EVS28KINTEX, Korea, May 3-6, 2015

Analysis of the Cooling Performance and

Characteristic Using Lithium-ion Battery for

Eco-friendly Vehicle

Taecheol JeongSsangyong Motor Company, 150-3, Chilgoe-dong, Pyeongtaek-si,

Gyeonggi-do, Korea, taecheol.jeong@smotor.com

Table of Contents

2

1. Motivations

2. xEVs Battery Pack Cooling System Over View

3. Li-Ion Battery Module Discharging Test

4. Li-Ion Battery Pack Temp Profile Test

5. EV Temp Profile Test in Hot Chamber

6. Conclusion and Future Works

Battery Temperature affects vehicle:

- Performance, reliability, safety, life-cycle cost

3

1. Motivations

Temperature affects battery:

- Operation of the electrochemical system

- Round trip efficiency

- Charging acceptance (Regen / Quick Charging)

- Power and energy availability

- Safety and reliability

- Life and life-cycle cost

irreversible chemical reactions

permanent damage of the cell

Desired Operating

Temperature

electrolyte in the cell may

freeze internal resistance

increases

• Battery performance strongly depends on the temperature• Best performance of Li-Ion cells is reached in a very narrow temperature band• So, Battery thermal management system is needed.

Battery power in vehicle is a function of resistance and control limits

Source: ‘VOLTEC Battery System for Electric Vehicle with Extended Range’, 2011 SAE International, 2011-01-1373‘Electric Vehicle Battery Thermal Issues and Thermal Management Techniques’, 2011 SAE International, Alternative Refrigerant and system efficiency Symposium. NREL

4

Li-Ion Battery Resistance Increases with Decreasing TemperatureCapacity Decreases

• Power decreases with decrease in temperature • Impacts power capability of motor and

vehicle acceleration

• Useful energy from the battery decreases withdecrease in temperature

• Impacts driving range and performance of vehicle

Source: ‘Electric Vehicle Battery Thermal Issues and Thermal Management Techniques’, 2011 SAE International, Alternative Refrigerant and system efficiency Symposium. NREL

1. Motivations

2. xEVs Battery Pack Cooling System Over View

• Liquid vs Air Cooling

Liquid-Cooling Air-Cooling Remarks

Images

Advantages&

Disadvantages

Pack temp. uniform - thermally stableGood heat transport capacity Better thermal control Lower volume, Compact designNoise ↓Weight ↑ / Leakage potential Higher maintenanceHigher cost

Separate cooling loop not required Low mass of air and distribution system No leakage concern No electrical short due to fluid concernSimple design Lower cost / Easier maintenance Low heat transport capacity More temperature variation in pack Blower noise

Models of Mass

Production

GM Volt, Spark EV, Ford Focus,Tesla Model S, etc

Mitsubishi i-MiEVHKMC Ray EV, Sonata HEV, Fluence, Priusetc

5

• Oil-cooling case is cooler and reaches steady state much more quickly• Liquid cooling/heating is more effective but, could have more mass, has a potential for leaks,

need more components, and could cost more. Maintenance and repair is more involved and costlier. • Indirect liquid cooling is easier to handle than direct liquid cooling.

Source: ‘Battery Thermal Management in EVs and HEVs:Issues and Solutions’, Advanced Automotive Battery Conference. NREL, Las Vegas, 2001

• Liquid Cooling vs Air Cooling

2. xEVs Battery Pack Cooling System Over View

• Discharge Test

Blower On/ Off & Discharge Test

• Test method

1. 2P6S Module 1ea 1C/1.75C/2.5C rate Discharged

2. 16 Points measuring

3. Non-Active Cooling / Active Air Cooling Measuring Temp change

Module

Dummy

Chamber①

1

Measuring Points

2 3

4

5

6

7

8

9

10

11

12

Airflow

②

13

14

15

16

Measuring Points(Amb Temp)

3. Li-Ion Module Discharging Test

• Discharge Test Results without Blower

40A Discharge: 60 min. 70A Discharge : 35 min.

100A Discharge : 25 min.

Tmax ≤ 34 °C and ΔTmax 5.3°C Tmax ≤ 42 °C and ΔTmax 7.6°C

Tmax ≤ 47 °C and ΔTmax 10.9°C

3. Li-Ion Module Discharge Test

• Result of 70A / 100A Discharge without Blower - Module Temp. 40 °C Increasing

• Case of High Current discharge: Cooling needs

• Discharge Test Results with Blower

40A Discharge: 60 min. 70A Discharge : 35 min.

100A Discharge : 25 min.

Tmax ≤ 31 °C and ΔTmax 4.4°C Tmax ≤ 34 °C and ΔTmax 5.9°C

Tmax ≤ 36 °C and ΔTmax 9.5°C

3. Li-Ion Module Discharge Test

• Result of 70A / 100A Discharge with Blower- Module Temp. max 36 °C : Stable

Discharge-

rate

Non Air Cooled (Blower Off) Air Cooled (Blower On)

∆T Min ∆T Max T Max ∆T Min ∆T Max T Max

1C =40A

60min4.4 5.3 34 1.4 4.4 31

1.75C=70A

35min4.7 7.6 42 1.8 5.9 34

2.5C=100A

25min6.0 10.9 47 5.0 9.5 36

• Active Air Cooled has over 15~20% cooling effect than Non-Air Cooled. • The case of non-air cooled, active cooling may needed when over 2.5C discharge because ofincreasing temperature.

3. Li-Ion Module Discharge Test

• Module cooling Test Results Summary

• Profile for 2.5C Discharge 15min. and 3C Charging 11min.

• 2.5C (100Ah*) discharge on 80% SOC Quick Char’g (11Min.)

• *100Ah: High Speed Driving, discharge consecutively 100Ah

Inlet_2 Inlet_1

Module

Outlet

② Temp. on Inlet_1③ Temp. on Inlet_2

④ Temp. on Outlet

⑤ Temp. outside of pack

① Temp. in chamberQuick Discharge Cycle – Quick Charge Cycle

4. Li-Ion Pack Temp Profile Test

• Temp Profile Test with Air Cooling

2.5 C

3.0 C

discharge

Charge

15 min

11 min

• Chamber Temp 0.2 ℃ ↑• Inlet_1 temp 0.5 ℃ ↑• Inlet_2 temp 0.6 ℃ ↑• Outlet temp 4.0 ℃ ↑• Ambient Temp 3.7 ℃ ↑

4. Li-Ion Pack Temp Profile Test

- TModule,max ≤ 44 °C and ΔTModule,max ≤ 23 °C- TModule,max > 40 °C, Cooling with A/C needed

2.5 C

3.0 C

discharge

Charge

15 min

11 min Module 20_1 Module 20_2

방전시작 21 21

방전 종료/충전시작 30 30

충전종료/방전시작 34 34

방전종료/충전시작 41 40

충전종료 44 43

13

Battery Temp

Vehicle Speed

Motor Torque

Initial Temp: 46 °C

Final Temp: 49 °C

• Ambient Temp: 43 °C• Battery Cooling: Air Blower (With A/Con)• EV Mode Driving 50kph 80kph• Battery Current: Discharge 20~30A (50 kph) 40~50 A (80kph)• Test Result: Amb temp 43 °C, 35 min. EV mode Driving Pack Mean Temp: ∆3 °C ↑

Mean: 20 Nm 28 Nm

Speed: 50 kph

Speed: 80 kph

5. EV Temp Profile Test in Hot Chamber

28 Nm

6. Conclusion & Future works

• Conclusion

1. Battery Pack Thermal management Range definition

- Keep 20~40 °C / case of T max 40 °C, Active cooling and Power Limit Strategy are required.

2. Test result of Module Active air Cooling and non-Air Cooling- non-Air Cooling: Discharge 1C/1.75C/2.5C, ∆T min 4.4 ~ ∆T max 10.9 Increasing, - Air Cooling: Discharge 1C/1.75C/2.5C, ∆T min 1.4 ~ ∆T max 9.5 Increasing Active Air Cooled has over 15~20% cooling effect than Non-Air Cooled.

3. Result for Profile Test of Battery Pack Temp. with Air cooling- Pack Air Inlet, Outlet ∆T=4 ℃ / Each Module surface temperature max ∆T=12 ℃, max T=44 ℃- Battery pack temp increasing, active cooling strategy are required. (Related Battery Life)

4. EV Battery Temp Test in Hot Chamber- Amb temp 43 °C, EV mode Driving 35 min. Pack Mean Temp: ∆3 °C ↑

• Future Works

1. Performance Comparison with Cooling with HVAC and Using Cabin air in vehicle level2. Performance Comparison of Battery Pack Temperature changing with Driving Modes

Thank you

E-mail: Taecheol.jeong@smotor.com