Thermal management of a li-ion battery in a hybrid

passenger car within the development process

Dr. Florence Michel, Daimler AG

19.03.2013

Outline

1. Thermal management of HEV battery

2. Numerical process 3. STAR-CCM+ model validation

4. Thermal behavior of the battery

under real conditions

2 19.03.2013Thermal management of a li.ion battery in a hybrid passenger car, F. Michel, Daimler AG

HEV-battery, S-Class S400 Hybrid

Heat sink

and evaporating plate

Battery Management System

Lithium ion cells

Inlet refrigerant

Current plug

Cell System Control

3 19.03.2013Thermal management of a li.ion battery in a hybrid passenger car, F. Michel, Daimler AG

T(°C)

Temperature in the engine comparment,

Uphill drive 35 km/h

HEV-battery in the S-Class S400 Hybrid

Thermal Management of HEVs, PHEVs and EVs

operating

temperature range

Tmin

Tmax

time period use case

t [s]

T [°C]

4 19.03.2013Thermal management of a li.ion battery in a hybrid passenger car, F. Michel, Daimler AG

((optional))

Overview of the thermal management

development process

H G F E D C B AIKICK OFF

DPT-1 DPT-2 DigEFzg

((optional))

DigBFzg

Validation EFzgValidation

BFzg

review DPT-2

validation serial

capability

review

DigEFzg

review DPT-1

validation vehicle

concept

Start hardware

BFzg

Functional

release

Start hardware

EFzg

data

freeze

DPT-1

data

freeze

DPT-2

data

freeze

DigEFzg

data

freeze

DigBFzg

Start dKA

TAG development process

dKA

5 19.03.2013Thermal management of a li.ion battery in a hybrid passenger car, F. Michel, Daimler AG

Numerical process for thermal management

of a battery

Convection full vehicle

Conduction and radiation

full vehicle Cell data from supplier

CHT computation of battery

STAR-CCM+

Energy management

full vehicle

VehEMent+

(Matlab-Simulink)

Heat source, cool request

Model validation using

measurement results

AC circuit full vehicle

Dymola

Heat transfer refrigerant

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Direct coupling way vs. Tables

T cool_inlet (t)Heat generation =

f(cell temperature, time)STAR-CCM+ VehEMent+

0 500 10000

10

20

30

40

time / s

Plo

ss,b

att /

kW

Driving cycle (e.g. uphill)

Variation battery temperature

Offline

T cell (3D distribution)

Q cell / cool t)

Q cell/ambiance (t)

T cool_inlet (t)

Variation heat losses (t, xi)

STAR-CCM+ VehEMent+

1D/3D coupling STAR-CCM+ -VehEMent+

Tables (indirect coupling way)

Coolant inlet temperature

Benefit: Temp. distribution evaporating plate

Benefit: efficiency, reliability

T cell (3D distribution)

Q cell / cool t)

Q cell/ambiance (t)

7 19.03.2013Thermal management of a li.ion battery in a hybrid passenger car, F. Michel, Daimler AG

• The test-rig includes all moving parts and heat

generating elements of a vehicle

(except AC-system).

• The battery is cooled by coolant. The powertrain

is operated following a city drive cycle with high

electric loads during short-time acceleration and

deceleration phases. The battery SOC is varying

between 40 and 55%.

Test-rig (fragmented)

Measurement in the powertrain test-rig

8 19.03.2013Thermal management of a li.ion battery in a hybrid passenger car, F. Michel, Daimler AG

Boundary conditions for the computation

Flow rate Mean heat losses Inlet temperature

1 L/min 170 Watts 10.5°C

• The drive cycle is computed using VehEMent+ providing the transient heat losses.

• The coolant inlet conditions and heat losses are given as boundary conditions.

I (A) Vel. (km/h)

9 19.03.2013Thermal management of a li.ion battery in a hybrid passenger car, F. Michel, Daimler AG

Numerical model of the HEV battery

container

Jellyroll resin

TIM

R-Jellyroll-container = 0.028 W/m²/K

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Numerical results: temperature distribution

Min Max

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Numerical results, transient computation

Delta T = 3°C

12 19.03.2013Thermal management of a li.ion battery in a hybrid passenger car, F. Michel, Daimler AG

Test conditions:

• Current pulse until constant temperatures

• 370W heat losses

• Coolant: water-glysantin 50-50%

• 10°C inlet temperature, 6l/min

• 30°C ambiance

Measurement in a conditioning cabinet

15mm 15mm

Pos1

Pos2 Pos3 Pos4

20mm 45mm

Thermocouples in the battery

35

1

14

251

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Pos4

Pos3

Pos2

Pos1

Vergleich: T(sim)-T(exp)

-8

-6

-4

-2

0

2

4

6

8

Cell35 Cell28 Cell25 Cell14 Cell01

(°C

)

Pos1_DeltaT

Pos2_DeltaT

Pos3_DeltaT

Pos4_DeltaT

Vergleich: T(sim)/T(exp)

20

25

30

35

40

45

Cell35 Cell28 Cell25 Cell14 Cell01

(°C

)

Pos1_Exp

Pos2_Exp

Pos3_Exp

Pos4_Exp

Pos1_Sim

Pos2_Sim

Pos3_Sim

Pos4_Sim

P4

P1

P2

P3

Numerical results, steady state computation

Comparison num. / exp. results

Temperature difference num. / exp. results

T1

T1+5

T1+10

T1+15

T1+20

T1+25T(°C)

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Pos4

Pos3

Pos2

Pos1

P4

P1

P2

P3

Numerical results, transient computation

15 19.03.2013Thermal management of a li.ion battery in a hybrid passenger car, F. Michel, Daimler AG

Time period for cool down: 5-7min

Cooling is on around 50% of total time

Temperature difference between CAN signal for control and jellyroll between 6 and 8°C

Boundary conditions:

• 300W heat losses constant

• 10°C cooling plate temperature

if cooling on

Jellyroll max. temperature

Jellyroll min. temperature

CAN signal temperature

Cooling plate temperature

Thermal behavior with temperature control

Temperature control:

- T > 32°C cooling on

- T < 28°C cooling off

0 10 20 30 40 50 60

T (°C)

Time (min)

Thermal behavior (Jellyroll, cooling plate)

T1

T1+5

T1+10

T1+15

T1+20

T1+25

T1+30

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30

31

32

33

34

35

36

37

38

0 10 20 30 40 50 60

(°C

)

Time (min)

Maximum jellyroll temperature for ambient temperatures of 35°C or 90°C

Ambience

35°CAmbience

90°C

Temperature difference between T.amb = 35°C and T.amb = 90°C (after one hour):

∆T, jellyroll = 31,8 -30,8 = 1°C

Effect of the ambient temperature

Boundary conditions:

• 200W heat losses constant

• 10°C cooling plate temperature

• Ambience: 35°C or 90°C with a heat transfer coefficient of 120W/m².K

17 19.03.2013Thermal management of a li.ion battery in a hybrid passenger car, F. Michel, Daimler AG

Temperature distribution in the battery (z- and x-sections):

Negligeable effect of conduction through internal

screws

10 90 10 90

Effect of the ambient temperature

18 19.03.2013Thermal management of a li.ion battery in a hybrid passenger car, F. Michel, Daimler AG

Conclusions

� Numerical methods have been developed in order to predict the transient temperature

distribution of a refrigerant cooled battery.

� These methods can be applied to batteries cooled by water or air in HEVs, PHEVs and

EVs.

� A conjugate heat transfer model has been created in STAR-CCM+. The comparison

with experimental results shows a good agreement within 4K for the temperature of

the cell can.

� The battery temperature is computed in transient under vehicle electrical and thermal

loads. The effect of the vehicle ambient conditions on the battery cells' temperature is

negligeable (less than 1K).

19 19.03.2013Thermal management of a li.ion battery in a hybrid passenger car, F. Michel, Daimler AG

Thank you for your attention !!!

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