Challenges in battery pack design for electric vehicles ......Challenges in battery pack design for...
Transcript of Challenges in battery pack design for electric vehicles ......Challenges in battery pack design for...
Challenges in battery pack design for electric vehicles with special emphasis on
state-of-charge (SOC) estimation
by Dr. Angelique Janse van Rensburg, North-West University
Overview
• Introduction
• Battery packs
• State-of-charge (SOC)
• Electromotive force (EMF)
• Electrolyte concentration
• Conclusion
https://cleantechnica.com/2017/04/11/panasonic-hints-beyond-lithium-technology-ev-battery-improvements/
http://lygte-info.dk/info/batteryDisassembly5000mAh%20UK.html
Electric vehicle technology
• 2 million EVs on road (2017)
• 0.2% of light-duty passenger vehicles
• Adoption barrier: purchase cost
– Improvements in mass production
– Tax exemptions
• Major adoption barrier for BEV
• ‘Fuel gauging’
• Accurate SOC information for consumer
• Battery management system (BMS) performance + lifetime
• Batteries currently in EVs ≈ 100 GWh
• Managed safely + reliably for performance
Introduction⇛ Battery Pack ⇛ SOC ⇛ EMF ⇛ Concentration ⇛ Conclusion
RANGE
Battery energy storage in electric vehicles
• Battery pack = entire battery energy storage system
http://www.hybridcars.com/chevy-bolt-evs-battery-is-as-big-as-a-teslas/
wiring
Introduction⇛ Battery Pack ⇛ SOC ⇛ EMF ⇛ Concentration ⇛ Conclusion
sensors
switches
ICs
BMS
TMS
holders
tubing
connectors
casings
MSCELLS
Measured voltage of 18650 lithium-ion cell
Introduction⇛ Battery Pack ⇛ SOC⇛ EMF ⇛ Concentration ⇛ Conclusion
100%
0%
100%
intR
Capacity and state-of-charge (SOC)
Introduction⇛ Battery Pack ⇛ SOC⇛ EMF ⇛ Concentration ⇛ Conclusion
• How long can ion transport and electron transfer continue to sustain observed current within voltage range?
= depletion active material / ion concentration, passivation
Observed current from main reaction
Introduction⇛ Battery Pack ⇛ SOC⇛ EMF ⇛ Concentration ⇛ Conclusion
Discharging:
Electrochemical double-layer
REDOX
Maximum work possible by a cell
Introduction ⇛ Battery Pack ⇛ SOC ⇛ EMF⇛ Concentration ⇛ Conclusion
EMF – SOC
The Nernst equation
Introduction ⇛ Battery Pack ⇛ SOC ⇛ EMF⇛ Concentration ⇛ Conclusion
EMF – Concentration
( )Q f m
concentrationm
• Validated model in COMSOL Multiphysics:
Concentration in lead-acid cell during discharge
Introduction ⇛ Battery Pack ⇛ SOC ⇛ EMF ⇛ Concentration⇛ Conclusion
Work, electromotive force and concentration
Introduction ⇛ Battery Pack ⇛ SOC ⇛ EMF ⇛ Concentration⇛ Conclusion
maxw nFE
inttE V I R
ln ( )RT
E E f mnF
, at resttE V E
at restm
during operationw
Measurements/estimates:Equations:
Mapping concentration to work done
Introduction ⇛ Battery Pack ⇛ SOC ⇛ EMF ⇛ Concentration⇛ Conclusion
( )E m
Electrolyte concentration for EMF characterization
• Experimental result for VRLA cell with AGM separator:
Introduction ⇛ Battery Pack ⇛ SOC ⇛ EMF ⇛ Concentration⇛ Conclusion
Final thoughts
Introduction ⇛ Battery Pack ⇛ SOC ⇛ EMF ⇛ Concentration ⇛ Conclusion
Final thoughts
• Understanding of smallest unit
• Meaning behind capacity
• Improve SOC estimation
• Address challenges increase safety, reliability and performance
• Advances in fundamental research
• Accelerate EV adoption
Power of battery energy storage
Enabling EV as disruptive technology
Introduction ⇛ Battery Pack ⇛ SOC ⇛ EMF ⇛ Concentration ⇛ Conclusion
Questions?
Dr. Angelique Janse van RensburgSenior Lecturer in Computer & Electronic Engineering
Unit for Energy and Technology SystemsFaculty of Engineering, North-West University
Potchefstroom, South Africa