�the�electrical�machine�and�stored�in�a�battery.�This�stored�electrical�energy�can�then�be�used to�start�the�combustion�engine�or�for�electric�driving�for�example.
How�great�is�the�kinetic�or�potential�energy�of�a�vehicle?
The�kinetic�energy�is�calculated�according�to�the�following�formula:�Ekin�=�½ • m • v2.�The�mass�of�the vehicle�is�stated�in�m�and�v�is�the�speed�of�the�vehicle.
The�potential�energy�is�calculated�according�to�the�following�formula:�Epot�=�m • g • Δh.�Here�the vehicle�mass�is�m,�g�is�the�gravitational�acceleration�(9.81 m/s2)�and�Δh�the�difference�in�height.
Sample�calculations:
Kinetic�energy:�A�vehicle�mass�of�2500�kg�and�a�speed�of�100�km/h�results�in�the�kinetic�energy�of
½ • 2500 kg • (100�km/h)2.�So�that�the�units�match�the�speed�must�be�converted�to�m/s.�100�km/h equals�27.77 m/s.
Ekin�=�1250�kg�•�(27.77�m/s)2�=�964 506 Nm�(Ws)
If�the�braking�lasts�10�seconds�up�to�standstill,�the�available�power�is�P = 96 451 W.�The�electric�power is�calculated�according�to�the�formula�P = U • I.�For�a�voltage�of�12 V�the�current�obtained�would�be over�8000�A.�These�current�levels�cannot�be�used�in�a�car.�To�use�the�available�power�the�voltage�must be�increased�so�that�the�current�level�is�in�a�range�which�can�be�used�in�the�automobile�industry.�This is�also�the�reason�why�higher�voltages�are�used�for�hybrid�cars.�If�one�assumes�a�voltage�of�400 V,�then the�current�level�in�our�sample�calculation�is�241 A.
Potential�energy�of�a�vehicle
Charging�the�high-voltage�battery.
1.�Introduction.
Index Explanation
1 Maximum�potential�energy
2 Minimum�potential�energy
Potential�energy:�A�vehicle�mass�of�2500 kg�and�a�difference�in�height�of�100 m�gives�the�potential energy
Epot�=�2500�kg�•�9.81�m/s2�•�100�m�=�2�452�500�Ws.
If�taking�off�lasted�10�seconds�for�example,�then�the�available�power�is�P = 245 250 W.�For�a�battery voltage�of�400 V�the�current�level�is�613 A.
The�above�calculations�are�very�simplified,�but�they�give�a�feeling�of�the�magnitudes�of�energy,�power and�resulting�current�level.
1.3.�Classification�according�to�power
The�hybrid�cars�can�be�classified�into�three�groups�based�on�the�power�of�the�electric�motors:
• Micro�hybrid�cars
• Mild�hybrid�cars
• Full�hybrid�cars
The�following�table�shows�the�key�characteristics�of�each�hybrid�car�group:
Power of�the electric motor
Voltage�range Possible�functions Fuel�savings
Micro�hybrid 2�to�3�kW 12�V -�Start-stop�function under�10%
Mild�hybrid 10�to�15
kW 42�V�to�150�V -�Start-stop�function -�Boost�function -�Energy�recovery
under�20%
Full�hybrid >�15�kW >�100�V -�Start-stop�function -�Boost�function -�Energy�recovery -�Electric�driving
over�20%
1.3.1.�Micro�hybrid�cars
General�information
The�micro�hybrid�cars�are�the�first�level�of�hybrid�cars.�Micro�hybrid�cars�have�an�generator�power�of 2�to�3�kW�and�conventional�12�V�battery�technology.�The�low�power�and�voltage�restricts�the�level�of energy�recovery�during�braking�or�overrun�phases.�The�electrical�energy�recovered�is�stored�in�the�12 V�vehicle�electrical�system�in�micro�hybrid�cars.�Some�of�these�systems�also�have�a�start-stop�function with�a�conventional�starter�motor�or�integrated�starter�generator.�A�disadvantage�of�the�start-stop
Charging�the�high-voltage�battery.
1.�Introduction.
function�is�the�increased�wear�on�the�crankshaft�as�a�result�of�frequent�starting-up.�The�crankshaft is�designed�as�a�frictionless�bearing�on�a�constant�rotation.�The�time�and�effort,�excess�weight�and costs�for�the�micro�hybrid�cars�are�reasonable.�However,�overall�no�more�than�10%�energy�savings�can be�expected.�If�we�were�to�strictly�depend�on�the�definition,�the�micro�hybrid�cars�are�not�hybrid�cars because�they�only�have�one�drive�type.
Micro�hybrid�solution�from�BMW
BMW�1-Series�with�automatic�engine�start-stop�function
Intelligent�generator�control
BMW�introduced�different�technologies�for�reducing�the�fuel�consumption�of�all�BMW�Group�vehicles.
One�of�these�measures�is�the�partial�energy�recovery�of�the�vehicle's�kinetic�energy.�The�intelligent generator�control�alone�can�save�up�to�3%�CO2�and�thus�fuel�depending�on�the�driving�profile.�There are�therefore�no�impacts�on�the�power�development�of�the�customer's�vehicle.�The�core�principle�of the�intelligent�generator�control�is�an�extension�of�the�charging�strategy�of�the�battery.�The�battery is�no�longer�fully�charged,�but�charged�to�a�defined�state�depending�on�different�ambient�conditions (ambient�temperature,�age�of�battery,�etc.).�The�charging�procedure�only�takes�place�in�overrun�phases of�the�vehicle�in�comparison�to�traditional�charging�strategies.�Here�the�generator�is�energised�to�its maximum,�electrical�energy�is�created�and�stored�in�the�battery.�The�generator�is�not�energised�in the�acceleration�phases�of�the�vehicle.�Thus�no�energy�and�also�no�fuel�are�used�to�create�electrical energy.�More�information�on�this�topic�can�be�found�in�the�product�information�bulletin�"Intelligent generator�control".
Automatic�engine�start/stop�function
The�reduction�in�consumption�is�achieved�by�an�automatic�shutdown�of�the�engine�when�the�vehicle is�at�a�standstill.�The�restart�is�also�effected�automatically�as�soon�as�the�corresponding�switch-on conditions�are�present.�The�MSA�has�already�been�in�use�in�vehicles�of�the�BMW�Group�since�2007 and�is�now�available�in�numerous�vehicle�models�including�those�with�an�automatic�transmission.�The MSA�function�is�located�in�the�engine�control�(DME/DDE).�For�the�MSA�function�different�information from�the�bus�system�that�is�already�available�is�used.�Furthermore,�new�sensors�are�necessary for�fault-free�function�of�the�system.�More�information�on�this�topic�can�be�found�in�the�product information�bulletin�"MSA�automatic�engine�start-stop�function".
Charging�the�high-voltage�battery.
1.�Introduction.
1.3.2.�Mild�hybrid
General�information
Classic�mild�hybrid�systems�work�at�voltages�over�42�V.�Today�the�voltages�for�these�systems
sometimes�extend�beyond�160�V.�The�power�of�the�electrical�machine�lies�in�the�range�of�10�to�15�kW.
For�these�mild�hybrid�systems�generally�electrical�machines�are�used�which�convert�part�of�the�kinetic energy�to�electrical�energy�upon�deceleration/braking.�Mild�hybrid�systems�generally�have�a�start- stop�function�whereby�the�electrical�machine�is�used�after�the�combustion�engine�has�shut�down�to restart�the�engine.�In�the�case�of�mild�hybrid�systems�the�electrical�machine�is�sometimes�also�used�to support�the�combustion�engine�for�starting-up�or�acceleration.�For�some�mild�hybrid�systems�the�fuel supply�of�the�combustion�engine�is�shut�down�if�there�is�a�sufficient�state�of�charge�of�the�high-voltage energy�storage�device�and�there�is�a�steady�journey�of�up�to�approx.�50�km/h.�The�vehicle�is�then�only driven�by�the�electrical�machine�and�as�a�result�fuel�economy�is�possible.
BMW�mild�hybrid
BMW�Concept�7-Series�ActiveHybrid
The�first�BMW�ActiveHybrid�7�(F04)�is�a�mild�hybrid�and�was�in�serial�production�from�the�end�of�2009 to�2012.�Its�hybrid�system�works�at�a�voltage�of�120�V.�As�part�of�the�mild�hybrid�concept�the�electric drive�increases�the�dynamic�potential�of�the�eight-cylinder�petrol�engine�and�reduces�consumption and�CO2�emissions�by�up�to�15�percent,�mainly�in�urban�traffic�by�brake�energy�recovery.�Larger�and heavier�hybrid�and�battery�components�are�dispensed�with,�which�in�turn�brings�advantages�in�terms of�the�vehicle�weight�and�luggage�compartment.�The�following�functions�are�available�in�the�BMW ActiveHybrid�7�(F04):
• Engine�start-stop�function
• Recuperative�braking
• Boost
• Climate�control�when�the�vehicle�is�at�a�standstill
• But�no�electric�driving.
Charging�the�high-voltage�battery.
1.�Introduction.
1.3.3.�Full�hybrid
General�information
The�full�hybrid�systems�are�characterised�by�the�fact�that�start-up�and�driving�is�fully�possible�without a�running�combustion�engine.�In�full�hybrid�systems�high-voltage�energy�devices�with�voltages�of sometimes�over�200�V�are�used.�With�these�systems�it�is�therefore�possible�to�drive�vehicles,�e.g.
for�start-up,�by�purely�electric�means�and�in�the�case�of�strong�acceleration�use�the�torque�of�the combustion�engine�and�the�electric�motor�at�the�same�time.�This�process�is�also�called�"boost".
BMW�full�hybrid
BMW�ActiveHybrid�5
Within�the�framework�of�BMW�EfficientDynamics,�the�BMW�Group�introduces�another�version of�a�hybrid�car�from�spring�2012�and�this�time�in�the�segment�of�the�5-Series�saloon.�The�BMW ActiveHybrid�5�is�the�third�series�vehicle�with�hybrid�technology.�By�combining�for�the�first�time�a�BMW six-cylinder�in-line�engine�with�an�electric�drive,�the�BMW�ActiveHybrid�5�sets�new�standards�in�sporty driving�pleasure�and�sustainability�in�this�vehicle�segment.�The�BMW�ActiveHybrid�5�is�a�full�hybrid�car with�a�lithium-ion�high-voltage�battery.
The�drive�system�of�the�BMW�ActiveHybrid�5�comprises�a�6-cylinder�in-line�engine�with�TwinPower turbo�technology�(N55B30M0),�an�8-speed�automatic�gearbox�(GA8P70HZ)�and�an�electrical machine.�The�integration�of�BMW�active�hybrid�technology�in�the�already�efficient�saloon�with�a combustion�engine�once�again�ensures�a�reduction�of�over�10�percent�in�consumption�and�emissions levels.
Charging�the�high-voltage�battery.
1.�Introduction.
The�electric�motor�of�the�BMW�ActiveHybrid�5�enables�fully�electric�driving�and�thus�emission-free driving�at�speeds�of�up�to�60�km/h.�At�an�average�speed�of�35�km/h,�the�high-voltage�battery�provides enough�energy�to�enable�fully�electric�driving�across�a�distance�of�up�to�four�kilometres.
Charging�the�high-voltage�battery.
2.�System�components.
2.1.�Energy�storage�device
The�energy�storage�devices�store�the�energy�which�is�used�at�a�later�stage.�Often�the�energy�is�stored in�another�energy�form�and�only�converted�later�if�required�to�minimise�the�drawbacks�in�the�case�of standstill�losses.�For�example�chemical�energy�(fuel)�is�stored�in�the�tank�and�converted�to�thermal and�mechanical�energy�in�the�combustion�engine.�Losses�always�occur�during�energy�storage�and energy�conversion.�There�are�many�types�of�energy�stores�(mechanical,�thermal,�chemical,�magnetic and�electrostatic).�The�following�provides�a�more�detailed�description�of�the�chemical�stores,�as�these are�used�most�frequently�in�today's�hybrid�cars�as�a�second�energy�source.
2.1.1.�Physical�principles�of�the�chemical�store
Basic�structure�of�a�voltaic�cell
Index Explanation
1 Negative�electrode
2 Electrolyte
3 Separator
4 Positive�electrode
In�principle�a�voltaic�cell�comprises�the�electrolyte,�the�battery�housing�and�of�course�the�two electrodes.�In�addition,�the�electrodes�are�insulated�from�one�another�by�a�permeable�separator�for ions�and�an�impermeable�separator�for�electrons.�There�are�chemical�reactions�in�the�voltaic�cells, which�result�in�an�electron�excess�at�one�electrode�and�an�electron�shortage�at�the�other.�Electrical voltage�thus�arises�between�these�two�electrodes.
When�the�battery�is�discharged�the�chemical�energy�stored�is�converted�to�electrical�energy�by a�chemical�reaction.�The�energy-supplying�reaction,�the�discharging,�is�made�up�of�two�spatially separated,�but�connected�partial�reactions�(electrode�reactions).�The�electrode�with�which�the corresponding�partial�reaction�runs�for�a�redox�potential�lower�in�comparison�to�the�other�electrode is�the�negative�electrode,�and�the�other�the�positive�electrode.�An�oxidation�process�takes�place at�the�negative�electrode�for�the�discharging�of�the�cell,�during�which�electrons�are�released;�the corresponding�amount�of�electrons�are�absorbed�at�the�positive�electrode�via�a�reduction�process.�The electron�current�flows�through�an�outer�consumer�circuit�from�the�negative�to�the�positive�electrode.
In�the�cell�the�current�between�the�electrodes�is�carried�by�ions�in�the�ion-conducting�electrolyte�("ion current"),�whereby�ion�and�electron�reactions�are�connected�in/at�the�electrode.
Charging�the�high-voltage�battery.
2.�System�components.
The�voltaic�cells�are�used�as�DC�voltage�sources.�The�combination�of�electrode�materials�gives�the voltaic�cell�its�name,�such�as�nickel�metal�hydride�cell.�Depending�on�whether�the�cell�is�charged�or discharged,�the�composition�of�the�electrolyte,�as�well�as�the�electrode�material,�changes.�The�type�of materials�from�which�the�electrodes�are�produced�is�determined�by�the�nominal�voltage�of�the�cell.
The�term�"battery"�describes�the�interconnection�of�several�voltaic�cells�which�are�used�as�an�energy source.�But�an�individual�voltaic�cell�is�also�called�a�"battery"�in�normal�usage.�Voltaic�cells�convert�the chemical�energy�stored�within�directly�to�electrical�energy.�A�distinction�is�made�between�rechargeable and�non-rechargeable�batteries.�The�difference�lies�in�the�fact�that�in�rechargeable�batteries�the reactions�for�the�discharging�are�largely�reversible�and�the�battery�can�always�be�recharged�and discharged.�Multiple�conversions�of�chemical�to�electrical�energy�and�vice�versa�are�thus�possible.
Series�connection�of�voltaic�cells
If�a�higher�voltage�is�required�than�the�actual�cell�voltage,�the�cells�can�be�connected�in�series.�The total�voltage�of�the�battery�then�corresponds�to�the�sum�of�the�individual�cells.�In�the�example�above the�total�voltage�is�Utot�=�U1�+�U2�+�U3.
Parallel�circuit�of�voltaic�cells
The�capacity�of�the�battery�is�increased�by�a�parallel�circuit�of�the�voltaic�cells.�The�voltage�of�the battery�thus�always�stays�the�same.
The�capacity�of�a�battery�is�the�electric�charge�stored�in�the�battery.�The�capacity�of�the�battery is�stated�in�ampere�hour�(abbreviation:�Ah).�The�available�capacity�of�a�battery�depends�on�the discharging�conditions.�The�available�capacity�decreases�with�an�increasing�discharge�current.
The�power�of�a�battery�is�stated�in�watt�and�is�the�product�of�a�discharge�current�and�discharge voltage.�The�energy�stored�in�a�battery�is�generally�not�specified.�The�energy�per�mass�or�per�volume is�however�an�important�parameter�of�battery�systems.
Energy�density�and�power�density�of�a�battery
Charging�the�high-voltage�battery.
2.�System�components.
Energy�and�power�density�of�batteries
Index Explanation
1 Double-layer�capacitor
2 Lead-acid�battery
3 Nickel�cadmium�battery
4 Nickel�metal�hydrid�battery
5 Lithium-ion�battery
x Energy�density�in�Wh/kg
y Power�density�in�W/kg
The�energy�density�describes�the�distribution�of�energy�to�the�mass�of�a�material�and�is�specified in�Wh/kg.�In�hybrid�cars�the�energy�density�of�the�energy�storage�device�used�is�decisive�for�the achievable�range.
The�power�density�of�a�battery�defines�its�electric�power�related�to�the�mass�and�is�specified�in�W/kg.
The�diagram�above�shows�the�power�density�and�energy�density�of�some�storage�devices.�For example�the�double-layer�capacitors�have�a�very�high�power�density,�but�a�low�energy�density�in comparison�to�other�storage�devices.�They�are�thus�capable�of�delivering�a�very�high�power�for�a short�period.�If�for�example�one�compares�the�nickel�cadmium�and�the�nickel�metal�hydrid�battery, one�notices�that�the�two�batteries�have�roughly�the�same�power�density.�But�the�nickel�metal�hydrid battery�has�almost�double�the�energy�density.�This�means�that�a�nickel�metal�hydrid�battery�would
Charging�the�high-voltage�battery.
2.�System�components.
only�have�half�the�weight�of�a�nickel�cadmium�battery�with�the�same�amount�of�storable�energy.�Or�if one�considers�the�range:�A�vehicle�with�a�nickel�metal�hydrid�battery�would�have�double�the�range�of�a vehicle�with�a�nickel�cadmium�battery�of�the�same�size.
Comparison�of�the�energy�densities�of�petrol�and�a�12�V�battery
Fossil�fuels�have�a�considerably�higher�energy�density.�For�example�the�petrol�or�diesel�fuel�has�an energy�density�of�11.8�kWh/kg.�A�12�V�lead-acid�battery�has�an�energy�density�of�30�Wh/kg.�This means�that�petrol�has�approx.�400�times�higher�energy�density�than�the�lead-acid�battery.�If�for example�a�12�V�battery�has�a�volume�of�approx.�12�litres,�the�petrol�would�take�a�volume�of�0.03�litres with�the�same�amount�of�energy.
There�are�several�versions�of�batteries�on�the�market.�The�following�only�describes�the�most�important battery�types,�which�are�of�interest�from�the�point�of�view�of�hybrid�technology.
2.1.2.�Battery�types
Lead-acid�battery
The�lead-acid�battery�is�one�of�the�oldest�battery�systems�(since�1850)�and�today�still�supplies�millions of�vehicles�with�electrical�energy.�The�lead-acid�battery�is�used�in�vehicles�as�a�starter�battery�for starting�the�combustion�engine.�In�addition,�it�supplies�the�electrical�consumer�with�current�over�a limited�period,�also�at�engine�standstill.
Charging�the�high-voltage�battery.
2.�System�components.
Structure�of�a�lead-acid�battery
Index Explanation
1 Seal�plug
2 Hydrometer�(magic�eye)
3 Carry�handle
4 Positive�terminal�of�the�battery
5 Battery�housing
6 Base�for�securing�the�battery
7 Disc�block�comprising�positive�and�negative�disc�set
8 Negative�terminal�of�battery
Charging�the�high-voltage�battery.
2.�System�components.
Chemical�reaction�in�a�lead-acid�battery
Index Explanation
1 Cathode�(negative�terminal)
2 Anode�(positive�terminal)
3 Sulphuric�acid
In�a�charged�state�the�positive�terminal�of�the�lead-acid�battery�is�made�up�of�lead-oxide�(PbO2)�and the�negative�terminal�lead�(Pb).�Diluted�sulphuric�acid�(H2SO4)�is�used�as�an�electrolyte.�If�the�battery�is discharged,�both�terminals�are�made�up�of�lead-sulphate�(PbSO4).
The�overall�reaction�during�discharging�can�be�shown�with�help�of�the�following�chemical�formulas:
Pb�+�PbO2�+2H2SO4�—>�PbSO4�+�2H2O2�+�electrical�energy
The�cells�are�essentially�made�up�positive�and�negative�electrodes,�separators�and�the�parts�necessary for�the�assembly.�Each�cell�supplies�a�voltage�of�two�volts.�6�cells�are�connected�in�series�for�a�battery voltage�of�12�V.�The�energy�density�of�the�lead-acid�battery�is�approx.�30�Wh/kg.
Nickel�cadmium�battery
The�nickel�cadmium�battery�(NiCd)�was�developed�over�100�years�ago�and�is�still�in�use�today.�An essential�difference�to�the�lead-acid�battery�is�that�the�electrolyte�remains�unchanged�during�charging and�discharging.�In�a�charged�state�the�electrodes�of�a�nickel�cadmium�cell�are�made�up�of�panels, which�are�loaded�with�cadmium�at�the�negative�terminal�and�nickel�hydroxide�at�the�positive�terminal.
Potassium�hydroxide�is�used�as�an�electrolyte.�This�combination�supplies�a�voltage�of�1.2�V.�The energy�density�is�comparable�to�that�of�a�lead-acid�battery.
The�heavy�metal�cadmium,�which�is�harmful�to�the�environment,�and�the�so-called�memory�effect�are the�main�causes�for�the�replacement�of�NiCd�batteries�with�new�battery�systems.�The�memory�effect is�described�as�the�capacity�loss�which�occurs�in�the�case�of�very�frequent�partial�discharge�of�a�nickel cadmium�battery.�The�battery�seems�to�"notice"�the�energy�requirement�for�the�previous�discharge processes.�Instead�of�the�original,�nominal�energy�quantity�the�battery�only�delivers�a�minimal�energy quantity�and�the�voltage�drops.
Charging�the�high-voltage�battery.
2.�System�components.
Nickel�metal�hydrid�battery
Nickel�metal�hydrid�battery�in�the�ActiveHybrid�X6
The�nickel�metal�hydrid�battery�(NiMH�battery)�is�often�considered�the�successor�of�the�NiCd�battery.
The�NiMH�cell�supplies�a�nominal�voltage�of�1.2�volts.�The�energy�density�of�a�NiMH�battery�is�roughly 80�Wh/kg�and�is�thus�double�that�of�a�NiCd�battery.�The�memory�effect�described�above�hardly�ever occurs�in�the�case�of�the�NiMH�battery.�Within�a�short�period�it�can�deliver�its�stored�electrical�energy at�almost�constant�voltage.
The�NiMH�battery�is�sensitive�to�overloading,�total�discharging,�overheating�and�incorrect�polarity.�It�is also�temperature-sensitive.�It�has�a�significant�capacity�loss�near�freezing�point.
The�anode�is�made�from�a�metal�alloy�which�can�store�hydrogen�reversibly�by�storing�it�in�crystal�lattice and�thus�forming�a�metal�hybrid.�The�electrolyte�contains�20�percent�potassium�hydroxide�solution�in which�the�cathode�made�from�nickel�hydroxide�is�also�located.
The�hydrogen�is�oxidised�during�discharging.�A�voltage�of�1.32�volts�occurs�at�both�electrodes�as�a result.�So�that�the�metal�is�not�oxidised�instead�of�the�hydrogen�at�the�end�of�the�discharging�process, the�negative�electrode�is�much�larger�in�size�than�the�positive�electrode.
Lithium-ion�battery�(li-ion�battery)
The�development�of�lithium�batteries�with�lithium�metal�anodes�and�non-aqueous�electrolytes�began in�the�1960s.�The�non-rechargeable�lithium�batteries�were�first�used�in�space�travel�and�for�military applications.�Due�to�their�minimal�self-discharging�they�are�still�also�used�today�in�pacemakers,�clocks and�cameras.�The�actual�commercial�breakthrough�of�the�rechargeable�lithium�battery�came�with the�market�introduction�of�a�cell�which�completely�dispenses�with�metallic�lithium,�the�lithium-ion battery.�Li-ion�cells�are�used�today�mainly�for�the�energy�supply�of�portable�devices�with�a�high�energy requirement�(mobile�phones,�digital�cameras,�notebooks,�etc.).�Due�to�its�high�energy�density�they�are also�of�particular�interest�for�use�in�electric�and�hybrid�cars.�In�addition,�they�supply�a�constant�voltage over�the�entire�discharge�period�and�have�no�memory�effect.
Charging�the�high-voltage�battery.
2.�System�components.
Structure�of�a�li-ion�cell
Index Explanation
1 Positive�electrode
2 Housing�with�electrolyte
3 Lithium�metal�oxide
4 Separator
5 Graphite�layer
6 Negative�electrode
7 Lithium-ion
The�positive�electrode�of�the�most�frequently�used�li-ion�cells�is�made�up�of�lithium�metal�oxides�in several�layers�(e.g.�LiCoO2�or�LiNiO2).�The�negative�electrode�is�made�up�of�several�layers�of�graphite.
Both�electrodes�are�in�an�electrolyte�free�of�water.�A�separator�is�located�between�the�two�electrodes.
The�lithium-ion�battery�generates�the�source�voltage�by�shifting�the�lithium�ions.�During�the�charging procedure�of�the�cell�positively�charged�lithium�ions�are�converted�by�the�electrolyte�of�the�anode�into the�graphite�layers�of�the�cathode.�The�lithium�ions�form�a�bond�with�the�graphite�(carbon)�without destroying�the�molecular�structure�of�the�graphite.�During�discharging�the�lithium-ions�convert�back into�metal�oxide�and�the�electrons�can�flow�via�the�outer�circuit�to�the�positive�electrode.�The�formation of�a�protective�surface�layer�on�the�negative�electrode�is�essential�for�bonding�the�lithium�ions�and�the graphite�layer.�This�layer�is�permeable�for�the�small�lithium�ions�and�impermeable�for�molecules�in�the electrolyte.
Li-ion�batteries�have�minimal�self-discharging�and�their�efficiency�is�roughly�96%�due�to�the high�ability�to�move�of�the�lithium�ions.�The�efficiency�is�temperature-dependent�and�decreases considerably�at�a�lower�temperature.
A�conventional�li-ion�cell�supplies�a�nominal�voltage�of�3.6�volts.�The�voltage�of�a�lithium-ion�battery is�also�three�times�that�of�a�nickel�metal�hydrid�battery.�A�total�discharge�to�under�2.4�volts�leads�to irreparable�damage�and�capacity�loss�of�the�cell�and�therefore�the�voltage�cannot�fall�below�this�level.
Charging�the�high-voltage�battery.
2.�System�components.
The�specific�power�density�lies�in�the�range�of�300�to�1500�W/kg.�The�energy�density�is�roughly double�that�of�the�nickel�cadmium�battery�for�example�and�is�95�to�190�Wh/kg.
Discharging�of�the�lithium-ion�battery�under�40�%�should�be�avoided�as�this�can�lead�to�larger�capacity losses�due�to�irreversible�reactions�in�the�electrodes.�Also�the�battery�ages�quicker�the�higher�its�cell voltage�is.�For�this�reason�it�should�also�be�avoided�that�the�lithium-ion�battery�is�constantly�charged�at 100�%.�The�optimal�state�of�charge�is�between�50�%�and�80�%.
There�are�some�special�features�to�note�when�handling�lithium-ion�batteries.�The�mechanical�damage of�the�battery�can�cause�a�short�circuit�of�the�cell.�The�housing�could�melt�and�catch�fire�as�a�result of�the�high�current�level.�Li-ion�batteries�are�in�fact�hermetically�sealed,�nevertheless�they�should�not be�immersed�in�water.�Lithium-ion�batteries�react�very�strongly�in�water,�particularly�in�a�fully�charged state.
As�lithium-ion�batteries�have�a�production-related�fluctuation�of�different�parameters,�e.g.�capacity, and�a�battery�is�composed�of�many�cells,�the�cells�must�be�monitored�individually.�This�is�the�job�of�the battery�management�system.�This�system�ensures�that�the�individual�cells�do�not�overload�or�become heavily�discharged�and�it�arranges�a�charge�balance�between�the�cells�if�necessary.
2.1.3.�Summary
As�we�have�seen�the�voltaic�cell�is�the�core�of�a�storage�system.�Therefore�the�number�of�suitable�cells is�decisive�for�the�storage�device�properties.�The�following�table�provides�an�overview�of�the�properties of�the�key�electrical�energy�storage�devices.
Energy storage device
Cell�voltage
in�volt Power
density�in W/kg
Energy density�in Wh/kg
Memory
effect Operating
temperature in�°C
Lead-acid
battery 2 up�to�500 30 - up�to�45
Nickel cadmium battery
1.2 up�to�1.000 40 yes up�to�65
Nickel�metal
hydrid�battery 1.2 up�to�1.000 80 low up�to�60
Lithium-ion
battery 3.6 300�to�1,500 95�to�190 no up�to�50
If�the�voltage�and/or�the�capacity�of�the�cell�is�not�sufficient�for�the�application,�several�cells�can�be connected�in�series�or�parallel.
Cells�connected�in�series�and�parallel�circuit�of�cells
Charging�the�high-voltage�battery.
2.�System�components.
2.2.�Power�electronics
Power�electronics�is�a�sub-area�of�electrical�technology,�but�also�includes�the�electronic�components whose�job�is�to�switch,�control�and�convert�electrical�energy.�The�components�and�circuits�of�the power�electronics�are�made�up�of�silicone�diodes�and�silicone�thyristors.�These�components�can switch�very�high�voltages�and�currents�(up�to�4500�V�and�1500�A).
Silicone�transistors�and�silicone�triacs�are�also�used�in�the�lower�power�range.�Thyristors�are circuit�elements�whose�switch-on�time�can�be�set�or�adjusted�by�a�control�voltage�at�the�control electrode,�the�gate.�Two�thyristor�elements�in�one�component,�which�are�connected�in�parallel�in�the opposite�direction�and�are�controlled�jointly,�is�called�a�triac.�The�conversion�of�electrical�energy�with transformers�or�using�rotating�machine�sets�is�not�calculated�for�the�power�electronics.�The�power electronics�primarily�enables�the�conversion�of�electrical�energy�relating�to�the�voltage�type,�the�level of�voltage�and�current,�as�well�as�the�frequency.
2.2.1.�General�converter
Converter�and�inverter
Charging�the�high-voltage�battery.
2.�System�components.
Index Explanation
1 Rectifier
2 DC-DC�converter
3 Inverter
4 AC-AC�converter
The�circuits�for�conversion�of�electrical�energy�related�to�the�voltage�type,�as�well�as�the�level�of voltage�and�current,�are�called�converters.�Depending�on�their�function�a�distinction�is�made�between rectifier,�inverter�and�converter.
The�conversion�of�AC�voltage�to�direct�current�voltage�is�effected�using�a�rectifier.�Direct�current voltage�can�also�be�converted�to�AC�voltage.�Inverters�are�used�for�this�purpose.�The�conversion of�direct�current�voltage�to�a�higher�or�lower�direct�current�voltage�is�effected�using�a�DC-DC converter.AC-AC�converters�are�used�for�the�conversion�of�AC�voltage�to�AC�voltage�at�a�different height�(amplitude).�If�the�frequency�of�the�AC�voltage�should�change,�frequency�converters�are required.�In�hybrid�cars�the�power�electronics�is�required�for�the�conversion�of�direct�current�voltage to�AC�voltage�and�vice�versa.�In�addition,�the�operating�points�of�electrical�machines�can�be�set�very flexibly�with�help�of�power�electronics.
2.2.2.�Rectifier
Circuit�symbols�for�rectifiers
Rectifiers�are�used�for�the�conversion�of�AC�voltage�to�direct�current�voltage.�They�comprise�several diodes�which�become�rectifiers�by�their�interconnection.�The�diodes�direct�the�respective�half-waves of�the�AC�voltage�to�a�common�direction,�so�that�a�pulsating�direct�current�voltage�arises.�To�obtain pure�direct�current�voltage,�the�voltage�must�be�smoothed�after�the�rectifier�by�means�of�a�capacitor or�throttle.�The�rectification�can�be�uncontrolled�by�semi-conductor�diodes�or�controlled�with�help�of thyristors.�Controlled�rectifiers�require�a�control�voltage�which�specifies�at�what�time�which�electronic circuit�has�to�be�opened�and�closed�in�order�to�achieve�a�rectifying�effect.�Controlled�rectifiers�are realised�by�electronic�circuit�elements�such�as�thyristors�and�MOSFET.�In�the�case�of�uncontrolled rectifiers�the�rectification�of�the�AC�voltage�takes�place�without�an�additional�control�electronics.
2.3.�Electromechanical�switch�contactor
An�electromechanical�switch�contactor�is�an�electrical�switch�for�high�switching�capacities.�The operating�principle�of�a�switch�contactor�is�the�same�as�that�for�a�relay.�However,�the�power,�which can�be�switched�via�a�switch�contactor,�is�much�higher�and�ranges�from�500�watt�to�several�hundred kilowatt.
Charging�the�high-voltage�battery.
2.�System�components.
Operating�principle�of�a�relay
Index Explanation
A Switch�contactor�open
B Switch�contactor�closed
1 Voltage�source�(low�voltage)
2 Switch�for�low-voltage�circuit
3 Coil�(magnet)
4 Armature
5 Normally�open�contact
6 Load�current�circuit�with�consumer
A�coil�is�activated�via�a�switch�in�a�low-voltage�circuit.�As�soon�as�the�low-voltage�circuit�is�closed, the�induced�magnetic�field�of�the�coil�moves�an�armature.�This�closes�the�circuit�of�the�high-voltage circuit.�As�soon�as�the�low-voltage�circuit�is�reopened,�the�magnetic�effect�of�the�coil�is�removed.�The armature�is�then�reset�to�the�initial�position�by�a�spring.�The�high-voltage�circuit�is�also�interrupted�as�a result.
The�switching�contacts�of�electromechanical�switch�contactors�are�generally�double-break,�i.e.�the high-voltage�circuit�is�generally�separated�by�the�switch�contactor�at�two�points.
Charging�the�high-voltage�battery.
2.�System�components.
Circuit�symbols�for�switch�contactor
In�extreme�cases,�for�example�extremely�high�current�levels,�the�normally�open�contacts�may�"stick".
If�this�occurs,�the�high-voltage�circuit�can�no�longer�be�interrupted�by�the�electromechanical�switch contactor
2.4.�High-voltage�battery�unit
2.4.1.�Structure�of�the�high-voltage�battery�unit
The�term�"high-voltage�battery"�refers�to�the�actual�energy�accumulator�for�the�high-voltage�system.
In�addition�to�the�energy�storage�device,�other�components�are�required�in�the�vehicle�in�the�high- voltage�battery�unit�to�ensure�maintenance�and�safety�in�the�vehicle.�In�this�chapter�the�structure�of�a high-voltage�battery�unit�using�the�example�of�the�high-voltage�battery�unit�Gen.�2.0�is�described.
The�nominal�voltage�of�316.8 V�is�achieved�by�a�series�connection�of�a�total�of�96�battery�cells (nominal�voltage�3.3 V).
The�high-voltage�battery�unit�is�made�up�of�8�cell�modules.�Each�cell�module�comprises:
• 12�cells
• Cooling�extruded�profiles�(5�centrepieces�and�2�side�pieces)
• Cell�contact�system�ZKS.
Charging�the�high-voltage�battery.
2.�System�components.
Structure�of�cell�module
Index Explanation
1 Cell
2 Cooling�extruded�profile,�centrepiece
3 Cell�module
4 Cooling�extruded�profile,�side�piece 5 Bracket�for�cell�contacting�system 6 Cell�connector,�cell�contacting�system
The�individual�lithium-iron-phosphate�cells�from�A123�Systems�are�cylindrical�in�shape.�These cells�are�lithium-ion�batteries�whose�cathodes�are�made�from�lithium-iron-phosphate.�They�are characterised�by�their�high�load�capacity�and�robustness.�Another�advantage�of�the�lithium-iron- phosphate�cells�as�opposed�to�other�lithium-ion�batteries�is�that�there�is�no�oxidation�material�in�the cell�and�therefore�overreactions�are�less�severe.
Charging�the�high-voltage�battery.
2.�System�components.
The�cells�are�bonded�in�the�cooling�extruded�profiles.�In�general,�the�adhesive�tape�should�have�high thermal�conductivity�to�ensure�good�heat�dissipation�from�the�cell�to�the�extruded�profile.�In�the�event of�damage�to�the�plastic�sleeve�of�the�cell�the�adhesive�must�also�have�an�insulating�effect.
The�two�parts�of�the�cell�contacting�system�ZKS�are�welded�to�the�cell�terminal�by�means�of�a�laser welding�process.�This�provides�the�series�connection�of�the�individual�cells.
There�are�two�power�taps�in�each�module�to�discharge�the�current�from�the�module.�The�power taps�are�attached�at�the�front�cell�contacting�system.�The�power�taps�of�neighbouring�modules�are connected�to�the�module�connectors.
Lithium-ion�technology�cells�are�sensitive�to�overloading,�overvoltage,�overcurrent�and�excess
temperature.�For�this�reason�printed�circuit�boards�for�voltage�taps�are�fitted�at�the�cells�with�integrated temperature�sensors�on�both�sides�of�the�cell�module.�The�monitoring�of�the�cells�is�effected�by�the cell�supervision�circuits�CSC�(Cell�Supervising�Circuit).
The�cell�modules�are�installed�in�a�vaporising�unit�to�cool�the�cells.�The�refrigerant�is�routed�along�the cells�through�channels�in�the�heat�sink�and�the�cells�cooled.
Structure�of�the�high-voltage�battery�unit
Charging�the�high-voltage�battery.
2.�System�components.
Index Explanation
1 Housing�cover
2 Shield�including�current�arrester
3 Cell�supervision�circuit�CSC
4 Battery�management�electronics�(SME)
5 Heat�sink�incl.�crash�plates
6 Retaining�bracket
7 Housing
8 Cell�module
The�housing�of�the�high-voltage�battery�unit�Gen.�2.0�cannot�be�opened.
The�passing�of�forces�in�the�event�of�a�crash�through�the�heat�sink�and�thus�along�the�cell�modules�is realised�by�so-called�crash�plates.�These�are�located�between�the�cell�modules.
If�an�impermissible�high�temperature�or�impermissible�high�pressure�arises�in�a�cell,�a�pressure�relief value�is�integrated�in�both�covers�of�each�cell�beside�tight�and�weldable�terminals.�Above�this�point�the excess�pressure�in�the�cell�can�be�decreased.�The�gases�released�in�the�process�are�discharged�from the�vehicle�through�the�degassing�pipe.
The�high-voltage�battery�can�be�connected�to�or�isolated�from�the�high-voltage�electrical�system�using the�contacts�of�electromechanical�switch�contactors�inside�the�high-voltage�battery�unit�of�the�vehicle.
These�contacts�are�located�on�the�positive�terminal�and�the�negative�terminal,�before�the�terminals�of the�high-voltage�battery�are�routed�outwards.�The�electromechanical�switch�contactors�are�activated by�a�control�unit�in�the�high-voltage�battery�unit,�the�so-called�battery�management�electronics�SME.
Battery�management�electronics
High�demands�are�placed�on�the�service�life�of�the�high-voltage�battery�(service�life�of�the�vehicle).�In the�interest�of�satisfying�these�demands,�it�is�not�permitted�to�operate�the�battery�in�any�manner�one likes.�Instead,�the�high-voltage�battery�is�operated�in�a�precisely�defined�range�so�as�to�maximise�its service�life.�This�includes�the�following�marginal�conditions:
• Protecting�the�cells�against�overheating�(by�cooling�and/or�limiting�the�current)
• Adjusting�the�state�of�charge�of�the�individual�cells�where�necessary�to�one�another
• Not�fully�depleting�the�battery's�amount�of�storable�energy.
For�this�reason�the�high-voltage�battery�unit�also�has�its�own�control�unit,�which�monitors�these marginal�conditions�and�intervenes�where�necessary.�This�control�unit�is�called�the�"battery
management�electronics�(SME)"�and�is�located�inside�the�high-voltage�battery�unit,�which�is�why�it�is not�accessible�from�the�outside.�The�SME�control�unit�must�fulfil�the�following�tasks:
Charging�the�high-voltage�battery.
2.�System�components.
• Determining�the�state�of�charge�(SoC)�and�the�state�of�health�(SoH)�of�the�high-voltage�battery
• Control�of�the�starting�and�shutdown�of�the�high-voltage�system
• Safety�functions�(e.g.�high-voltage�interlock�loop,�insulation�monitoring)
• Monitoring�the�voltage�and�temperature�of�the�battery�cells�and�the�current
• Communication�of�fault�status.
The�SME�control�unit�has�its�own�fault�memory�which�can�be�read�out�using�the�BMW�diagnosis system.
Cell�monitoring
Certain�conditions�must�be�observed�for�fault-free�operation�of�the�lithium-ion�cells:�The�cell�voltage and�the�cell�temperature�cannot�exceed�or�drop�below�certain�values�as�otherwise�the�battery cells�may�suffer�long-term�damage.�For�this�reason�each�high-voltage�battery�unit�has�several�cell supervision�circuits,�which�are�described�as�"Cell�Supervisory�Circuits�CSC".
The�cell�supervision�circuits�perform�the�following�functions:
• Measurement�and�monitoring�of�the�voltage�of�each�individual�battery�cell
• Measurement�and�monitoring�of�the�temperature�at�a�point�on�each�cell�module
• Communication�of�the�measured�variables�to�the�battery�management�electronics�control�unit
• Implementation�of�the�process�for�adjusting�the�cell�voltage�of�the�battery�cells.
The�measurement�of�the�cell�voltage�is�effected�at�a�very�high�sampling�rate.�The�end�of�the�charging procedure,�as�well�as�the�discharging�procedure,�can�be�identified�using�the�voltage�measurement.
Using�the�cell�temperature�an�overload�or�electrical�fault�can�be�identified.�In�such�a�case�the�current level�must�be�reduced�immediately�or�the�high-voltage�system�shut�down�completely�in�order�to�avoid progressive�damage�to�the�battery�cells.
External�interface�(S-box)
In�the�high-voltage�battery�unit�there�is�an�interface�unit�with�its�own�housing,�which�is�also�called�a
"shift�box"�or�"S-box"�for�short.
The�following�components�are�integrated�in�the�interface�unit:
• Current�sensor�in�the�current�path�of�the�negative�battery�terminal
• Safety�fuse�in�the�current�path�of�the�positive�battery�terminal
• Two�electromechanical�switch�contactors�(one�switch�contactor�per�current�path)
• Pre-charge�switch�for�slow�start-up�of�the�high-voltage�system
• Voltage�sensors�for�monitoring�the�switch�contactors�and�for�measuring�the�total�battery voltage.
High-voltage�connection
There�is�a�2-pin�high-voltage�connection�at�the�high-voltage�battery�unit.
Charging�the�high-voltage�battery.
2.�System�components.
High-voltage�connection�on�the�high-voltage�battery�unit
Index Explanation
1 Bush�with�connection�for�bridge�in�the�circuit�of�the�high-voltage�interlock�loop
2 Mechanical�locking
3 Electrical�contact�for�high-voltage�cable 4 Electrical�contact�for�shielding
5 Contact�protection
The�high-voltage�connection�not�only�fulfils�the�primary�task�of�connecting�the�high-voltage�battery unit�to�the�high-voltage�cables.�In�addition,�the�high-voltage�connection�provides�protection�against contact�with�live�parts:�The�actual�contacts�are�coated�in�plastic�so�that�nobody�can�touch�them directly.�Only�when�the�cable�is�connected�is�the�coating�pushed�away�and�the�contact�established.
The�plastic�slide�serves�as�the�mechanical�latch�mechanism�of�the�connector.�In�addition,�it�is�also an�element�of�a�safety�function:�If�the�high-voltage�cable�is�not�connected,�the�slide�conceals�the connection�for�the�bridge�of�the�high-voltage�interlock�loop.�Only�when�the�high-voltage�cable�is properly�connected�and�the�connector�is�locked,�is�this�connection�accessible�and�the�bridge�can�be inserted.�This�guarantees�that�only�when�a�high-voltage�cable�is�connected�is�the�circuit�of�the�high- voltage�interlock�loop�also�closed.�The�high-voltage�system�can�thus�only�be�active�if�the�high-voltage cable�is�connected�and�the�circuit�of�the�high-voltage�interlock�loop�is�closed.
Charging�the�high-voltage�battery.
2.�System�components.
High-voltage�connection
Index Explanation
A High-voltage�connection�with�connected�high-voltage�cable B High-voltage�connection�with�disconnected�high-voltage�cable 1 Bridge�for�high-voltage�interlock�loop�(connected)
2 Mechanical�slide
3 High-voltage�connector�of�the�high-voltage�cable 4 Bridge�for�high-voltage�interlock�loop�(disconnected) 5 High-voltage�connection�on�the�high-voltage�battery�unit
Procedure�for�connection�of�high-voltage�cable�to�high-voltage�battery�unit
Charging�the�high-voltage�battery.
2.�System�components.
Index Explanation
A Connect�high-voltage�connector
B Lock�with�slide
C Connect�bridge�of�high-voltage�interlock�loop
After�the�high-voltage�connector�is�inserted�at�the�high-voltage�battery�unit,�the�plastic�slide�must be�pushed�in�the�direction�of�the�connector.�The�high-voltage�connector�is�thus�locked�and�the connection�for�the�high-voltage�interlock�loop�free.�Then�the�bridge�of�the�high-voltage�interlock�loop can�be�positioned.�While�the�bridge�of�the�high-voltage�interlock�loop�is�connected,�the�lock�cannot�be loosened�and�thus�the�high-voltage�connector�cannot�be�disconnected.
2.4.2.�Transport�mode
The�high-voltage�battery�unit�is�in�the�so-called�transport�mode�for�transport�and�storage.�In�transport mode�some�internal�functions�such�as�balancing�of�the�individual�cells�for�example�are�switched�off.�As a�result,�the�self-discharging�of�the�high-voltage�battery�unit�is�reduced.
The�transport�mode�also�contributes�to�electrical�safety�in�that�it�prevents�the�electromechanical switch�contactors�being�able�to�be�closed.�For�charging�the�transport�mode�must�therefore�be
cancelled�by�the�high-voltage�charger�for�a�short�period.�After�the�charging�procedure�is�complete,�the transport�mode�of�the�high-voltage�battery�unit�must�be�activated�again�in�order�to�prevent�quick�self- discharging.
2.5.�High-voltage�charger
The�high-voltage�charger�HVL1�was�developed�by�Eltek�for�the�high-voltage�battery�unit�Gen.�2.0.�The software�of�the�high-voltage�charger�can�be�updated�to�allow�improvements�from�development.
High-voltage�charger�HVL1
Charging�the�high-voltage�battery.
2.�System�components.
Index Explanation
1 Brief�instructions
2 Display�with�pushbuttons
3 Emergency-off�switch
4 Network�switch
5 Signal�connector
6 Mains�plug
7 Label�for�high-voltage�component
8 Ventilation�grille
9 Connection�for�equipotential�bonding�(is�not�used�when�charging�the�high- voltage�battery�unit)
10 High-voltage�connector
Brief�instructions�on�using�the�device�can�be�found�on�the�front�of�the�device.�These�serve�only�as reference.�When�charging�high-voltage�batteries�always�observe�the�operating�instructions�enclosed with�the�high-voltage�charger.
The�high-voltage�charger�has�the�following�operating�and�display�elements:
Operating�and�display�elements�of�high-voltage�charger�HVL1
Index Explanation
1 Display
2 Display�of�voltage�supply�of�high-voltage�charger 3 Display�of�high-voltage�charging�procedure
4 Display�of�faults