Safe and reliable batteries for xEVs – AVL Battery Solutions Public
SAVE AND RELIABLE BATTERIES FOR XEV‘S
Future Powertrain Conference
February 19th / 20th 2014
AVL List GmbH Hans-List Platz 18020 Graz, Austria
Dr. Uwe WiedemannDr. Volker HennigeHarald StützBernhard KalteneggerDr. Bernhard BrunnsteinerJeremy Gaume
Safe and reliable batteries for xEVs – AVL Battery Solutions Public
CONTENT
Battery Management System for automotive applications
Crash safety
Battery cooling system – targets and CAE modeling & design approach
Results for the cooling system
Summary
2
Safe and reliable batteries for xEVs – AVL Battery Solutions Public
HAZARDS FROM SYSTEM ENVIRONMENT ANDMALFUNCTIONS OF CONTROL SYSTEM
Crash
Fire
Misuse
Flooding
…
Overcharging
Overcurrent
Low cooling
WrongSwitch-on
Function System / Environment
Controlled bySafety function
Controlled bySafety design
Over-/Undervoltage
Safe and reliable batteries for xEVs – AVL Battery Solutions Public
SYSTEM SAFETY OF BATTERY CELLS
/1/ FreedomCAR Electrical Energy Storage System Abuse Test Manual for Electric and Hybrid Electric VehicleApplications, SANDIA REPORT SAND2005-3123
Sys
tem
Saf
ety
Safe and reliable batteries for xEVs – AVL Battery Solutions Public
CONTENT
Battery Management System for automotive applications
Crash safety
Battery cooling system – targets and CAE modeling & design approach
Results for the cooling system
Summary
5
Safe and reliable batteries for xEVs – AVL Battery Solutions Public
DECENTRALIZED BMS ARCHITECTURE – HW&SWSOLUTION
List of main functions (partly distributed on BCU and MCU):
AVL‘s battery control unit (BCU) and module control unit (MCU) include:
Cell specific core algorithms Auxiliary functions Safety and diagnosis functions Interface and communication options for active / passive balancing
State of charge (SOC) State of function (SOF) Stage of health (SOH) Balancing Cell failure detection Signal acquisition Actuator control Contactor control Pre-charge function Startup/shutdown
Charger communication Thermal management Isolation detection HV-interlock Safety monitoring Diagnostics (OBD, service) Error management CAN and service tool communication Logistics information Vehicle interface
BCU
MCU
ISO 26262
Safe and reliable batteries for xEVs – AVL Battery Solutions Public
BMS APPLICATION SOFTWARE – NEW CHALLENGES
State of the art BMS functions usually calculate:
state of charge
state of health (basic version)
state of function (i.e. power limitations)
thermal behavior
These are essential functions for vehicle operation of a production level BMS, but…
How do we determine when a pack seems to be in relatively good condition, whereas in reality it is about to fail?
How do we know how long our pack will last?
critical regarding introduction of new cell technologies
7
Reliability means:
high accuracy
robust
high validation degree
tested with aged cells
Safe and reliable batteries for xEVs – AVL Battery Solutions Public
BMS APPLICATION SW – HOW TO DETECT CELL FAILURES
AVL’s cell wear detection function
monitors single cell SOC deviations compared to the average
monitors cell resistance deviations compared to the average
early detection of impending cell faults (unexpected SOC or resistance deviation)
warning before pack failure to avoid vehicle breakdown
8
cellvoltage
time
average cell voltage
cell voltage red: higher SOC, lower resistance
cell voltage blue: higher SOC level, higher resistance
open-circuit voltage
over-voltage
cell voltage - average cell voltage
average cell over-voltage
cell voltage red: higher SOC, lower resistance
cell voltage blue: higher SOC level, higher resistance
negative slope indicatinga lower cell resistance
offset related to higher SOC level
Fig. a) cell voltage response @ charging. Fig. b) linear model for cell voltage deviations.
Safe and reliable batteries for xEVs – AVL Battery Solutions Public
BMS application SW: Cell wear warning in real life
Measurement data showing response to failing cells in a pack.
9
After two weeks of battery operation, the detected cell failedcompletely: +100% increasein resistance....
Error manager: warning flag due to 30% higher cell resistance (detected after 100s)
Safe and reliable batteries for xEVs – AVL Battery Solutions Public
CONTENT
Battery Management System for automotive applications
Crash safety
Battery cooling system – targets and CAE modeling & design approach
Results for the cooling system
Summary
10
Safe and reliable batteries for xEVs – AVL Battery Solutions Public
STANDARDS AND LEGAL REQUIREMENTS
Legal requirements for vehicle crash
• ECE R94 – Frontal collision
• ECE R95 – Lateral collision
• ECE R100 – electric powertrain – post crash & safety requirements
• FMVSS 214 – Side impact protection.
• FMVSS 224 – Rear impact protection
General requirements for vehicle crash
• IIHS – Insurance Institute for Highway Safety
• Euro NCAP
Front & Side crash, EuroNCAP - Renault ZoeSource : http://www.carsafetyrules.com
EuroNCAP FRONTAL IMPACTInitial speed of the vehicle =
64km/hDeformable barrier with 40%
overlap
Source : http://www.euroncap.com
EuroNCAP CAR TO CAR SIDE IMPACT
Deformable barrierInitial speed of the barrier =
50km/h
Source : http://www.euroncap.com
Safe and reliable batteries for xEVs – AVL Battery Solutions Public
STANDARDS CONCERNING BATTERY AND VEHICLE CRASH
• ISO 6469-4 – Electrically propelled road vehicles — Safety specifications — Part 4: Post crash electrical safetyProtection against: - Fire- High voltage- Electrolyte spillage- Short circuit
• ISO 12405-3 – Safety performance requirements- Inertial load at vehicle crash- Contact force at vehicle crash
• SAE J1766 – Recommended Practice for Electric and Hybrid Electric Vehicle Battery Systems Crash Integrity Testing
• FreedomCAR – Electrical Energy Storage System Abuse Test Manual for Electric and Hybrid Electric Vehicle Applications- Crush- Drop test- Mechanical shock
Example of the penetration test (nail)Source : http://www.auto-motor-und-sport.de/
Safe and reliable batteries for xEVs – AVL Battery Solutions
DESIGN PROCESS AVLCRASH SAFETY FOR AN AUTOMOTIVE BATTERYFor each design phase, AVL strategy consists in :
1. SLED TEST SIMULATIONS => EVALUATION OF THE BATTERY PACK (AVL)
- Explicit simulation model composed of the sled device and the complete battery package with main components :housing, cooling units, battery modules, main electric components
- Pulse curves (inputs) coming from customers : front, side and rear crash
- Analysis of : o integrity (no fissure, no rupture) of the housing, cooling
units and module cellso integrity of joining techniques : connections with the vehicle
(BIW), weldings, brackets, …o dynamic and static displacements
AVLSled tests simulations
Communication AVL-Customer
AVLSpecial loadcases
CustomerIntegration in complete
vehicle
Example of a sled test deviceSource : http://www.seattlesafety.com/products
Safe and reliable batteries for xEVs – AVL Battery Solutions
DESIGN PROCESS AVLCRASH SAFETY FOR AN AUTOMOTIVE BATTERY
2. SPECIAL LOADCASES => EVALUATION OF THE BATTERY PACK (AVL)
- Definition with the customer of specific loadcases and requirements : e.g. Pole tests, local part intrusions, …
- Evaluation of local deformations : e.g. local deformations onmodule cells
- Evaluation of current carrying parts (e.g. internal shorts)
For each design phase, AVL strategy consists in :
AVLSled tests simulations
AVLSpecial loadcases
Communication AVL-Customer
CustomerIntegration in complete
vehicle
Example of dynamic battery testings
Safe and reliable batteries for xEVs – AVL Battery Solutions
DESIGN PROCESS AVLCRASH SAFETY FOR AN AUTOMOTIVE BATTERY
AVLSled tests simulations
AVLSpecial loadcases
CustomerIntegration in complete
vehicle
Communication AVL-Customer
For each design phase, AVL strategy consists in :
3. INTEGRATION OF THE BATTERY PACK IN COMPLETE VEHICLE=> EVALUATION (OEM)
- Integration of the battery pack simulation model (include) in complete vehicle model - Simulations realised by the OEM
- Analysis of battery pack behaviour : o integrity of the connecting parts : bolts pack-vehicle,
structural parts of the BIWo integrity of battery pack : possible contacts with
environment, local deformations on module cells, … Front crash, Volvo C30Source : http://www.autobild.de
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OVERVIEW OF A TYPICAL DESIGN PROJECT PHASE 2 : RESULTS OF THE 2nd LOOP
ANIMATION Final status -upper view
Final status – cross section
Final status – lower view
Analysis : Improvement of the global behaviour of the housing but the structure integrity of the package is still NOT ACCEPTABLE
rupture process remaining in few weak areas
rupture process remaining in the lower corner of the housing : NOT
OK
Some rupture process still remaining for the connections
modules-housing
rupture process remaining in few weak
areas
contribution of the side
reinforcements
rupture process remaining for the connections module-
housings
Safe and reliable batteries for xEVs – AVL Battery Solutions Public
OVERVIEW OF A TYPICAL AVL DESIGN PROJECTCORRELATION PHASE : TESTS versus SIMULATIONS
Correlation between simulations and tests
- Detail : Comparison of the global behaviour of the battery package:
-crash kinematic, global displacement, relative displacements, … Evaluation of the possible deformations occured during the test and comparison with the
simulations Evaluation of the sensors data : accelerometers, …
- Example of a correlation result: rupture of a frame during sled test
Rupture of the frame in test
Rupture of the frame in simulation
Safe and reliable batteries for xEVs – AVL Battery Solutions Public
CONTENT
Battery Management System for automotive applications
Crash safety
Battery cooling system – targets and CAE modeling & design approach
Results for the cooling system
Summary
18
Safe and reliable batteries for xEVs – AVL Battery Solutions
COOLING SYSTEM DESIGN
Targets for the cooling system:
Optimal cooling performance in accordance to the vehicle requirements
Minimal temperature gradient – is a ∆T of 2 K realistic and needed?
Minimum weight and high mechanical integration
Results for the cooling system:
Contribution to overall battery pack weight
Chosen materials and & manufacturing methods
Simulation vs. measurement results
Safe and reliable batteries for xEVs – AVL Battery Solutions
THERMAL INTEGRATION REQUIREMENTS OF AN AUTOMOTIVE BATTERY
Battery Pack Life
Maximum temperature (cycling, storage) Minimum temperature (charging) Temperature distribution on pack and cell
Vehicle (Battery) Performance
Reduced cell performance at low temp. Reduced pack performance at high temp.
Safety
Avoid thermal event within the packEnergy Efficiency
Cooling energy Heating energy
Energy Efficiency
Battery Pack Life
Vehicle Performance
Passive Safety
Thermal integration and thermal management of an automotive battery is one of the key points for a safe, durable and energy efficient system.Thermal integration and thermal management of an automotive battery is one of the key points for a safe, durable and energy efficient system.
Safe and reliable batteries for xEVs – AVL Battery Solutions
CELL MODEL VALIDATION PROCESS WITH MEASURED LOAD PROFILE ON THE TEST BED
Measured el. current load profile from EVARE test track run „Graz - Lassnitzhöhe“ used for cell model validation.
Electrical and thermal measurements conducted within the testing program on the cell for the load profile.
Lumped mass heat transfer model for 0D transient simulation
Safe and reliable batteries for xEVs – AVL Battery Solutions
FAST SIMULATION MODEL FOR BATTERY SYSTEM COOLING EVALUATION
),,( TISOCfQ ~~~~~~~~
~~ ~~~~~~~~
~~
Direct liquid cell tab /bus bar cooling for a inner cell is modeled in 1D considering all relevant boundary conditions: thermal resistance of the cell and tabs heat transfer at the cooling interface according
to CFD analysis adiabatic at the main cell surfaces
Based on measurements and results of structural temperature simulation the 1D model is calibrated.C
oolin
g su
pply
Section view
Cooling supply
Distributor
cell tab
Temperature results due to constant current discharge
Schematic build up of 1D modelT
x
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MATERIALS AND PROPERTIES
Part Material conductivity[W/mK]
[kg/m³]
Electric conductivity [Si/mm]
Specific heat [J/kgK]
Side plates AVL_AW_ALMGSI1 – T651 165 2700 38300 896 Neg. Tab Copper 305 8940 43000 386 Pos. Tab Aluminum 215 2700 35000 900 Bus bars Copper 305 8940 43000 386 Electrode XXX_Cell 50 2.2 50 2380 13742., 0.022222, 13742 664 Active layer HeatGen_Layer 50 2.2 50 2380 According to cell model 700 Insulation pad Insulation material 16 200 0 1000 Compression pad ProtectION PF40 0.086 250 0 200
Material properties of the active cell material are defined according to the cell model and cell measurements in the AVL cell laboratory
Cell active layerCopperFoamed polymerCopper terminalAluminum terminalCompression padElectrodes
Safe and reliable batteries for xEVs – AVL Battery Solutions Public
CONTENT
(Functional) Battery safety
Battery Management System for automotive applications
Crash safety
Battery cooling system – targets and CAE modeling & design approach
Results for the cooling system
Summary
24
Safe and reliable batteries for xEVs – AVL Battery Solutions Public
ELECTRO THERMAL PERFORMANCE ANALYSIS RESULTS @ 3C (123A) CONSTANT CURRENT DISCHARGE
Direct liquid cell tab/bus bar cooling is calculatedExtreme thermal loading condition for cooling system design.Simulation conditions: 3C constant current discharge Cooling condition
TWater inlet = 25°C @ 20l/minHTCavg = 950W/m²K No heat exchange with ambient
Simulation results: No steady state condition reached temperature peaks at 49°C at the
end of the cycle temperature difference on the cells
~3°C
Safe and reliable batteries for xEVs – AVL Battery Solutions
LIQUID COOLING SYSTEMCOOLANT CIRCUIT SIMULATION AND OPTIMIZATION
Design facts:• Weight of complete cooling system: 5.5 kg• Weight of coolant only: 2 kg
• Weight of cooling system / total pack weight: 2.2%by pure cell tab cooling
1D CFD analysis employed to optimize the coolant circuit:• Coolant flow distribution to equalize cooling conditions for all
module stacks• Optimization of pressure drop in the system• Calculation of thermal boundary conditions for thermal
analysis
Safe and reliable batteries for xEVs – AVL Battery Solutions
Chosen Materials and Production Technologies for the Cooling System:
Production Technologies:For the cooling system only production methods were selected which allow cost optimized mass production:
1) Injection Molding2) Extrusion
Components:1) Coolant Distributors: injection molded (PPE+PS GF15)2) Coolant Pipes: extruded (PPE+PS GF15)3) Standard rubber hoses4) Standard hose clamps5) 2 turned parts as inlet/outlet interfaces6) Thermal conductive glue
Required Tools:Only two tools are necessary:
1) one die for injection molding2) one extrusion die
27
LIQUID COOLING SYSTEM
Safe and reliable batteries for xEVs – AVL Battery Solutions Public
CONTENT
Battery Management System for automotive applications
Crash safety
Battery cooling system – targets and CAE modeling & design approach
Results for the cooling system
Summary
28
Safe and reliable batteries for xEVs – AVL Battery Solutions Public
SUMMARY & CONCLUSION
Many new innovations will be in software and electronics (BMS)
Crash safety requirements can be a cost driver and have to be met
Innovation is often in conflict with reliability and robustness
Simulation tools enhance maturity during development stages
29
Safe and reliable batteries for xEVs – AVL Battery Solutions Public
AVL BATTERY SOLUTIONS
THANK YOU FOR YOUR ATTENTION!
For more information
www.avl.com/battery
ANIMATION
NO RUPTURE ANYMORE:
STRUCTURE INTEGRITY OK
ANIMATION
rupture of the housing: NOT OK
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