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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


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


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


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


CONTENT


Crash safety



Summary

5


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


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


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.


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)


CONTENT


Crash safety



Summary

10


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


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


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 :





vehicle

Example of dynamic battery testings


DESIGN PROCESS AVLCRASH SAFETY FOR AN AUTOMOTIVE BATTERY




vehicle


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


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


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


CONTENT


Crash safety



Summary

18


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


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.


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


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


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


CONTENT

(Functional) Battery safety


Crash safety



Summary

24


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


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


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


CONTENT


Crash safety



Summary

28


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


AVL BATTERY SOLUTIONS

THANK YOU FOR YOUR ATTENTION!

For more information

www.avl.com/battery

[email protected]

ANIMATION

NO RUPTURE ANYMORE:

STRUCTURE INTEGRITY OK

ANIMATION

rupture of the housing: NOT OK

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