1. Japan research of thermal propagation test
EVS-GTR IWG#15

2. Reminder of Japan research in phase2
To consider conditions of world round robin test, Japan conducted repeatability and reproducibility confirmation test in advance.
Different organizations inside Japan conducted thermal propagation test according to current draft, using same sample and same initiation method (Nail).
Thermal propagation test draft
Institutes A B
Sample X ←
Initiation method
Nail
Number 1 3
Institute A
Institute B
Confirm reproducibility
Confirm repeatability

3. Reminder of Japan research in phase2
It is possible to confirm which parameter has repeatability and reproducibility.
Based on these results, we would like to discuss conditions and criteria of world round robin test.
Sample 1 2 3 4
Institute A B
Thermal runaway of initiation cell occurs/ not occurs
Thermal propagation occurs/ not occurs
Fire and explosion occurs/ not occurs
Voltage drop
Temperature rise
Pressure of pack :

4. Conditions Condition Reason Nail Material Alloy tool steel Steel
Reference
(Phase1 Part1)
Nail
Material
Alloy tool steel
Steel
Same as Phase1 Part1 condition.
Diameter
3mm
More than 3mm
Within Phase1 Part1 condition.
Angle
60° ° ↑
Speed
0.1mm/sec
mm/sec
depth
½ of cell height -
Because of test equipment spec
SOC
100%
90/95% or more
Temperature
Depends on test place
25±2°C
Institute B doesn’t have air conditioner in test booth.
Position of target cell
See page 5
Surrounded by other cells. Thermal propagation is likely to happen.
Insertion point of cell
See page 6
To surely cause internal short circuit.
Modification of pack
See page 7
Made holes for nail.
Voltage and thermocouple points
Target cell, surrounding cells and various points inside pack
To detect thermal runaway of trigger cell and surrounding cells.
Pressure sensor point
Lower case near front

5. Conditions Position of target cell
Cell 5 is surrounded by other cells. Thermal propagation is likely to happen.
Module1 2 3 4 8 7 6 5 10 11
Cell 1 9 12
Module2
Target cell
（Cell5 in Module2）

6. (5.5mm away from center of vent)
Conditions
Insertion point of cell
Inserted nail from cell safety vent.
There are 4 electrodes inside cell. To surely cause internal short circuit, we selected below point.
Nail
Module2
Cell 1
5.5mm 4 5 8 9 12
5.5mm A A
Cell vent 2 3 6 7 10 11
Insertion point
(5.5mm away from center of vent)
Electrode
Section A-A

7. Conditions Modification of pack for nail
Made holes (Φ5mm) in plastic cover and upper case.
Nail(Φ3mm)
Hole for nail
Φ5mm
Upper case
Plastic cover
Cell

8. Variations were observed.
Results
Sample 1 2 3 4
Repeatability/
Reproducibility
Institute A B
Thermal runaway occurs/ not occurs
Occurred ←
High
Thermal propagation occurs/ not occurs
Not occurred
Fire and explosion occurs/ not occurs
Voltage drop of initiation cell P9
Variations were observed.
Temperature of Initiation cell and adjacent cell
P9, 10, 11
Pressure of pack
P12
Sample1
Sample2

9. Results (Initiation cell)
Voltage: There were variations of voltage drop in each sample.
Temperature:
In short term, there were variations in each sample.
In long term, the temperature of all cells settled at similar value.
Voltage
Temperature 2 3 6 7 10 11
Cell 1 4 5 8 9 12
Module2
Initiation cell
－: Sample 1 (Institute A)
－: Sample 2 (Institute B)
－: Sample 3 (Institute B)
－: Sample 4 (Institute B)
Voltage drop

10. Results (Adjacent cell)
Voltage: No voltage drop.
Temperature:
In short term, the temperature of sample1 was higher than other samples.
In long term, the temperature of all cells settled at similar value.
Voltage 2 3 6 7 10 11
Cell 1 4 5 8 9 12
Module2
Initiation cell
－: Sample 1 (Institute A)
－: Sample 2 (Institute B)
－: Sample 3 (Institute B)
－: Sample 4 (Institute B)
Temperature
Voltage drop of initiation cell

11. Results (Adjacent cell)
Voltage: No voltage drop.
Temperature:
In short term, the temperature of sample1 was lower than other samples.
In long term, the temperature of all cells settled at similar value.
Voltage 2 3 6 7 10 11
Cell 1 4 5 8 9 12
Module2
Initiation cell
－: Sample 1 (Institute A)
－: Sample 2 (Institute B)
－: Sample 3 (Institute B)
－: Sample 4 (Institute B)
Temperature
Voltage drop of initiation cell

12. Results (Pressure of pack)
All samples were similar curve though the pressure of sample 4 was lower than the other.
－: Sample 1 (Institute A)
－: Sample 2 (Institute B)
－: Sample 3 (Institute B)
－: Sample 4 (Institute B)
Voltage drop of initiation cell

13. Difference of short term temperature
After the test, melting places of plastic cover were different.
Sample 1 (Institute A)
Sample 2 (Institute B)
Melting
Module2
Module2
Insertion point
Hole
Initiation cell
Sample 3 (Institute B)
Sample 4 (Institute B)
Module2
Module2

14. Difference of short term temperature
The way how to vent were different.
Only the vent of sample1 was opened partially.
Sample 1 (Institute A)
Sample 2 (Institute B)
Gas vent
Partially opened
Sample 3 (Institute B)
Sample 4 (Institute B)
Full opened

15. Difference of short term temperature
Direction of gas released immediately after thermal runaway may have been different due to the difference of how to open vent. ⇒Only in sample 1, the temperature of cell 4 was higher.
Sample1
Sample 2, 3, 4
Temp sensor of cell 4
Cell 1
Cell 4
Cell 5
Cell 8
Cell 9
Cell 12
Cell 1
Cell 4
Cell 5
Cell 8
Cell 9
Cell 12
Cell 1 4 5 8
Cell 1
Cell 4
Cell 5
Cell 8
Gas direction
Gas direction

16. Difference of short term temperature
We are estimating 2 reasons why how to vent was different. ⇒We are going to conduct additional test to clarify the reason.
Estimating factor
Note 1
Variation of cell
Variation of opening vent 2
Variation of test condition
Positional displacement of nail (As shown below)
5.5mm
5.5mm

17. Additional confirmation test
Condition
(Reference)
Test reported above
Test1
Test2 -
To confirm repeatability of venting
To confirm influence of nail position
Cell/Module/Pack
Pack
Cell/Module ←
Nail
Material
Alloy tool steel
Diameter
3mm
Angle
60°
Speed
0.1mm/sec
depth
½ of cell height
SOC
100%
Nail insertion point
5.5mm
4.5 / 6.5 mm
(TBD)

18. Conclusions
Conducted thermal propagation test at institute A and B to confirm repeatability and reproducibility of thermal propagation test.
All samples were no propagation, no fire and no explosion. But voltage drop, pressure and temperature rise in short term were different in each sample.
The variation of temperature rise was due to the difference of how to vent. We will conduct additional test to clarify why venting of each cell was different.
Based on these results, we would like to discuss and decide how much degree of variation is accepted.

19. Future Plan 2017 2018 2019 2020 IWG Japan Research Round robin test
#14
#15
Report
Report
Repeatability and reproducibility test (Ｎａｉｌ)
Additional test (Ｎａｉｌ)
Repeatability and reproducibility test (Heater)
Discussion
Decision method how to conduct round robin test
Round robin Test

20. Appendix

21. Q(JRC)&A No Page Question Answer 1 6
What was the status of the safety functions/devices of the pack (e.g. cooling system, BMS) after removing vehicle?
Not removing, but not working 2 9
How does the CID influence nail test?
When thermal runaway happens, pressure inside cell increase due to gas. Consequently CID works. 3 10
A temperature above 200C was reached for adjacent cell in sample 1. Did this cell exhibit a thermal runaway?
Why does the adjacent cell in sample 1 start at a higher temperature than in the other samples?
No, thermal runaway of adjacent cells didn’t occur. It was just thermal diffusion from initiation cell.
Because in sample 1, the gas was ejected to adjacent cell, the temperature censor of adjacent cell detected gas temperature. 4 12
How does the hole (generated by nail penetration) influence the pressure measurement?
We haven’t checked yet.

22. Q(OICA)&A No Page Question Answer 1 2
Clarification needed regarding test sample: 4 tests done on the same test object or 4 identical test objects?
4 same kind test objects.
They were removed from vehicles registered in same year. -
Have you considered the influence of battery pack design and cell/module configuration and positioning of the pack on the vehicle for the thermal propagation performance? For the ability to contain a thermal event and reduce risk of occupant exposure?
Yes.
This pack was under the floor and has gas release mechanism (vehicle doesn’t have this). So we conducted this test with only pack. Not to lose function of this pack for thermal event, we minimized pack modification.

23. Q(OICA)&A No Page Question Answer 3 4
Were the whole range of test conditions, e.g. nail diameters >0.3mm, speed of nail mm/s, nail angle degrees, depth of insertion... Investigated/considered by the test labs?
How do the variability in test conditions impact on repeatability/reproducibility of test result?
No. Only one condition (Φ3mm, speed of nail 0.1mm/s, nail angle 60 degrees).
We selected extreme condition within phase1 part1 condition.
We know these conditions should be discussed and decided with justification from now. But this test is just to confirm repeatability and reproducibility, so we selected conditions temporary.
We haven’t checked yet. It’s necessary to check.

24. Q(OICA)&A No Page Question Answer 4 -
Nail penetration testing is commonly performed by insertion perpendicular to the electrode planes. In this study, nail insertion is made from the top end of the cell and parallel to the electrode planes.
How does the direction of nail insertion affect the test results?
Should the direction of insertion be defined in the test method and how would this impact on feasibility of performing the test?
Now we are researching the influence of nail insert direction and position on test results at cell or module level.
If thermal runaway happens, not need to define direction (though it depends on the definition of thermal runaway).

25. Q(OICA)&A No Page Question Answer 5
What are the objective criteria for choice of target cell and how did you verify the appropriateness of selection criteria compared to other cell positions?
We selected target cell according to Phase1 part1 23B.3.5.
“For example, select the cell that is the nearest to the centre of battery casing or the cell that is surrounded by other cells which makes it difficult for the triggered cell to dissipate heat.”
In this sample there is a gap between modules and this sample has Al plates for cooling around modules. So we selected cell 5 considering that heat doesn’t diffuse through this.

26. Q(OICA)&A No Page Question Answer 6 15
Clarify explanation "difference in the way to open vent". Vent construction and functionality should be the same if identical test objects were used.
We are estimating tolerance of cell components (e.g. vent, electrode, etc.) may have impact on how to open vent. 7 -
How to apply acceptance criteria “egress” to component test. When is t=0, i.e. time of warning?
In component test, t=0 should be warning time though in our test, t=0 is voltage drop start time. 8
Interesting work but the study is too limited to verify repeatability/reproducibility of the trigger method, including all possible variations of test conditions.
We think so too. So we are going to keep researching and we need to conduct world round robin test. 9 16
Position displacement has significant impact on the severity of the trigger to initiate TR.
We think so too. We will check in this year.

27. Q(CANADA)&A No Page Question Answer 1 4
Depth –this will be dependent on cell positioning within pack,
Does nail stay inserted in pack (less reactive) or insert and release (more reactive)?
Nail stayed inserted pack during test. 2 5
Need to test multiple locations to confirm worst-case scenario. TP depends on heat transfer, and a thermal runaway in this location is surrounded by more thermal mass heat sinks, which may result in heating adjacent cells and a lower temperature overall. An edge cell, surrounded by air may transfer more of its energy to the fewer adjacent cells. It may also swell more before venting (less pack pressure), which may affect venting time and TP.
We selected target cell according to phase1 part1 this time (Near center and surrounded by other cells).
This sample has Al plate around module. We selected cell 5 considering that heat doesn’t diffuse through this.
We also think we need to discuss which cell should be selected as target cell.

28. Q(CANADA)&A No Page Question Answer 3 6
This will require knowledge of inner electrode construction,
Where does this information come from?
How does location accuracy of test affect outcome?
We got information of inner cell on internet this time.
Normally, OEM gives certification authority information like this.
We haven’t checked yet. 4 8
What does arrow mean?
Same as left. 5 9
Note: Temperature rise (next slide) of #2,4 is slower
Yes, temperature rise of #2, 4 is slower than the others.
It’s same as voltage drop.

29. Q(CANADA)&A No Page Question Answer 6 15
Would removing the nail after insertion help this?
A significant portion of heat released is through the mass transfer of venting gases (Work prepared by NASA using a battery calorimeter estimates up to 40% of the total energy).
The directionality of venting gases is an important consideration, but can be stochastic.
Nail was not removed during test. 7 18
Propagation could be dependent on cell choice, do you have plans for pouch cell testing?
Pouch testing will have more stochastic venting behaviors (no dedicated vent hole), that will certainly affect the repeatability of TP
We will conduct test using pack consists of pouch cell this year.

30. Q(Tesla)&A No Page Question Answer 1 12
We have also found enclosure pressure to be a reliable method of identifying thermal runaway in propagation testing
We think so too.
But there are some packs not sealed. For these, it’s difficult to measure pressure.

31. Pressure sensor

32. Conditions Voltage detection points
To detect thermal runaway of target cell and surrounding cells.
Module2 8 7 6 5
Cell 1 4 5 8 9 12
Target cell
（Cell5 in Module2）
Module1 2 3 4 2 3 6 7 10 11
Measurement Point
Remark V1
Voltage of module 1 V3
Voltage of module 3 V4
Voltage of module 4 V5
Voltage of module 5 V6
Voltage of module 6 V7
Voltage of module 7 V8
Voltage of module 8
Measurement Point
Remark
V2 1-3
Voltage of cell 1-3 inside module2
V2 4
Voltage of cell 4 inside module2
V2 5
Voltage of cell 5 inside module2
V2 6-7
Voltage of cell 6-7 inside module2
V2 8
Voltage of cell 8 inside module2
V2 9-12
Voltage of cell 9-12 inside module2

33. Conditions Thermocouple points
To detect thermal runaway of target cell and surrounding cells.
Module2
T2 4 8 7 6 5
Cell 1
T2 5 T8 T7 T6 T5 4 5 8 9 12
T2 8
Target cell
（Cell5 in Module2）
Module1 2 3 4 T1 T3 T4 2 3 6 7 10 11
T2 6
Measurement Point
Remark T1
Temp of module 1 T3
Temp of module 3 T4
Temp of module 4 T5
Temp of module 5 T6
Temp of module 6 T7
Temp of module 7 T8
Temp of module 8
Measurement Point
Remark
T2 4
Temp of cell 4 inside module2
T2 5
Temp of cell 5 inside module2
T2 6
Temp of cell 6 inside module2
T2 8
Temp of cell 8 inside module2

34. Conditions Thermocouple points
To detect thermal runaway of target cell and surrounding cells.
Module2
T2 4
Cell 1
T2 5 4 5 8 9 12
T2 8
Target cell
（Cell5 in Module2） 2 3 6 7 10 11
T2 6

35. Procedures REESS preparation Test preparation No Procedure 1
Remove REESS from vehicle. 2
Remove upper case from REESS. 3
Remove plastic cover for insulation from REESS. 4
Make a hole in upper case (See Page 13) and plastic cover to pass nail. 5
Set thermocouples and voltage detection lines to REESS. 6
Set pressure sensor to upper case. 7
Set plastic cover to REESS. 8
Set upper case to REESS. 9
Charge REESS and adjust SOC.
Test preparation No
Procedure 1
Set a nail test equipment in the test booth without nail. 2
Set REESS to the nail test equipment. 3
Adjust position of REESS and nail to pass it through the hole. 4
Set nail to the nail test equipment.

36. Procedures Test No Remark 1
Start measurement temperature, voltage and pressure. 2
Start to move nail until 1/2 of cell height.
→ Internal short circuit / Thermal runaway 3
Observation 4
Stop measurement. 5
Wait until thermal event settles. 6
Remove upper case and plastic cover. 7
Observe REESS after test. 8
Discharge or deactivate REESS. 9
Waste REESS.

37. Results (Temperature of adjacent cell)2 3 6 7 10 11
Cell 1 4 5 8 9 12
Module2
－: Sample 1 (Institute A)
－: Sample 2 (Institute B)
－: Sample 3 (Institute B)
－: Sample 4 (Institute B)
Initiation cell