Page 1 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Fraunhofer IISB - Battery Systems
Li-lon Batteries for Stationary Energy Storages
Your R&D Partner for Innovative Solutions in Advanced Battery Systems
Page 2 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Presentation Outline
1. Introduction ; Motivation ; Cost Analys is
2. Competences and Development Flow
3. Battery Modelling and State Estimation (SOx)
4. Battery Management System (BMS)
5. Temperature Sensor & Gas Sensor for Safety
6. Antifuse for Enhanced Reliability and Availability
7. Conclusion and Outlook
Page 3 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
DC-Grid: Integration of a Stationary Battery System
100 kW
Bidirectional
DC/DC-Converter
100 kW
20 kWh
Li-Ion Battery
Page 4 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Modular Battery Management System
Fraunhofer IISB
Fraunhofer IISB Fraunhofer IISB
Universal Battery Junction Box
Modular Battery System
System Topology LTO chemistry 20Ah prismatic cells 14 daisy-chained
modules 15s2p Modules Electrical Specifications 20kWh total energy 100kW maximum
continuous power 320A continuous charge
and discharge currents 315..567V voltage range 1.2mV precise voltage
monitoring at cell level High electronic
reliability achieved through redundant design for 24/7 grid applications
Air cooled system
Full-Custom High-Performance Stationary Battery System
Page 5 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Cost Analysis: Lead-Acid versus Lithium-Ion
Based on the estimation made by: http://www.powertechsystems.eu/en/technics/lithium-ion-vs-lead-acid-cost-analysis
Specifications Value
Energy that must be stored (usable) 50kWh
Discharge power 10kW (i.e., 5 hours runtime at C/5)
Cycling frequency 1 discharge/charge cycle per day
Average ambient temperature 23°C
Expected lifespan 5475 cycles (~15 years at 1 cycle per day)
Chemistry Lead-Acid AGM Lithium-Ion (LFP) Lithium-Ion (LTO)
Installed capacity 100kWh 62.5kWh 50kWh
Usable capacity 50kWh 50kWh 50kWh
Lifespan 3000 cycles @ 50% DOD 3000 cycles @ 80% DOD 6000 cycles @ 100% DOD
Battery cost 15,000€ (150€/kWh) (x2) 18,750€ (300€/kWh) (x2) 75,000 (738€/kWh) (x1)
Installation cost 2,000€ (x2) 2,000€ (x2) 2,000€ (x1)
Transportation cost 2,800€ (28€/kWh) (x2) 625€ (10€/kWh) (x2) 700€ (14€/kWh) (x1)
Total cost 19,800€ (x2) 40,125€ (x2) 77,700 (x1)
Cost per installed kWh (over 15 years)
0.79€/kWh 0.86€/kWh 0.79€/kWh
For the considered battery cell chemistries, a use-case can be found so that the considered chemistry offers a cost advantage. The central question is: does this use-case make sense in a commercial application?
Page 6 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Required Competences for Designing Battery System Solutions
Development and assembly of battery packs with
their thermal management system
Development of electrical, mechanical and thermal
battery models at cell, module and pack level
Development and assembly of battery monitoring
and battery management system (BMS) hardware
Development of battery state estimation algorithms
(e.g., SOC, SOH, SOF)
Development of safety sensors (e.g., temperature
sensors) for enhanced safety in battery systems
Development of actuators (e.g., power antifuse) for
enhanced reliability and availability in battery
systems
W
L
R
R
R
Temperature Sensors on
Lithium-Ion Battery Cells
Battery Monitoring and
Management Software
Battery Monitoring and
Management Hardware
Power Antifuses
Battery Modeling
Smart Power Integrated
Driver Circuit
Page 7 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Development Flow for Battery System Solutions
Mechanical Design
• Battery Cell Assembly Design
• Battery Module Assembly Design
• Battery Pack Assembly Design
• Battery System Mechanical Design
• System Integration
Electrical Design
• Battery Junction Box Design
• Battery Monitoring Design
• Battery Management Hardware Design
• Battery Management Software Design
• Cell Voltage Equalization Design
Thermal Design
• Coupled Electro-thermal Modelling
• Coupled Electro-thermal Simulations
• Thermal Layout of the Battery System
• Thermal Management (Liquid, Air)
• Cooling & Heating
System Design
• System Specifications (e.g., Energy, Power, Size)
• Safety and Reliability/Availability Requirements
• Cells Selection (Based on our Internal Database)
• Cells Modeling (Electrical, Mechanical, Thermal)
System Fabrication
• Component Selection (e.g., Breakers, Connectors)
• Component Fabrication (e.g., Packages, Bus Bars)
• System Assembly and Integration
• Final Tests and Characterization
• Delivery of the Battery System Prototype
Page 8 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Electro-thermal Simulation Needed for Thermal Management
Electrical model
Current profile as input
Dissipation calculated with Rs is strongly temperature dependent
Thermal model
Dissipation as input
Calculate resulting temperature distribution
Issue: long FEM simulation time
Simulation:
electrical model Current
Dissipation
Simulation:
reduced thermal
model
Average
temperature
Voc
L ZW Ri
Z1 Z2 Rsd
Page 9 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Thermal Parameters Rth and Cth
Electrical Parameters
CAD Model with λth and cth
Model Order Reduction
Parameter Optimization
Electrical Model without Parameters
Electrical Model with Parameters
Coupled Electro-thermal Simulations
Reduction/expansion matrix: Expanded Model with
Temperature Distribution
BMS SOC with Kalman Filter (EKF, AEKF,
UKF)
Dimensioned Battery System
Electrical
Thermal Electro-thermal
Coupled Electro-thermal Modelling Workflow
Page 10 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Thermal Modeling Using Model Order Reduction (MOR)
Aim: generate a low dimensional approximation of the system
Mathematical method (i.e., does not rely on intuition)
CADFEM Toolbox used here
n~10000-100000; r~100
Result for a pouch cell
Mean temperature on electrode stack
Error < 0.1°C
FEM: 2000s (4 CPUs)
MOR: 5s (1 CPU) 1600:1 ratio
Physics &
Geometry
System of
n equations
Reduced system of
r << n equations FEM MOR
Page 11 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Reconstruction of the Temperature Distribution Output of MOR: mean temperature of electrode stack
MOR method reduction uses transformation matrices
Transformation matrices enable inverse transformation
Reconstruction of the temperature gradients (at 500s)
Comparison FEM/MOR with reconstruction at one time step
Error < 0.03°
Page 12 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Electro-thermal Coupling: Simulation versus Experiment
Experiment: Real Cell Heated by Discharge Cycle Thermographic imaging
Electro-thermal coupled simulation with MOR
Comparison shows good accuracy in values and distribution: ΔT<1.5°C
Thermocouple position
Measurement TC [°C]
Simulation [°C]
ΔT [°C]
Below MINUS tab 37.9 38.8 0.8
Center below tabs 35.5 36.6 1.1
Below PLUS tab 37.3 38.0 0.7
Page 13 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Battery State Estimation: Workflow and Assessment
Model with Parameters
Kalman Filter (EKF, AEKF, UKF)
SOC SOx
Temperature Measurements
Voltage Measurements
Current Measurements
Measurement Profiles
Global Optimization Multi-objective Genetic Algorithm
Simultaneous Calibration Against Multiple Profiles
Selection of Champions
Local Optimization Intense Post-Optimization • Levenberg-Marquardt • Sequential Quadratic Programming • …
Final Solution
Constraints
Measurement Synchronization
Particle Filter (Research Topic)
Fraunhofer IISB Advanced S imulation Framework
Battery Model without
Parameters
Further Developments
Required
Cutting-Edge Technology Available
Page 14 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Battery Management and Monitoring: Electronic Architecture
Features:
Battery monitoring electronics based on Linear Technology LTC6804-1 state-of-the-art battery monitoring IC
16bit resolution of voltage and temperature measurements
Electronics based on proven designs for mobile and stationary applications
Software-less monitoring electronics eliminates software problems
Safety aspects :
Redundant monitoring electronics possible (main and backup path)
Ultra low current consumption during sleep state (4µA)
+
-
Monitoring IC
Module x
Differential communication bus
MCU Gateway
IC
BMS
+
-
Monitoring IC
Module 2
+
-
Monitoring IC
Module 1
Page 15 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
DC/DC Converter
2 Isolated CAN
Transceivers
Relay Drivers
Monitoring ICs
Infineon
TriBoard
Companion IC
Infineon CIC61508
Add On Board II
Add On Board I
32 bit Microcontroller
Infineon TriCore TC1798
Infineon TriBoard
32bit TC1798 MCU
OSEK/AUTOSAR Automotive Operating System
JTAG Interface
Add On Board I
Galvanically Isolated Relay Drivers
Data Interface to Monitoring Circuits
Real Time Clock
SD Memory Card for Logging
Add On Board II
Galvanically Isolated Power Supply
Isolated CAN Interfaces (2x)
Charger Control Interface
Companion IC (Infineon CIC61508) for Safety
On Board Temperature Measurement
Isolation Monitoring Interface
Precision Voltage Reference
Interface for
Isolation
Monitoring
Battery Management System: Hardware Overview
Page 16 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Provide
Safety
Safety For
Humans
Explosion
Fire
Electric Shock
Safety for Battery
Overtemperature
Overvoltage
Overcurrent/ Short circuit
Undervoltage
Undertemperature
Enhance
Battery Lifetime
Temperature Control
Heating Demand
Cooling Demand
Electric Control
Charge Management
Power/Current Derating
Battery State Estimation
BMS Self Diagnosis
Functional State
SOC
SOH
SOF
Battery Management System: Software Overview
Page 17 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Battery Monitoring Electronics Based on the LTC6804-1
Voltage measurement of the battery system (>100 Cells) in 290µs
Accuracy of voltage measurements
Single cell: ≤1.2mV
Module: ≤1%
Quasi synchronous voltage sampling
Robust daisy chain communication
Energy consumption at 25°C: 13mA (ON) ; <10µA (SLEEP)
Fully redundant design for ASIL-D and 24/7 applications: includes functions for error&failure detection and compensation
Evaluation of up to 16 external temperature sensors per module
Passive balancing with failure correction
Fully Redundant Battery Monitoring with Failure Compensation – No Software!
Page 18 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Battery Monitoring: Redundant Solution for 24/7 Applications
Backup IC 1 Main IC 1 MUX Balancing Ctrl
MUX Temperature Measurement
Daisy Chain Connector
Temperature Sensor Connectors
Passive Balancing Cooling Area Voltage Measurement Filters
Main IC 2
Page 19 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Printed Low-Cost Flexible Temperature Sensor
High thermal sensitivity: 3% per °C
Designed for low-cost and fast manufacturing
Highly flexible substrate
Overall thickness less than 300µm
100µm flexible substrate (PI, PET etc.)
50µm screen printed contacting
layer with silver compound
50µm screen printed resistive layer
100µm passivation layer
passivation layer
resistive layer
interdigitated
electrodes layer
plastic substrate
Page 20 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Gas Sensor for Enhanced Safety in Battery Systems
The idea is to detect dangerous operating
conditions of lithium-ion battery cells by means of
the cost-effective AppliedSensor iAQ-100 module
Accurate and reliable measurement of:
Temperature
Humidity
Carbon dioxide (CO2) levels
Volatile organic compounds (VOCs)
But: only reacts to differences in temperature or
composition of the gas mix
AppliedSensor iAQ-100
Page 21 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Gas Sensor: Battery Abuse Tests
NMC Li-ion 5Ah cell abuse test
12C overcharge current
Cell mechanically fixed
No shut down after gas detection
Measurements of:
Gas (VOC/CO2)
Cell voltage
Cell temperature
Cursor 1: Initial gas detection
Cursor 2: Estimated beginning of thermal runaway Δt: 40s
Page 22 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Antifuses: New Bypass Electronic Device
Battery systems for high-power applications require stacking of ~100 cells in series
Bypass feature against single cell failure
Cell can be shorted out from the circuit
Power Antifuse Symbols
Untriggered Antifuse
Triggered Antifuse
Page 23 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Realization of Antifuse Devices
Assembly and packaging
Press-pack design
Aluminum springs
Mold compound for 600°C: K-Therm® AS 600 M
„Demonstrator sample“: Polycarbonate top housing
Designed for 100A and 1mΩ
Page 24 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Dashboard of the Battery System
Dashboard showing the major control values for the battery system:
Value: Voltages, Temperatures, Current, Power
Status: Power and Pre-charge Contactors, Galvanic Isolation, Voltages, Temperatures, Current
Battery State Estimations: SOC, SOH, SOF, SOL
Page 25 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Conclusion and Outlook: Examples of Active Research Topics
High Availability Redundant Battery Electronics (without Software
Running Locally) Addressing Safety-Critical Applications (e.g., ASIL-D)
Parametric Model-Order-Reduction Applied to Electro-thermal Battery
System Models for Simulating Cycles at System Level (e.g., NEDC, WLTP)
Reduction of Temperature Gradients in Battery Systems for Homogenous
Ageing of all the Battery Cells, thus Reducing the Need for Balancing
Sensorless Battery Cell Temperature Estimation, thus Enabling Safe and
Cost-Efficient Accurate Battery Pack Temperature Monitoring
Integration of Gas Sensors in Battery Systems for Early Fault Detection
and Improved System Safety
Power Antifuse as Low-Cost Device for Bypassing Faulty Battery Cells
Printed Temperature Sensor for Low-Cost Temperature Sensing to Improve
the Safety in Automotive Battery Systems
Page 26 Dr.-Ing. Vincent LORENTZ Division Power Electronics - Group Battery Systems © Fraunhofer IISB
Thank you for your attention For questions, do not hesistate to contact us:
Dr.-Ing. Vincent LORENTZ Group Manager Battery Systems;
Division Power Electronics
Fraunhofer IISB, Schottkystraße 10
D-91058 Erlangen, Germany
Telefon +49 9131 761-346