Modeling of Battery Systems and Installations for Automotive Applications

Transcription

1 Modeling of Battery Systems and Installations for Automotive Applications Richard Johns, Automotive Director, CD-adapco Robert Spotnitz, President, Battery Design

2 Predicted Growth in HEV/EV Vehicles Source: Hiedge

3 Typical HEV Battery Installation Picture A123 3

4 HEV Battery Installation Picture Daimler 4

5 EV Battery Installation Cooling Outlets 5

6 EV Battery Installation Cooling Outlets 6

7 Issues to be Addressed Li-ion batteries offer the most likely route to HEVs and EVs and are being actively pursued by most OEMs However, there are many issues to be resolved: Cost, Lifetime, Durability, Safety Rapidly developing battery technology Many of the important technical problems incl. Lifetime, Durability, Safety, are related to high temperatures and thermal management is one of the critical issues to be resolved CD-adapco and Battery Design LLC are investing heavily to have the right software tools available for the analysis of battery pack and vehicle installations 7

8 ) ( condenser radiator Thermal Management: Cooling Strategies Air cooling Liquid cooling 2 Refrigerant Chiller TXV Pump Battery 6 Air Evaporator Coolant circuit Battery E-compressor 5 8

9 Battery cooling of various cells types 9 Source: Behr

10 Typical cell internal construction details 10 Source: Behr

11 Thermal Management Load cases: Drive-Cycle P elec (W) Hot soak High-rate charging t(s) Cold start Assessment Criteria: T uniformity (Δ < 3 C) T op ~ 35 C, T max < 55 C Cooling system parasitic losses Safety thermal runaway Source: NREL

12 CD-adapco and Battery Design LLC Partnership CD-adapco and Bob Spotnitz, one of the world s foremost battery system modelers and President of Battery Design LLC, have formed a partnership to develop a full flow-thermal-electrochemistry capability in STAR at the cell, pack and installation levels Installation Pack Picture Behr Cell 12

13 CD-adapco and Battery Design LLC Partnership Battery Design LLC: Detailed modeling of the cell electro-chemistry CD-adapco: Detailed 3D modeling of the flow, thermal and stress The Partnership will deliver a transient, fully-coupled simultaneous solution of the flow-thermal-electrochemistry 13

14 STAR-CCM+: Total Vehicle Thermal Protection Extensive validation has been carried out in many areas

15 Cell Models It is NOT possible to predict cell performance solely from design data There are 2 levels of complexity for modeling cell behaviour: 1) Simple Circuit Model: Experimental data is used to determine the coefficients of a curve fit over a range of battery operating condition. This model is recommended for thermal studies within the range of fitting. 2) ElectroChemistry Model: A detailed model of the cell physics. Requires both experimental data AND detailed knowledge of the cell design. This model would be necessary to predict behaviour beyond the range of the experimental data (eg thermal runaway) or for extended physics models (eg Li plating) Identical cell models are implemented in STAR-CCM+ and Battery Design Studio used to set up the parameters of the model 15

16 Battery Design LLC Software for Battery Design and Simulation Battery Design Studio the means to model batteries To analyze data To visualize cell designs To compare experiments with models To visualize model results Database Development started April 1999 User Input Output Lab Models Data Size Cost Power Impedance Life Abuse, etc 16

17 Simple Circuit Model Example shows level of fit with experimental data for a discharge/charge cycle Five parameters OCV, OCV, R o, R p, C Page 17 17

18 Unit Cell Electrochemistry Model 18

19 Enhancements to the standard model Coupled to sizing programs in Battery Design Studio all geometry information set up automatically Temperature and concentration dependent solid-phase diffusion coefficients important for accuracy over a wide range of conditions Multiple active materials common feature of many contemporary design of batteries Side reactions (lithium deposition component of ageing, self discharge) Choice of kinetics expressions (linear, Tafel, Butler Volmer)

20 Electrochemistry model Example shows level of fit with experimental data for a discharge/charge cycle Example shows comparison between measurements and simulation for a HPPC (High Pulse Power Characterization) Test Cycle 1 Cycle 9

21 Electrochemistry model Example shows level of fit with experimental data for a discharge/charge cycle Example shows comparison between measurements and simulation for a C/5 discharge > charge > C/2 discharge > charge > C discharge > charge > 2C discharge cycle 21

22 Coupled Flow-Thermal-Electrochemistry solution process All cell models simple circuit to full electrochemistry are available in STAR-CCM+ The electrochemistry models used in STAR-CCM+ and Battery Design Studio are identical BDS is used to set up the cell characterization, given the cell measurement and design data. The output is the TBM file Simple circuit cell models are relatively straightforward to set up and users can be easily trained to do this Full electrochemistry models are more complicated to set up and require assistance from Battery Design LLC The STAR-CCM+ solution is fully coupled at time-step level between the flow, thermal and electrochemistry models 22

23 Electrical Model Battery and cell electrical connections and current flows are included in the model. Cell mapping (far right) shows discretisation of a prismatic cell to allow for spatial variations within a cell 23

24 The Engineering Process Boundary Conditions CFD Knowledge Battery design Cell design Build CFD Model STAR-CCM+ TBM File Solver & Postprocessing STAR-CCM+ Cell measurements Cell Characterization BDS Li-ion cell knowledge Li-ion cell & CFD knowledge 24

25 Summary All major auto OEMs have programs for electric vehicles for a rapidly growing worldwide market Battery technology is a key enabler and differentiator BUT thermal issues strongly influence lifetime, durability and safety CD-adapco and Battery Design LLC have formed a partnership to jointly develop a coupled flow-thermal-electrochemistry solution for cell, pack and installation level simulation This new capability will be available in STAR-CCM+ June