The trouble with batteries:
Modelling electrochemical systems in a vehicle
Dr. Chris Lyness
Jaguar Landrover
Battery Cell Technical Specialist
Light Vehicle Fleet CO2 Targets
• Global CO2 emission
targets are becoming more
stringent
• A range of strategies are
required to achieve the fleet
average targets
• The electrified power train
is the only credible zero
emissions solution
Why Batteries?
Technology Introduction
Why Do We Need Different batteries?
MHEV
(Micro hybrid)
Charge from braking
Provide 48V power to
auxiliaries
Limited Motor assist
High power required
V. Low energy
storage
Only a small amount
of the cells ability
exploited
~11Kg
~15L
~0.5KWh
~>11kW peak
Nominal voltage: 42V
Peak current -230A
Low Cost, Low Impact
HEV
Charge from
braking
Motor assist
Limited EV driving
High power
required
Low energy
storage
Only a small
amount of the cells
ability
exploited
~50Kg
~50L
~1.5KWh
~>43kW peak
Nominal voltage: 260V
Peak current -180A
PHEV
BEV
Charge from the
plug
Charge from
braking
Motor assist
EV driving
High power
required
High energy
storage
Full cell capability
exploited
Charge from the
plug
Charge from
braking
EV driving
High power
required
High energy
storage
Full cell capability
exploited
~185Kg
~150L
~15KWh
~>130kW peak
Nominal Voltage:370V
Peak current -300A
~550Kg
~350L
~70KWh
~>290kW peak
Nominal Voltage:356V
Peak current -1000A
High Cost, High Impact
Improving Battery Performance
Improving Battery Performance
Cell
Module
Pack
X~100
X12
22 kWh
Aerodynamically optimised EV
~300 kg
Active
Material
~48Kg
Example:100 mile range
Battery Design Choices
How does the Micro affect the Macro?
Cell Material
Failure Trigger
Pack containment
High Voltage wiring harness
High voltage isolation system
Heating system?
Mechanical Harness
Packaging
Cooling system
Low voltage wiring harness
Electronic control modules
Cell
Fixed costs, Warranty, Profit
Key Battery metrics
8.3MWh
Small Nuclear
Power station
Key Battery metrics
8.3MWh
Small Nuclear
Power station
Vehicle System Challenges
Time domains
Electron transfer
Charge transfer
Diffusion
SEI
System Noise
Drive Cycle
Battery Degradation
10-9
10-3
10-6
100
103
106
109
Seconds
Dimensions
Material Properties
Materials Design Electrode Architecture
Transport properties
Transport paths
Surface effects
Cell system architecture
Surface area
Interface
Particle size
Layer thickness
Porosity, totuosity
Cell
Battery
Vehicle
10-10
10-8
10-6
10-4
10-2
10-0
Metre
Electro-Thermal Model Requirements
Voltage
Initial Conditions
𝑇0 , 𝑆𝑂𝐶0
Drive Cycle
Cell
Model
SOC
Temperature &
Heat
Requirements
• Spatially resolved(thermally)
• Model outputs correct to less than 2% error
• Valid in temperature range -40 ≤ T ≤ 60
• Cells in a pack are uniquely parameterisable
• Paramatised within 2-3 months
• Runs close to real time
System Model Context
Driver
Vehicle
Battery
Battery
Signal
Battery
Power
Electrical Modelling Approaches
Basic
Equivalent Circuit
Electrochemical
P=I.Vocv+ I2.R
Analogy
Phenomenological
Mechanistic
Characterisation time
1 Day-1week
Characterisation time
1 week-1 month
Characterisation time
6 months -1 year
Run time: <real time
Run time: <real time
Run time: >real time
Tanvir R. Tanim, Christopher D. Rahn (2015 Journal of
Power Sources, Volume 294, Pages 239-247
Characterisation requirements
Basic
Electrochemical
Equivalent Circuit
[5]
Incremental Capacity
[3]
SEM imaging
Pulse Power
[4]
Volatge [V]
4.5
4
3.5
3
2.5
0
20
40
Time [mins]
60
Tomography
EIS Tests
Constant Discharge
[3]
[4]
[5]
Y. Li et. al., "Mesoporous Co3O4 nanowire arrays for lithium ion batteries with high capacity and rate capability." Nano Letters 8.1 (2008): 265-270.
M. Ebner, Laboratory for Nanoelectronics, ETH Zurich
C. Pastor-Fernández , K. Uddin, J. Marco, WMG, University of Warwick
A Problem of Validation
Time Domains
Validation
Focus
Electron transfer
Charge transfer
Diffusion
SEI
System Noise
Drive Cycle
Battery Degradation
10-9
10-6
10-3
100
103
106
109
Seconds
The Changing nature of modelling
requirements
Time
BEV
?
Domains
Energy Cell
PHEV
Cell
Diffusion
sensitivity
HEV
Power Cell
Electron transfer
Charge transfer
Diffusion
SEI
System Noise
Drive Cycle
Battery Degradation
10-9
10-6
10-3
100
103
106
109
Seconds
What next?
• Vehicle system modelling has to become more sophisticated
• Better understanding of battery fundamental mechanisms is
crucial
• Increasing focus on ground up modelling of battery systems
But….
• The Challenges is not just in building the model
• Rapid characterisation & run speed are crucial for wide stream uptake
Thankyou