Development and Validation of a Thermal Simulation Model for Li-ion - - PowerPoint PPT Presentation

07.10.2011 Automotive Simulation Center e.V. 1

Development and Validation of a Thermal Simulation Model for Li-ion Batteries in HEVs/PEVs

Project Partners

• Dr. Ing Porsche, Adam Opel AG, Daimler AG

CD-adapco, Battery Design LLc

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Agenda

• Description of the Project
• Cell Level Modelling
• Thermal Modelling considerations
• Conclusion

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Description of the Project

Pictures and data courtesy of Behr

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Cell Level Modelling

• High Power Pouch Cell
• Temp range -100C to +400C
• Complete set of tests for 1 cell
• 8 cells tested at 1 point – 15C pulses at 300C
• Cell Model creation showed 2 effects for this cell

– Hysteresis within the OCV curves – Resistance does not follow an Arrhenius law

• Learning's for Activity

– Current must be zero during rest period – Chose the cell to be tested carefully – OCV measurements are critical – Extension of the RCR model

• RCR Tinterp

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Cell Level Modelling

Hysteresis Model Extension

• A real phenomena in cells
• Can be reduced by relaxing

the cell between measurements

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Cell Level Modelling

Hysteresis Model Extension Results using the hysteresis model, able to predict discharge and charge correctly

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Cell Level Modelling

Hysteresis Model Extension – Thermal Modelling Limited literature describing how to account for Hysteresis in thermal models

– Model uses average of both curves – Therefore total heat generation becomes Where

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Cell Level Modelling

Thermal Model Extension

• Model used an Arrhenius fit

– However cell exhibited 2 activation energies

• RCR Model Enhanced

– changed to use an interpolation method – Each temperature specific RCR model input – Interpolation as below

) (

1 1 2 1 2 1

T T T T OCV OCV OCV OCV              where T2>T>T1 20/03/2012

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Cell Level Modelling

Thermal Model Extension

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Consistency Checks on Whole Pack

• Pulse the pack and monitor the

cells response – Requires BMS for data – Issues with data capture

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Checks on Whole Pack #2

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1D Model 3D Models 2D Model 3D Model

• The plane of the current collectors is used to segment the model and produce a

distribution of current/potential within the entire cell

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Finite Volume Resolution Study

• A 2 battery cell model including the

conducting parts between was used

• This confirmed the appropriate

resolution

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Thermal Modelling of the Pack

• 2 approach's to modelling

the coolant channels

• 180 field functions added to

calculation, not 3D just variables

• Saving 2 -4 million FV cells
• Tabular inlet flow rate vs

time

Cooling Plate Model Tmax (C) Tmin (C) T

coolant_exit

(C) CPU Seconds With Coolant Flow

33.23 26.08 31.003 36.8

With1-D, Coolant Approx.

33.38 27.49 31.000 12.5 20/03/2012

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Thermal Modelling of the Pack

• Effect of the air flow developing in the battery pack and effect of radiation on the cell

temperature

• The natural convective heat transfer mode affects strongly the thermal heat balance inside the

battery and permits a heat exchange between the housing and the border cells

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• An extensive cell modelling/validation programme has

been discussed.

• Enhancements to the numerical models delivered.
• Items to consider in the complete pack model

presented.

• The final complete models are running at present.

Conclusions

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