1. 1 Electro-Thermal Analysis of Lithium Ion Batteries: Experimental and Numerical study Gad A. Pinhasi The Israeli Fuel Cell and Batteries Center (IFCBC) Conference 26 January 2011, Tel Aviv University

2. Outline The Objective The Project Background –Internal Resistance –Heat Generation The Study Experimental Setup –Calorimeter Models –Lumped heat model –CFC model Results –Cell –Battery –Pack 4 Conclusions Summery 2

3. 3 The Objective Thermal Analysis and Design of a Large Battery Pack. To evaluate the heat generation and temperature field under various electrical loads and design specifications. –Safety: Thermal Runaway –Max. Temperature restriction: –“Passive cooling” solutions

4. The Project Evaluation of Heat Generation: –Source term –Experimentally Calculation of the Temperature Field –Numerically Cell, Battery, Packs : 4, 92 4

5. Cell, Battery and Packs CellBatteryPack 4Pack 92 TypeICR18650 Samsung MR-2791YT-600 24 cells4 bat91(+1) bat 4S×6P4P7S×13P Voltage:[V]3.716.8 Capacity:[Ahr]2.614.457.6 Discharge currents [A]0.2, 0.4, 13, 4, 832 5

6. Introduction Evaluation of Heat Generation –Experimentally Calculation of the temperature field –Numerically Model Approaches Thermal characterization Battery Internal Resistance 6

7. Model Approaches Fundamental models physical foundations principles –Transport Phenomena 7 Phenomenological models Equivalent circuit models

8. Thermal characterization The heat produced due to: Joule heat of the electrical resistance Polarization heat Reaction heat –initially exothermic during discharge –reversible 8

9. Battery Internal Resistance The cell voltage under load is : –Open circuit voltage –Internal Ohmic resistance –“Concentration polarization” –“Charge transfer polarization” Methods for Determining the Internal Resistance –Ohm’s Law –Joule’s Law –AC Resistance –Electrochemical Impedance Spectroscopy (EIS) 9

10. Internal Resistance Dependence Temperature –Decreasing with Temperature State of Charge (SoC) State of Health (SoH) 10 Yurkovich et al. (2009)

11. 11 Internal Resistance and Heat Generation Joule heat of the electrical resistance Open circuit voltage

12. 12 The Study: Experimental and Numerical

13. Experimental Setup 13 Cell/ Battery/ Pack Liquid Bath Temperature Data logger Charge/ Load FLUKE: Data Acquisition Dewar: Calorimeter Load Charge Silicone Fluid Dow Corning DC ‑ 200/100 cSt

14. Batch / Continuous Flow (SHC) Calorimeter Calorimeter: 14 T w,in T w,out T oil,in

15. 15 Tools Numerical Study: Computational Fluid Dynamics (CFD) Partial differential equations (PDEs) solvers: –Fluid Mechanics –Heat Transfer –Mass Transfer (Diffusion) Chemical reactions COMSOL Multiphysics –Batteries & Fuel Cells Module ANSYS –CFX –FLUENT

16. The Lumped Model Cells Battery Medium Pack Medium Heat Transfer Mechanisms 16 Cell q”’q”’  24 Battery U 12 U 23 U3U3  91 q”’ T3T3 TT T2T2 T1T1

17. 17 Results Cell –Temperature history –Heat Generation and SOC Battery The Pack Electrical resistance –Open-circuit voltage –Heat Generation

18. Samsung 18650 ICR18650-26C 2600m Li-ion 3.7v Battery Brand :Samsung Nominal voltage : 3.7V Capacity: 2.6Ahr Size 18mm x 65.0mm Weight : 48g/pcs Made in JAPAN 18

19. 19 Cell Heat Generation and SOC 2.6A1A

20. 20 Pack 4 YT-600 4 Batteries 2791 4P Voltage: 16.8 Volts Capacity: 57.6Ahr

21. 21 Pack 4 Current: 32A Temperature –Battery inside –Battery Gap –Surrounding water Electrical voltage Electrical Power Heat Power zeros

22. 22 Pack 4: Simulation Experiment vs. Simulation Medium Effect: –air/oil

23. 23 Experiment vs. Simulation 0.6W/cell Simulation Experiment Points: Battery inside Battery Gap

24. 24 Experiment vs. Simple model Points: Battery inside Battery Gap 0.6W/cell

25. 25 Pack 4: Medium Effect: 32A 100min OilAir T max : 51ºC T max : 96ºC

26. 26 Summary The heat generation and temperature field for battery packs were evaluated theoretically and experimentally Internal resistance of a cell was determined by current step methods and thermal loss methods. Future Work: –Heat generation Correlation –Dynamic models –Fundamental models

27. People Dr. Gad Pinhasi –Department of Chemical Engineering and Biotechnology Dr. Alon Kuperman –Department of Electrical Engineering Neria Roth –(M.Sc. Student) Experimental Study Itshak Shtainbach –(M.Sc. Student) Numerical Study 27

28. Acknowledgment The research is supported by the ISRAEL Ministry of Defense : MAFAT

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31. 31 Conferences Roth, N., Shtainbach, T., Kuperman, A. and Pinhasi, G.A., "Electro-thermal Analysis of Lithium Ion Batteries: Experimental and Numerical study”, 1.The 31st Israeli Conference on Mechanical Engineering - ICME 2010, Dan Panorama Hotel, Tel- Aviv 2-3 June 2010. 2.The 47th annual meeting of the IIChE, 2010. The Israeli Fuel Cell and Batteries Center (IFCBC) Conference, 2011

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