NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC. e Alliance for Sustainable Energy, LLC. 

Comparison of Battery Life Across 

Real-World Automotive Drive-Cycles 

7th Lithium Battery Power Conference 

Las Vegas, NV 

Kandler Smith, Matthew Earleywine, 

Eric Wood, Ahmad Pesaran 

November 7-8, 2011 

NREL/PR-5400-53470 
 

Motivation
 

•	 Overcome barriers to clean, efficient 

transportation 

o	 Electric-drive vehicles 

•	 Maximize life, minimize cost of electric 

drive vehicle batteries (alt: maximize 

income) 

•	 Quantify systems-level tradeoffs for 

plug-in hybrid vehicle (PHEV) batteries 

o	 3000-5000 deep cycles 

o	 10-15 year calendar life at 35°C 

o	 $300/kWh at pack level
 

(2014 target ~ 70% reduction)
 

2
 
 

 

 

 

 

 

 

DOE’s Computer-Aided Engineering of Batteries (CAEBAT) 

Program Integrating Battery R&D Models 

Physics of Li-Ion Battery Systems in Different Length Scales 

Li diffusion in solid phase 

Interface physics 

Particle deformation & fatigue 

Structural stability 

Charge balance and transport 

Electrical network in 

composite electrodes 

Li transport in electrolyte 

phase 

Electronic potential & 

current distribution 

Heat generation and 

transfer 

Electrolyte wetting 

Pressure distribution 

Atomic Scale 

Particle Scale 

Electrode Scale Cell Scale 

System Scale 

System operating 

conditions 

Environmental conditions 

Control strategy 

Module Scale 

Thermal/electrical 

inter-cell configuration 

Thermal management 

Safety control 

Thermodynamic properties 

Lattice stability 

Material-level kinetic barrier 

Transport properties 

Challenge: How to perform life-predictive analysis for “what-if” 

scenarios untested in the laboratory (V2G, charging behavior, swapping, 2nd use, ...) 

3
 
 

 

 

 

Factors in Vehicle Battery Aging
 

Cell Design Environment Duty Cycle 

• Chemical 

• Electrochemical 

• Electrical 

• Manuf. uniformity 

o defects 

• Thermal 

o geography 

o thermal management 

system ($) 

o heat generation 

• Humidity 

• Vibration 

• System design 

o vehicle 

o excess power & 

energy @ BOL ($) 

o system controls 

• Driver 

o annual mileage 

o trips/day 

o aggressiveness 

o charging behavior 

– charges/day 

– fast charge 

4
 
 

 

 

 

Factors in Vehicle Battery Aging
 

• Chemical 

• Electrochemical 

• Electrical 

• Manuf. uniformity 

o defects 

• Thermal 

o geography 

o thermal management 

system ($) 

o heat generation 

• Humidity 

• Vibration 

Cell Design Environment 

• System design 

o vehicle 

o excess power & 

energy @ BOL ($) 

o system controls 

• Driver 

o annual mileage 

o trips/day 

o aggressiveness 

o charging behavior 

– charges/day 

– fast charge 

Duty Cycle 

(Not considered) 

5
 
 

 

Simulation Approach 

Vehicle drive cycles 

• 782 speed vs. time traces 

• Charging assumptions 

Battery power profile 

• SOC(t), Heat gen(t), etc. 

Vehicle 

Model e.g., Cyc_4378_1 

PHEV10 Opp. Chg 

6
 
 

 

 

Simulation Approach 

Vehicle drive cycles 

• 782 speed vs. time traces 

• Charging assumptions 

Battery stress statistics Battery T(t), Voc(t), ∆DODi, Ni, ... 

Thermal 

Model 

Vehicle 

Model •

Battery power profile 

• SOC(t), Heat gen(t), etc. 

• Thermal management assumptions 

7
 
 

 

 

Simulation Approach 

Vehicle drive cycles 

• 782 speed vs. time traces 

• Charging assumptions 

Years 

Battery Life 

Model 

Battery 

Thermal 

Model 

Vehicle 

Model 

15 C 

20 C 

30 C 25 C 

10 C 

Minneapolis 

Houston 

Phoenix 

Capacity 

NCA/Graphite 

Life 

Battery stress statistics 

• T(t), Voc(t), ∆DODi, Ni, ... 

Battery power profile 

• SOC(t), Heat gen(t), etc. 

• Thermal management assumptions 

8
 
 

 

 

 

 

 

Life Model Approach 

Battery aging datasets fit with empirical, yet physically justifiable formulas 

Relative 

Resistance 

Relative 

Capacity 

Qactive = e0 + e1 N 

R = a1 t1/2 + a2 N 

Calendar fade 

• SEI growth (partially 

suppressed by cycling) 

• Loss of cyclable lithium 

• a1, d1 = f(∆DOD,T,Voc) 

Q = min ( QLi , Qactive ) 

QLi = d0 + d1 t1/2 

Cycling fade 

• active material structure 

degradation and 

mechanical fracture 

• a2, e1 = f(∆DOD,T,Voc) 

Enables life predictions for untested real-world scenarios 

9
 
Acceleration Factors

  1 

assumed mu

• Tafel Eqn.

F

 T

V



  









  





a

  









• Arrhenius Eqn. • Describe a1, 

• Combined ef

f(T,Voc,ΔDoD

T(t) Tref

Voc (t) Vref

T(t) Tref

E 1

• Wöhler Eqn.

DoD

R

R

exp

exp

 

DoD DoDref
Acceleration Factors

Resistance growt

• Arrhenius Eqn.

 T

 

   1  



a

• Tafel Eqn.

F V

  





  









T(t) Tref

Voc (t) Vref

T(t) Tref

• Wöhler Eqn.

DoD

E 1

R

R

exp

exp

DoD DoDref

 
Acceleration Factors

Resistance growt

• Arrhenius Eqn.

 T



  

 1   

   



  a  

• Tafel Eqn.

F V   

  

T(t) Tref

Voc (t) Vref

T(t) Tref

• Wöhler Eqn.

DoD

E 1

R

R

exp

exp

DoD DoDref

 
Acceleration Factors

Capacity fad

• Arrhenius Eqn.

 T







   1

 





  



• Tafel Eqn.

F V

 a





  







T(t) Tref

Voc (t) Vref

T(t) Tref

• Wöhler Eqn.

DoD

E 1

R

R

exp

exp

DoD DoDref

 
3

Vehicle & Battery Assumptions

80% 

11.48 

48 

PHEV10 PHEV40 

All-electric range, km 16.7 67 Total vehicle mass, kg 1714 1830 Electric motor power, kW 40 43 IC engine power, kW 77 80 Useable power, kW 44 Useable energy, kWh 2.67 Maximum SOC 90% Minimum SOC at BOL 30% 30% Minimum SOC at EOL 13% 10% Excess energy at BOL 100% 67% Excess power at BOL, 10% SOC 43% 43% Heat transfer area - cells-to-coolant, m2 1 3 

Heat transfer area - pack-to-ambient, m2 1.2 2.9 

Heat transfer coeff. - pack-to-ambient, W/m2K 2 2 

Battery 

Thermal2, 

Battery 

Electrical1 

Vehicle 

1. EOL condition = 75% of BOL nameplate 1C capacity remaining 

2. Heat generation rate at 2/3 of EOL resistance growth 
** 

* Worst‐case hot climate, P

Life Variability with Real‐World Dri

Thermal Management2 • Fixed 28oC battery temperature* 

• Limited cooling (forced ambient air) • Aggressive cooling (20oC chilled liquid) 

Charging 

• Nightly cha• Opportunity 

Drive Cycle

• 782 Real-World d

cycles from Texas of Transportation 

Vehicles 

• PHEV10 sedan • PHEV40 sedan 

• Matrix of analytic scenarios

Average daily driving distance of Texas dataset is 37.97 miles/day. This paper assumes 335 driving days and 30 rest days per ye

equivalent average mileage of 12,375 miles/year. 5 th and 95th percentile daily driving distances from the Texas dataset are 99.13 

2. A constant ambient temperature of 28oC was assumed for all thermal simulations, representative of typical worst-case hot climat

conditions, this effective ambient temperature causes similar battery degradation as would daily and annual temperature variation

3. Charging at Level I rate of 1.5 kW. 1. 
Results

• Variability in PHEV battery life 

real‐world drive cycles

• Impact of thermal manageme

• Impact of opportunity versus 

charging
Expected Life – PHEV10

Nightly ChargePhoenix ClimateConstant 28oC

• Different daily driving distances and battery c

histories result in a distribution of expected b

• Here, life 

782 drivclimate i

• Key assu

o Grapo End‐

75% (of i

o 80% o 30% 

OppV2G
Expected Life – PHEV10 vs. PHEV4

Nightly ChargePhoenix ClimateConstant 28oC

86% of driving

cycles > 10 mi/day34% of driving

cycles > 40 mi/day
Three battery thermal management 

illustrated for an example driving 

e.g

Oppo

Driving State Battery Temperature

(time shown here is initialized to start of first driving trip of the day)

(forced 

(baseline cas

2) Lim

1) Isothe
Expected Life – Thermal Manageme

Limited Cooling Scenario(Tfluid=28°C, h=15 W/m2K)• • Excessive temperature rise

shortens life by 1‐2 yearscompared to baseline

Aggressive Cooling Scenario(Tfluid=20°C, h=85 W/m2K)• • Periodic drawdown of

battery temperature to20°C, possible during

charging with chilled

coolant, extends life by 1‐3

years compared to baseline

Isothermal

Limited

Aggressive

PHEV10 

Error bars denote 5th and 95th p
Impact of Opportunity Charging (L

PHEV10 PHEV

• PHEV10: Frequent charging can • PHEV40: Frequen

reduce average life by 1 year extend average li
Cyc_4378_1

Impact of Opportunity Charging (L

Shallower Deeper

cycling cycling

Longer life

Shorter life

PHEVLong

shalloPHEVGeneto ma

• • 
Life‐Extending Controls

Drive cycle comparison

Heat gen rate Cyclic‐thro

Controls

• Thermal

management system

• Allowable power

• Allowable energ

• Warranty

o Years lifeo Miles or kilo

• Allowable charge

+ environment + charging 
Opportunity for Life‐Controls – PH

Regat y

by 

• R

dab

• R

b

• L

0
Conclusions

• Electric‐drive vehicle batteries designed to la

under worst‐case duty cycles and environme

well beyond that for typical aging conditions

o Opportunities for vehicle‐to‐grid and 2nd use

• Refrigeration‐type cooling systems reduce ex

over‐sizing of batteries specifically for hot cli

• Worst‐case PHEV driving and charging patter

with high utilization of charge‐depletion mod

operation

o Small PHEV10 battery life highly sensitive to freq

scenarios for moderate‐to‐high mileage drivers

o However, electricity is less expensive than petro

operation and can financially offset shorter batt

o Opportunities to improve life through design an
Acknowledgments

• DOE Office of Vehicle Technologies

o Dave Howello Brian Cunningham

• Data and Research Support

o Loïc Gaillac, Naum Pinsky – S. California o John Hall – Boeingo Marshall Smart – NASA

‐Jet Propulsion