Battery Pack Design - Värmeöverföring · based on suitable models ... Avo R MVKF25-vt17 Battery Pack Design 12 Lithium Battery Technologies ... • Simple approach @ limited data

Battery Pack DesignMVKF25-vt17

Mechanical and electrical layout, Thermal modeling, Battery management

25-27/4

Avo Reinap, IEA/LU

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Avo R MVKF25-vt17 Battery Pack Design 2

Goals• Design and dimensioning of battery pack

based on suitable models– evaluate suitable battery technologies, specify cell

and packing, electric and thermal termination– battery development and energy management

systems, predict state of charge, health, function, ..– test battery compatibility to operating conditions,

current waveforms

Ageing model Thermal model

Electrical model

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Background A

• Vehicular application– Electrification improves energy

usage – hybrids• use ICE at 35% instead of 10-

20% efficiency• Reuse deceleration energy for

acceleration– Pure renewable fuel/energy

• System view– Charging, static vs dynamic– Compatability, AC current loading

Avo R 3

Battery and Propulsion

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Background B

• Part-III Battery usage– Pack design (Ch5) – Management (Ch6)– State and degradation (Ch7)

• Part-I & II Li-ion battery technology– Cell components (Ch1)– Cell materials (Ch3)– Cell design (Ch4)

Avo R 4

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Avo R MVKF25-vt17 Battery Pack Design 5Avo R 5

Background C

• Electrical machine design• Directly air-cooled cooled

laminated machine windings• Indirect oil-cooled stator-core

and end-turns• Enhanced winding thermal

conductivity

Fig.Ref.: EDPC’14, EDPC’15

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Content

• Design– path from topology

sketching to practical realization

• Cell, Module, Pack/Bank• Battery = Energy storage

[Wh] & Power supply [W]– Applications: Vehicle/Grid– Technologies: Li-ion

• Battery cell– Geometries and dimensions– Characteristics and

properties

• Cell “virtual” packing• Electro-Thermal models• Packing examples• Thermal design

– Cells, modules, backs• Battery Management System

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Design

• A cross-road of different disciplines• Multi-dimensional (analysis) & multi-objective (synthesis)• ..

Construction Production

Energy Conversion

kg kW, kWh

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Specific energy and power

• Specific energy originates from material chemistry

– Capacity capability

• Specific power is related to material physics and production

– Internal power losses and thermal constrains – durability and safety

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Value chain for EV batteries

• From cell realization to recycling (excluding raw materials)• Vehicle power (performance), energy (range) and integration (BMS)

Fig.Ref.: B. Averill, P. Eldredge, “General Chemistry: Principles, Patterns and Applications”

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Lithium-ion batteries:How do they work?

https://www.youtube.com/watch?v=2PjyJhe7Q1g

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Electrochemical cell

• Chemical reaction = two half-reactions: oxidation+reduction=redox– Side reactions due to thermal loads, pressure?

• Active, electrodes, non-active, the rest including electrolyte, components

B. Averill, P. Eldredge, “General Chemistry: Principles, Patterns and Applications”

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Lithium Battery Technologies

• Optimal performance and lifetime capacity

• Case sensitive: application vs cell configuration

Abbr Wh/kgLithium cobalt oxide LiCoO2 LCOLithium manganese oxide LiMn204 LMO 4.0V 114-159 Lithium iron phosphate LiFePO4 LFP 3.2V 114-138Lithium nickel manganese cobalt oxide LiNiMnCo02 NMC 3.7V 93-171Lithium nickel manganese aluminum oxide LiNiCoAlO2 NCALithium titanate Li4Ti5O12 LTO

R. Purkayastha, R.M. McMeeking, "A Linearized Model for Lithium Ion Batteries and Maps for their Performance and Failure" ASME

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Cell material properties example

material Thickness [μm]

Thermal conductivity

[W/mK]

Electrical conductivity

[S/m]+ I collector aluminum 20 238 37.8e6+ Electrode 106 1.58 (wet) 13.9 (wet)Electrolyte wetSeparator 25 0.34 (wet)- Electrode 111 1.04 (wet) 100 (wet)- I collector copper 14 398 59.6e6

case 162 0.16

M. Yazdanpour, “A circuit-based approach for electro-thermal modeling of Lithium-Ion batteries”

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Thermal management system• Historic usage affects availability of

energy and power in future– BMS = preferred and “optimized”

usage– BTMS includes temperature control

• Purpose of BTMS– Maintain operational temperature– Assure temperature uniformity

• Challenges– Temperature increase at high power

load– Heat-up time in prior to start-up

Avo R 14

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Battery performance degradation

• Degradation – deterioration of useful capacity and power capabilities

• Identification of physical and chemical processes behind degradation mechanisms . Origins related to technology and usage.

• SoH – state of health remaining capacity due to ageing

http://epg.eng.ox.ac.uk/content/degradation-lithium-ion-batteries

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Battery failure

• Safety=thermal stability– BTMS is very important for

performance and safety

• Failure mechanisms– External/internal – internal short

circuits– Mechanical, electrical, thermal

– abusive conditions

• Failure propagation from cell to module and pack

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Thermal runaway

• Rapid temperature increase– Most likely due to internal

spontaneous short circuits due to impurities (that can grow during time as side effect of chemical reactions)

• Avoid thermal runaway– Overcharge/discharge protection

activated by over pressure– Current interrupt device (CID)– Positive temperature coefficient

(PTC) – Separator specified for PTC & CID,

layered separators for reducing internal short circuits

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Question 1.1

Avo R 18

• What are the criteria for the design of suitable thermal management system for a battery back?– Battery (cell) design? – Parameters related to heating?– Factors influencing the heat transport and

dissipation?

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Battery modelling A

Avo R 19

• Simple approach @ limited data• Cell voltage U=Eo-RoI where Ro is internal resistance

and Eo is open circuit voltage (OCV) – Ignoring that Eo and Ro depends on SoC and temperature

• Heating power Q=(RoI)2 only Ohmic losses– Ignoring reversible heat loss, Ro depends on SoC and

temperature

• Transient temperature rise T=QRh(1-e-t/RhCh)– Thermal properties are not an easy target!

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Equivalent circuit relations

Relation Electrical circuit

Magnetic circuit

Thermal circuit

Cooling circuit

Potential U=E·l N·I=H·l =G·l P=·l

Flow I=J·A Φ=B·A Q=q·A Q=v·A

Conductive element

G=γ·A/l

G=μ·A/l G=λ·A/l G=·A/l

Ohm’s Law U=I·R N·I=Φ·R =Q·R P=Q·R

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Battery modelling B

• Depth of discharge DoD 0 1 max(Ucell) min(Ucell)

• Inner voltage source (OCV) E(DoD)=Ucell(I,DoD)Rdch(DoD)*I

• Charge Rch and discharge Rdchresistors depends only on DoD

– Usually Eo and Ro available– Also ∆U and ∆T

Avo R 21

Ageing model

Electrical model

current Thermal model

power

temperaturevoltage

DoD SoH

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Cell construction• Electrode arrangement: spiral

wound jelly roll, stacked electrodes, bobbin type

• Geometry: Cylindrical, Prismatic, Pouch, Button

• Components– Case: plastic (PET) or metallic

(steel, Al)– Core=active components

+collectors, separator– Terminals

www.toray-eng.com

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18650 Li-ion

• Standard (size) cylindrical Li-ion cells ø18h65mm

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Prismatic Cells

• Some cell producers– Hitachi, Samsung-SDI,

Panasonic (Sanyo)

Prismatic cell L, [mm] W, [mm] T, [mm] M, [kg] U, [V] C,[Ah] p, [W/kg] c, [Wh/kg]

Hitatchi-1 148 91 26.5 0.72 3.6 28 2300 140SDI-1 37SDI-2 60SDI-3 94

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Kokam’s SLPB cell

• SLPB – Superior Lithium Polymer Battery

• Pouch type improved heat dissipation due to larger surfaces

• Example 240Ah 4.8kg cell– Pheat=1.1kW @ 480A– Acool=2x0.15 m2

– V=46.2x32.7x1.58 cm

Kokam.com

0 500 1000 1500 2000 250060

80

100

120

140

160

180

200

220

240

260

SLPB160460330

specific power, pcell [W/kg]

spec

ific

ener

gy, w

cell [W

h/kg

]

Kokam large cells

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Overview of cell producers for xEVs

• It is easier to find producer than product ;)

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Battery back sizing

• Number of series connected cells in strings– Ns=Udc/Ucell

• Number of parallel connected strings– Np=Energy/(Ns*[Wh/kg]*[kg])– Np=Energy/(Ucell*”cell capacity”)

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Calculation example

• Ch4 – Cell data• Ch5 – EV and HEV spec

– 300 V * 100 A– Pmax = 2*30kW– P/E ratio 2 and 20

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Specification list

LinkSource Sink

• Forced heating/cooling for battery back– Concepts, topologies, realization ideas, …

• Battery cell – Construction, properties, heat sources, thermal loads, …

• Heat conductor– Thermal accessibility, thermal contacts, …

• Cooling plate– Realisation, performance, …

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Question 1.2

Avo R BTMS 30

• Battery pack specification– Power demand?– Capacity?– Weight or size?

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Thermal design

• Methods, models, calculation examples for thermal design• Practical realisation examples from some car manufacturers

Heat

Electricity

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Thermal modelling

LinkSource Sink

• Models 1D, 2D, 3D analytic or numeric– Computation time vs accuracy, …

• Single cell, a module of cells, battery back – Specification of equivalent cell volume with specific losses, …

• Assembling, heat transport and temperature distribution– Mechanical assembly and thermal accessibility, thermal contacts

• Integration of active cooling circuits– Realisation, estimation of coolant flow and performance, …

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Thermal integration

• Direct cooling where it is most needed in order to minimize heat transport through the solids that causes interior temperature rise and uneven temperature distribution

• Consider the effects of thermal cycling and expansion

• Experiences from other electric drive components

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Thermal design simplifies control and BMS

• Cells (EL+Chemi) – modules (Heat) – battery pack (Duty)

• Battery thermal management – Keep temperature & use

little energy for operation– Keep it Simple is the rule of

the day • Prototype development and

prototyping supported buy models– CAD (SW) – components

and parts (Ansys or Comsol – fluids and solids) – system (Simulink/Matlab)

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cell Rcell surf

Ccell P

fluidRlink

Thermal model

• representing physical reality (?)• Main focus on only on reasonable

cell surface temperature surf as cell is remains unknown (?)

– surf = fluid + R*P• Thermal resistances: simplifications

vs idealisation• Practical realization for fluid

dynamics• Thermography for rapid thermal

assessment influidoutfluid

h

cellcell

cellsurf

cellcell

cPQ

CRCP

dtd

,,

1

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Model library

• Impedance based equivalent circuit models, dynamic experiment based

• Physics and chemistry-based models relay on model parameterisation and properties

• Energy or power-flow models are typically used on a system level

• Empirical models black box models suitable for control not design

Avo R 36

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Cell library

• Selected cell examples: cylindrical, prismatic, pouch

• This information is used for virtual packing and rough estimation on temperature rise and distribution

Manufacturer configuration Geometry Voltage Capacity Specific power Weight

[mm] [V] [Ah] [W/kg] [g]Panasonic Cylindrical Ø18.5x65.3 3.6 3.2 120 48.5

Hitatchi Prismatic 148x91x26.5 3.6 28 2300 720Kokam Pouch 462x327x15.8 3.6 240 360 4780

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Cell “virtual” packing

• For 300V there is need of 84series connected 3.6V cells

• First draft of 148x26.5 mm prismatic cell arrangement where 5 mm distance is left between the rows and groups of 7 cells

• First draft of ø18 mm 4 parallel cylindrical cell arrangement with cooling channel in between the cells

• Not only visualization but a parameterized model with coupling to finite element analysis (FEA)

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Electric connection of cells

• Series-parallel connections• Connection-bars and cables

are part of heat generation but also distribution

• Nickel plate + spot welding = healthy low resistance connections

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Estimation of thermal conductivity

• Equivalent thermal conductivity of a coil is given by the filling factor of the conductor foil (copper in this example) and the thermal conductivity of the medium between the conductor foils

• jelly-roll:12% Al+Cu λ>200W/mK, 6% eparator λ<0.35W/mK, rest λ~1W/mK

• Across coil or roll λ~1W/mK, along λ>>1W/mK

inscond

fcondfins

ins

f

cond

f

eff

kkLkLkLL

11

fcondfins

inscondeff kk

1

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Using 2D FE for sketching• FEMM electromagnetism,

heat transfer, electric currents

• Easy to use, library of Matlabfunctions– Drawing the endpoints of the lines

and arc segments for a region,– Connecting the endpoints with

either line segments or arcsegments to complete the region,

– Defining material properties and mesh sizing for each region,

– Specifying boundary conditionson the outer edges of the geometry.

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Battery pack with cylindrical cells• “Empty” space between cells• Cross-flow through battery

module– Narrow spacing – expectedly no

cooling– Large spacing for sake of better

cooling is often considered impractical

• CFD vs “fast” design approaches

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Battery back with prismatic cells

• Temperature homogenization analysis• Analysis of thermal runaway

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Battery pack with pouch cells

• Coupled electro-thermal FE+model order reduction (MOR) simulation compared to thermographic images

– A reduced order model (ROM) based on singular value decomposition (SVD)

• Direct air-cooled Li-ion pouch battery cell in order to improve the understanding (modelling) and practical realization of battery module

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Vehicular application

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Chevy 104kW 20kWh

• GM Volt and Spark EV use thin prismatic shaped cooling plates in between the cells with the liquid coolant circulating thru the plate.

• The Volt cooling scheme is very effective from a cooling point of view but it is complicated. The cells are encased in multiple plastic frames

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Tesla S 285kW 70kWh

• Tesla snakes a flattened cooling tube thru their cylindrical cells resulting in a very simple cooling scheme with very few points for leakage.

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BWM i3 125kW 21-33kWh

• The BMW i3 cools the bottom of the battery case with refrigerant eliminating the liquid coolant entirely.

• New energy dense lithium ion cells (50% more)

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Integration example by BMW

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Integration example by Tesla

• 60kWh, 352V, 14 modules, 6216 cells in groups of 74=6x14• 85kWh, 402V, 16 modules, 7104 cells

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Integration example by Tesla

Avo R 53

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Accommodation of cylindrical cells

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• Single stage heat transfer insufficient hA vs UA

Cool-plate and coolant

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Avo R MVKF25-vt17 Battery Pack Design 56Avo R BTMS 56

CoolantAir H2 C02 H20 Tr Oil

, degC 20 120 20 120 20 120 20 120 20 120c, kJ/kgK 1.00 1.01 14.2 14.5 0.85 0.94 4.19 4.25 1.71 2.11, kg/m3 1.20 0.89 0.08 0.06 1.83 1.36 999 946 879 816λ,mW/mK 26 33 178 227 16 24 594 686 111 102, uPas 18 23 8 11 14 19 1000 200

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Conjugate heat transfer• The character of flow is

described by Reinolds number,

• the heat transfer is expressed by Nusselt number

• and the coolant is described by Prandtl number

• The hydraulic diameter is related to the geometric layout of the cooling channel

hin

h DAQvD

1Re

bulkwall

hh k

qDDkhNu

kcpPr

perimeterareaDh

4

dcool

dcond

L Lh

out in

win

cQPcool

cool

heat

hAP

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Heat transfer mapping

• Driving parameters for cooling P=f(out,Q) at in

• Flow (Re) and coolant (Pr) characterization

• Heat transfer – correlations (Nu) and – coefficient h

• Wall and winding temperature• Pressure across cooling channel

– Power for supply• Expected cooling power

P=f(w,Q) at in

0 100 200 300 400 500 600 700 800 900 100020

40

60

80

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120

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100100

100100 100

300

300

300300

500

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900

900

1100

1100

1100

1300

1300

1300

1500

1500

flow rate, Q [L/min]

outle

t tem

pera

ture

, ou

t [ C

]

Cooling power, p=cpQ(out-in) [W]

0 100 200 300 400 500 600 700 800 900 100020

40

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outle

t tem

pera

ture

, ou

t [ C

]

Reynolds number, Re=2dhQ/(A) [-]

0 100 200 300 400 500 600 700 800 900 100020

40

60

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100

120

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200

220

6.6

6.6

6.6

6.8

6.8

6.8

7

7

77.

2

7.2

7.2

7.4

7.4

7.4

7.6

7.6

7.6

7.8

7.8

7.8

8

8

8

8.2

8.2

8.48.6


outle

t tem

pera

ture

, ou

t [ C

]

Nusselts number, Nu=f(Re,Pr) [-]

0 100 200 300 400 500 600 700 800 900 100020

40

60

80

100

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340

360

360

360

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380

380

380

400

400

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420

420

440


outle

t tem

pera

ture

, ou

t [ C

]

Heat transfer coefficient, h=Nu k/Dh [W/(m2K)]

0 100 200 300 400 500 600 700 800 900 100020

40

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220

20

20

2020

40

40

40

40

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60

60

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80

80

100

100

120

120

140

160flow rate, Q [L/min]

outle

t tem

pera

ture

, ou

t [ C

]

Temperature across boundary, Pcool/(hAcool) [C]

0 100 200 300 400 500 600 700 800 900 100020

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20002000

40004000

60006000

8000

8000

800010000

10000

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1200014000


outle

t tem

pera

ture

, ou

t [ C

]

Pressure drop, dP [Pa]

0 100 200 300 400 500 600 700 800 900 100020

40

60

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5050

50

100100

100

150150

150

200200


outle

t tem

pera

ture

, ou

t [ C

]

Ideal cooling supply power, dPQ [-]

0 100 200 300 400 500 600 700 800 900 10000

50

100

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250

100

100100 100

300

300

300300

500

500

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1300

1300

1500


wal

l tem

pera

ture

, ou

t [ C

]

Cooling power, p=cpQ(out-in) [W]

0 5 10 15 20 25 30 35 40 45 5020

21

22

23

24

25

26

27

28

29

30


outle

t tem

pera

ture

, ou

t [ C

]

cooling power, p=cpQ(out-in) [W]

10001000

1000

10001000

4000

4000

4000

4000

7000

7000

7000

10000

10000

10000

13000

13000

c=3500J/kgK, =900kg/m3

B. Sundén, “Introduction to Heat transfer”

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Thermal analysis of cell assembly

• Geometric data– Defined by German standard

DIN 91252

• Heat transfer inside the cell– From cell to module and

pack– Cell = Jelly-roll (heater) +

carrier (assembly)

• Heating power – Worst case P=I2Ro=50W

Hitachi 3.6v 35Ah 0.8mΩ@10A155x27x118 incl terminals 810g

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Thermal accessibility of a cell

• Available thermal connection areas– Large long sides 2x134cm2

but low thermal conductivity– Sides, lateral sides 2x24cm2

and Bottom side 39cm2

• Bottom and short sides have expectedly better inherit thermal contact

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Inside a battery cell

• Cell dimensions are known, jelly-roll geometry only guessed• Heat conductivity defined in-plane and cross-plane for whole cell

unit and jelly roll (including heat capacity)• Important part for thermal models are termination and equivalent

jelly-roll

DIN SPEC 91252:2011Lundgren et al 2016

H. Lundgren et al, ”Thermal Management of Large-Format Prismatic Lithium-Ion Battery in PHEV Application”

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Surface temperature response

• Thermal vs electric power extraction and comparison

• Thermal conductivity– Through-foil

0.95W/mK– Along foil 30.8 W/mK

H. Lundgren et al, ”Thermal Management of Large-Format Prismatic Lithium-Ion Battery in PHEV Application”

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2D FE over cross-sections

Case Qbase[W]

Qlateral[W]

max[oC]

1 50 0 60

2 33 17 55

3 21 29 44λcell=1 W/mK

λcell=20 W/mK

Qv=140W/dm3, surf=30oC

6054484236

Temperature , [C]

30

2

1

3

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Observations A

• Battery cell– P=50 W heating, 1/R=0.6 0.5 0.28 K/W, ∆=30 25 14 K

• Heat conductor– Ideal 1/R=0 K/W, ∆=0 K

• Cooling plate– Ideal fluid=wall=surf=30oC

LinkSource Sink

50 W per cell

surf=30oC wall=30oC fluid=30oCcell= surf+Δ

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Realization A

• Mechanical assembly in “cross” plane direction

• Thermal enhancement both in plane directions– Lateral clamp or forcing plate– Battery to base contact

• ..

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Cell clamped into heat conductor

Case Qbase[W]

Qlateral[W]

max[oC]

1 34 16 51

2 32 18 54

3 27 23 72

Qv=140W/dm3, surf=30oC

6054484236

Temperature , [C]

30

-0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

length, [m]

heig

ht, [

m]

10μm gap ∆gap=3oC100μm gap ∆gap=21oC

3

2

1

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Cell linked to cool-plate

Case Qbase[W]

Qlateral[W]

max[oC]

1-30 36 14 53

2-h1 35 15 68

3-h2 35 15 148

Qv=140W/dm3, fluid=25oC

6054484236

Temperature , [C]

30

h1=1000W/Km2 wall ∆wall=15oCh2=200W/Km2 wall ∆wall=95oC

-0.1 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.1

-0.02

0

0.02

0.04

0.06

0.08

length, [m]

heig

ht, [

m]

32

1

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Transient heating

• 5 minutes between the frames (FEMM transient HT)• Hot side of the scale (usually presented in between 20-30oC)• One dominating heat capacitance only

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Summary

• Battery cell– ∆b=30 25 14 K @ 50W – actual load is lower

• Heat conductor– Insufficient thermal contact 0.1 mm air ∆c=20K @ 50W

• Cooling plate– Insufficient heat transfer h2=200W/Km2 wall ∆wl=95oC

LinkSource Sink

50 W per cell

surf= wall+Δc wall= fluid+Δw fluid=30oCcell= surf+Δb

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Evaluation of direct forced cooling

• Cooling channel arrangements

• Thermography of heat transients

– 300 A DC– 400-500 L/min

• Location of hot-spots – “turns” of the layer

edges where the cross section is less than 10 mm2

– Edge layer 1 is closest to air-gap

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Thermal control and management

• ..by thermal design and active cooling• J. Li, Z. Zhu, “Battery Thermal

Management Systems of Electric Vehicles”, MSc Chalmers 2014

• 29.5/17.7 kWh• 1700/270 kg

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Energy ManagementBattery management system

• Monitoring – measure what is important• Control – keep it optimal and constrained• Diagnosis – keep battery cells healthy

Information

Energy

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Battery Management System - BMS

• Best and safe use of energy• Voltage U+∆U and temperature

+∆ management: cell balancing or equalizer, check margins

• Charge/discharge– Integration of current – SoC– Power and capacity fade – SoH

Avo R 73

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Charge and discharge control

• maintain the voltage limits while respecting the current and temperature limits

• LOW Constant current charging followed by voltage and temperature control

• HIGH current for constant voltage charging• Combined CV+CC

Avo R 74

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Cell balancing

• Voltage equalization, which is to fill up energy and maximize capacity and life by ”removing” unbalanced weak links

• Active/passive –taking/wasting energy

Avo R 75

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BMS development

• Overall functional safety is better match to global FPGA than to local micro processor units– parallelism for performance with fail-safe logic

Avo R 76

https://www.altera.com/solutions/industry/automotive/applications/electric-vehicles/battery-management-system.html

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BMS function structure

• I/O, monitoring, decisions and safety relevant funtionsAvo R 77

http://www.avl-functions.de/Battery-Management-S.30.0.html?&L=1Ageing model

Thermal model Electrical model

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BMS control sequence

• Intelligent batteries due to base functions of a battery management system

Avo R 78

http://mocha-java.uccs.edu/ideate/courses.html

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BMS basic functions

• Cell protection, charge control, demand management, SoC and SoH determination, cell balancing, authentication and identification, communication – are some objectives for BMS

Avo R 79

http://www.mdpi.com/1996-1073/4/11/1840/htm

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BMS Scope and Failure Consequences

Avo R BTMS 80

http://www.mpoweruk.com/bms.htm

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BMS architectures for xEVs

• Communication, reliability and accuracy• Practical attachment, number of components and connections• Few architectures with different features in connections and

communication

Avo R 81

http://www.electronicproducts.com/Power_Products/Batteries_and_Fuel_Cells/Battery_management_architectures_for_HEVs.aspx

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Practical implementation

• Added intelligence, where and how? Sharing information, history and communication

Avo R 82

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Multicell Battery Stack Monitor

• Component name LTC6802-1, Up to 12 cells, 13 ms measurement interval, up to 1000V, passive cell balancing

Avo R 83

http://www.linear.com/product/LTC6802-1

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BMS sensor module

MM9Z1 638 4-Cell Lithium Battery BMS unit•battery stack monitor IC can measure a number of cell voltages and provide for the discharge of individual cells to bring them into balance with the rest of the stack

Avo R 84

http://www.nxp.com/products/automotive-products/energy-power-management/can-transceivers/reference-design-mm9z1-638-4-cell-

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Some future trends by Bosch

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Back to Battery modelling

• power_battery, power_pattery_temperature• State of the art model for concept development and

evaluation

Avo R 86

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Physics coupled equivalent circuits

• Battery equivalent circuit models– Rint model Eo, Ro– First order (adds) R1, C1– Second order (adds) R2, C2

• Impedance model– Electrochemical impedance

spectroscopy (EIS)– Coupled to pfysics (?)

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Testing batteries

• Electrochemical dynamic response

– Respons is related to ion-current/diffusion rate in the cell

– Slower response for weaker batteries

• Characterization– LF dubbed diffusion– MF charge transfer– HF migration

• Batteries with faded capacity suffer from low charge transfer and slow active Li-ion diffusion.

http://batteryuniversity.com/learn/article/testing_lithium_based_batteries

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Useful links and Aknowledgement

• mpoweruk.com• Batteryuniversity.com• liionbms.com/php/cells.php

• Aknowledged authors and their results shown on the previous pages (with some links and references)

Documents

Battery Pack Design - Värmeöverföring · based on suitable models ... Avo R MVKF25-vt17 Battery Pack Design 12 Lithium Battery Technologies ... • Simple approach @ limited data