Monitoring Cell Temperature to Optimize Battery Performance and Design Aida Rahim, PhD Senior Applications Engineer
Presenter Aida Rahim, PhD • Senior Applications Engineering • PhD Mechanical Engineering from MIT • Part of the Luna team since 2011 • Projects: • Temperature monitoring of battery packs • Embedding sensors in composites for structural testing • Supports: • Customer training and applications • Product testing
Luna Corporate Overview Founded 1990 NASDAQ: LUNA (2006) Edinburgh, Corporate HQ in Roanoke, VA United Kingdom TeraMetrix Division Luna Labs 260+ employees Ann Arbor, MI Stuttgart, Germany Charlottesville, VA Lausanne, Switzerland Beijing, China Headquarters - Roanoke, VA Worldwide presence and support Lightwave Division - Blacksburg, VA Guangzhou, China Shanghai, China - Atlanta, GA - Chino, CA Strong, consistent growth Corporate HQ Recent expansion Division HQ Commercial only ▪ Micron Optics – 2018 ▪ General Photonics – 2019
Luna Lightwave Division Focus Developing advanced optical technology that enable our customers to deliver better products and processes faster and more efficiently FIBER OPTIC SENSING OPTICAL MEASUREMENT & CONTROL Communications Test and Measurement Automotive | Aerospace |Structures | Security Sensing and gauging solutions that deliver data Innovative measurement technologies for testing and insight not available with conventional data optical components and networks deployed in telecom acquisition and monitoring systems and data-communications markets
Setting the Stage
Motivation A safer, more powerful, and cost-effective solution Sources: https://www.survivalkit.com/blog/how-to-deal-with-lithium-ion-battery-fires/ https://www.bestattorney.com/orange-county/hoverboard-injury-lawyers.html to detect and provide warning of battery faults well http://allaboutwindowsphone.com/flow/item/18407_Replaceable_batteries_again_ba.php https://www.scientificamerican.com/article/how-lithium-ion-batteries-grounded-the- in advance of failure is necessary dreamliner/ https://www.bensound.com/
Measurement Tool
Types of Fiber Optic Sensing Standard, Electrical Approach Multiple Copper Wires Per Sensor • 2-3+ wires per sensor • Multiple DAQs • Low resolution DAQ System • Bulky, metallic wiring Foil strain gages, Sensors thermocouples, RTDs, etc. Limited Data Susceptible to Bulky Sensors and Cabling (Low Sensor Count) Electromagnetic Interference Selected Sensor Locations
Types of Fiber Optic Sensing High-Speed Distributed Sensing • Single optical fiber Multiple Sensor Points Per Fiber FOS/FBG • Static and dynamic Interrogator measurements • Long range (km’s) • Easy to install High-Definition Distributed Sensing • Single optical fiber HD-FOS Distributed ‘Continuous’ • 1000’s of sensors Interrogator Measurements • Ultra-high spatial resolution • Easy to install
Fiber Optic Sensing Works in harshest Can measure where you Provides more data, environments need data more insight ▪ Very small, low profile ▪ High-definition mapping ▪ Passive (easy to embed) of strain/temperature ▪ Immune to EMI ▪ Lightweight ▪ Distributed sensing ▪ Chemically inert ▪ Flexible over large areas ▪ Intrinsically safe ▪ Distributed Optical Sensing can be applied at each level of battery design for all styles of cells
Types of Fiber Optic Sensing Single-Point Sensor Single sensing element • Fabry-Pérot Sensors Optical fiber • Single Fiber Bragg Grating Distributed Sensors Multiplexed/Quasi-Distributed Multiple sensing points • Fiber Bragg Gratings Optical fiber Fully Distributed • Rayleigh Continuous sensing along fiber • Raman Optical fiber • Brillouin
Fiber Bragg Grating (FBG) Sensing – How Does It Work? Fiber Bragg Gratings (FBGs) fiber core λ λ Transmitted Transmitted Signal Signal λ 1 λ 2 λ 3 Reflected Signal Reflected Signal Reflected Bragg wavelengths ( n ) change with strain and λ 1 λ 2 λ 3 λ temperature λ 1 λ 2 λ 3 λ
High-Speed FBG Sensing System Surface Strain Temperature Embedded Strain Acceleration ENLIGHT HYPERION (multiplexed Fabry-Perot) Measurement Software Interrogator Sensors Hundreds of sensors per system Strain, temperature, acceleration, displacement, etc. Acquisition rates up to 5 kHz HYPERION Long fiber range (km’s) Up to 16 parallel channels
Distributed Sensing: How it Works Optical Fiber Tunable Laser Source Rayleigh backscatter signal • Backscatter provides unique “fingerprint” of optical fiber Rayleigh backscatter, due to • Frequency shift correlates to change in applied strain or natural minute variations in temperature index of refraction in fiber core • OFDR system resolves shift along fiber length Strain or Temperature vs. Length 40 40 40 Temperature (°C) Temperature (°C) Temperature (°C) 20 20 20 0 0 0 -20 -20 -20 -40 -40 -40
High-Definition Fiber Optic Sensing System ODiSI HD Sensors – Strain and Temperature (Optical Distributed Sensor Interrogator) Measures strain or temperature continuously along fiber (resolution down to 0.65 mm) Sensor length up to 50 m (per channel) ODiSI Acquisition rates up to 250 Hz Up to 8 parallel channels
Comparing ODiSI and HYPERION High-Definition (Rayleigh) High-Speed (FBG/FP) Fiber Optic Sensing Fiber Optic Sensing Ultra-high spatial resolution High-speed measurements Measure continuously along standard FBGs or FBG/FP-based transducers optical fiber distributed on optical fiber Strain, Temperature, Strain, Temperature Acceleration, Displacement, Pressure ODiSI HYPERION
DEMO High-Definition Fiber Optic Sensing with Luna ODiSI 6100
Application to Batteries
Effective and Efficient Design Tool Cell Monitor the temperature ▪ Evaluate effects different charge/discharge of every terminal with rates have on cell chemistry one sensor ▪ Qualify cells being cycled in different environmental conditions Module Enclosure ▪ Evaluate cooling effectiveness ▪ Find hot-spots among clusters of neighboring cells Pack Cells ▪ Ensure cell connections are robust ▪ Evaluate thermal profile inside enclosures https://www.electricvehiclesresearch.com/articles/2822 /the-growing-ev-market-will-fail-without-battery-size- standards-support Optical Sensing can be applied at each level of battery design for all cell types.
Integrating fiber sensing into a battery Directly on the terminals ▪ Sensor can be placed across each Fiber Sensor path covering terminal every terminal on a module ▪ Held in place with a putty, tape, or other non-conductive material Using a pre- made “pad” design ▪ Sensor is fabricated into electrically non-conductive sheet ▪ Pattern ensures proper placement ▪ Simplifies installation Pre-fabricated sheet integrated Fiber Path into a simulated battery module
Battery Fault Monitoring: Temperature Cell 1
Battery Fault Monitoring: Strain
Design and Evaluation of a 1000V Li-Ion Battery High voltage energy storage Understand the safety and reliability challenges 1000 VDC lithium-ion cell battery at University of Texas Arlington, instrumented with a single fiber sensor A single 10S/1P LI module 1000 VDC LFP-LI battery During installation, the location of each terminal throughout the 280S/1P battery was saved as a location of interest Fiber Sensor path covering every terminal on a module Monitor the controlled cycling of the battery to characterize its performance Dodson, David A.; Wetz, David A.; Sanchez, Jacob L.; Gnegy-Davidson, Clint; Martin, Matthew J.; Adams, Blake; Johnston, Alexander; Heinzel, John; Cummings, Steve; Frank, Nick; Rahim, Nur Aida Abdul; Davis, Matthew, Design and Evaluation of a 1000 V Lithium-Ion Battery. Naval Engineers Journal, Volume 131, Number 3, 1 September 2019, pp. 107-119(13)
Design and Evaluation of a 1000v Li-Ion Battery 250kW discharge, 5s ON/1s OFF pulsed profile Temperature increase of each cell is similar Module 13 cell temperatures vary widely: 45ºC to 75ºC Possible reasons: ▪ Higher ohmic contact resistance between the cell terminal and the bus bar interconnecting series cells Individual cell temperatures ▪ Poor thermal contact at the cell terminals If higher ohmic loss, this location needs to be assessed more carefully prior to use When this type of thermal resolution is not captured, these potential issues of concern are never identified Dodson, David A.; Wetz, David A.; Sanchez, Jacob L.; Gnegy-Davidson, Clint; Martin, Matthew J.; Adams, Blake; Johnston, Alexander; Surface plots of Module 8 and 13 Heinzel, John; Cummings, Steve; Frank, Nick; Rahim, Nur Aida Abdul; Davis, Matthew, Design and Evaluation of a 1000 V Lithium-Ion Battery. Naval Engineers Journal, Volume 131, Number 3, 1 September 2019, pp. 107-119(13)
“What if?” Application Envision an electric vehicle which has a sensor integrated into its battery and that sensor is used to monitor battery temperature during charging. Data is provided to the charging station enabling active control of the charge rate. Could the time to full charge be reduced if every cell temperature was monitored? Would battery life be increased if the control method took into account cell temperature when charging? https://hawaiienergy.com/for-businesses/incentives/electric-vehicle-charging-stations
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