European GT Conference - gtisoft.com€¦ · Agenda 02.10.2019 01 Introduction Cell Calibration...

Evaluation of the Thermal Behavior of a 48V EV Battery with Passive Cooling

European GT Conference

M.Sc. Dennis Schier / Dr.-Ing. Frank Seifert

Frankfurt, October 2019

2© Rheinmetall Automotive AG I

Agenda

02.10.2019

Introduction01

Cell Calibration with GT-AutoLion

Thermal Model of the Battery Pack03

02

Results04

Conclusion05

GT Conference 2019 – Evaluation of the Thermal Behavior of a 48V EV Battery with Passive Cooling


Introduction

• Rheinmetall Automotive is traditionally strong in the market of conventional drive trains

• Expansion of the traditional product portfolio with products for electric and hybrid drive trains

• become a competent partner for electric drives, battery packs and power electronics

Motivation:

• Development of a simple tool for the evaluation of (scalable) battery pack concepts

• Fast reaction for customer inquiries

Requirements:

• Low calibration effort based on 3D CFD

• Cell Temperature error should not exceed 1K on average

• Gradient of the individual cell temperatures across the battery pack must be consistent


02.10.2019


Calibration for stationary

Cell Temperature Distribution

Simulation Workflow


Geometry

Preprocessing

Geometry Translation into

Thermal Masses Model

Model Parametrization

for Thermal Distances

Cell Calibration

� Comparison of stationary and transient results with 3D CFD

� Comparison of cell model with test results

� Validation with test results

� Calculation of temperature distribution for real drive cycles

02.10.2019


Agenda

02.10.2019

Introduction01



02

Results04

Conclusion05



GT-AutoLion | Cell Description


Cell Characteristics:

• Prismatic Cell

• Stacked Electrodes

• LiFePO4 / Graphite

• 72 Ah Capacity

• 3.2V Nominal Voltage

• 2C max. Constant

Current

Create AutoLion model to simulate cell behaviour:

Available Data for model creation and calibration:

• CT-Scan

• Official Datasheet

• Capacity Test for 0.05C (Discharge)

• Capacity Test for 1/3C, 1C and 2C (Discharge)

Electrical Data

Thermal Data

Model

02.10.2019


GT-AutoLion Template

Cell Dynamics Calibration

Optimization

OCV Calibration

GT-AutoLion | Calibration Workflow


CT-Scan Official Datasheet

Capacity Tests for 0.05C

Capacity Tests for 1/3C, 1C and 2C

• Geometry Parameters

• Capacity Loading | N/P Ratio

• First Charge/Discharge Capacity

• OCV@100% SOC

• Contact Resistance

• Diffusivity Multiplier

• Heat Transfer Coefficient

GT-AutoLion Template Parameters

02.10.2019


GT-AutoLion | Calibration Results


• Calibration results for capacity discharge tests

OCV|1/3C|1C|2C

• Maximum error about 1% for voltage values

• Capacity fit for all cases (except 2C)

• No calibration of charging tests so far

� Template can be integrated into complete Battery

System Model

� Heat flow from cells can be extracted and fed into

Thermal Model

02.10.2019


Agenda

02.10.2019

Introduction01



02

Results04

Conclusion05



Profile � Aluminum

Cell Fixing - Plastic

Profile

�Caoutchouc

Thermal Model (TM) | Battery Setup


Prismatic Cell

� Lithium Ion

Case � Aluminum

• 48 Volt Application

• Battery Capacity 15kW-h

• Two chambers (symmetrical)

• 64 prismatic battery cells

• Passive cooling

Backfilling

Material

(Compound) �

Synthetic Resin

Busbar � Copper

02.10.2019


TM| Geometry Preparation and Modelling


• Preparation of the CAD geometry in SpaceClaim

• Simplification of the CAD model

• Definition of a thermal resistance between the cells instead of a thermal

mass for the casting compound

• Consideration of the anisotropy of the battery cell

• Control of the heat flows in the battery pack

Sectioning of the casting compound into

5 thermal masses1 2

3

4

5

02.10.2019

Intermediate

material

• Anisotropic

material properties

• Coordinate

direction

Thermal resistance between all cells

λλλλ

Thermal

conductivity

xy

z


TM| Battery Pack with Thermal Masses


One Chamber of the Battery Pack

Battery Cell

Case

Air

Volume

Ambient

Conditions

Cover Plate

02.10.2019

Part of the

Backfilling

Material

Busbar126 thermal masses

Model with nearly 1000 possible

calibration Parameter for “DtMC”

Optimization:

17 Parameter for “DtMC” in use

to keep it “as simple as possible”

“DtMC”: Distance to Mass Center

CFD Analysis


8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1

37.3 37.7 37.9 38.0 38.0 38.0 37.9 37.6 4 37.4 37.7 37.8 37.9 38.0 37.9 37.9 37.6 4

37.6 38.1 38.4 38.5 38.6 38.5 38.3 38.0 3 37.6 38.1 38.4 38.5 38.5 38.4 38.3 37.9 3

37.7 38.1 38.4 38.5 38.5 38.5 38.3 37.9 2 37.6 38.1 38.4 38.5 38.5 38.4 38.3 37.9 2

37.4 37.7 37.9 38.0 38.0 38.0 37.9 37.6 1 37.4 37.8 37.9 38.0 37.9 37.9 37.8 37.6 1

left side of the battery pack - 3D CFD Simulation left side of the battery pack - GT-Suite Simulation

TM | Model Calibration


• Calibration of stationary load points with results from 3D CFD

for different cases

• Variation of stationary cell heat source

• Variation of stationary ambient conditions

• Optimization for “Case Sweep and Cross-Case Studies”

• Goal: average cell temperature calibration error ≤ 1K

• Result: max. ave. error about 0.25K / symmetry between chambers

• Transient results for a 7-Day-Cycle with calibrated model

• Changing BC´s for HTC, temperature and heat source

02.10.2019

8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1

37.4 38.1 38.4 38.6 38.6 38.5 38.3 37.8 4 37.5 38.2 38.5 38.6 38.8 38.7 38.5 38.0 4

37.9 38.8 39.3 39.5 39.5 39.4 39.1 38.3 3 38.1 39.1 39.5 39.7 39.8 39.7 39.3 38.6 3

37.9 38.8 39.2 39.4 39.5 39.4 39.0 38.2 2 38.1 39.1 39.5 39.7 39.8 39.7 39.3 38.6 2

37.4 38.1 38.4 38.5 38.6 38.5 38.2 37.6 1 37.6 38.3 38.6 38.7 38.7 38.6 38.4 38.0 1


8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1

44.4 45.9 46.6 47.0 47.0 47.0 46.6 45.5 4 44.6 46.0 46.6 46.9 47.2 47.0 46.6 45.6 4

45.6 47.6 48.6 49.1 49.2 49.0 48.4 46.9 3 45.4 47.7 48.7 49.2 49.3 49.0 48.2 46.5 3

45.6 47.6 48.5 49.0 49.2 48.9 48.3 46.7 2 45.5 47.7 48.8 49.2 49.3 49.0 48.2 46.5 2

44.6 46.0 46.6 46.9 47.1 46.9 46.5 45.3 1 44.6 46.2 46.9 47.1 47.0 46.8 46.4 45.5 1


3D CFD3D CFD GTGT


TM | Battery Pack with Thermal Masses and GT-AutoLion


• Electrochemical integration with GT-AutoLion � validated model

• Build up of the battery cell arrangement and electrical flow

• 4 cells in parallel and 16 cells in series (4p16s)

• Transfer of dissipated heat from battery cell and ave. temperature from thermal mass

Temperature from

thermal masses to

the cells

4 cells in parallel 4 cells in parallelDissipated heat

rate from the

cells to the

thermal masses

02.10.2019

Current profile


Agenda

02.10.2019

Introduction01



02

Results04

Conclusion05



Results | 1C Discharge Battery Pack


Boundary Conditions

• Measurement for 1C Discharge

• Battery cell initial temperature 31-33°C

• Ambient temperature 25°C

• Start-SOC = 0.85

Results

• The gradient of the temperature characteristic is

similar

• Note: model calibration only with 3D CFD!

• Simulation results for the 1C discharge match

the test results very well

• For the case of battery charging, there are

currently deviations between simulation and

measurement

02.10.2019

Different initial

temperature

Test 1C: Max TCell

Test 1C: Min TCell

Sensor

Position


Agenda

02.10.2019

Introduction01



02

Results04

Conclusion05



Conclusion

• GT-AutoLion Cell Calibration successful according to recommended workflow by GT

• Small Error for discharging curves after calibration

• GT suitable for thermal management modeling

• Easy build-up of a battery model with passive cooling

• First verification with battery pack measurements shows good matches

• The model fulfills the defined requirements

• Further investigations are necessary


02.10.2019


Thanks to


02.10.2019

Peter Stopp / Vehicle & Electrification

Dr. Dig Vijay / Thermal Management


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European GT Conference - gtisoft.com€¦ · Agenda 02.10.2019 01 Introduction Cell Calibration...

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