EVS
Session 6 | Seoul | 18-20 Nov 2014
Agenda Item 9. Development of the draft GTR: Report from Task Force No. 5 and 6

Task Force 5 – cell/module/system test:
Dr. Xiao, as TF leader l, reported on the progress of TF5 including the Chinese proposal for three test procedures on nail penetration, oven, and crush test at the cell/module level.

OICA made its comment that inclusion of a nail penetration test in a regulation may create a technical barrier for the high density battery at the cell level.

The US representative also suggested TF5 to think about penetration test as vehicle level propagation test, and cell level penetration test can be kept as research item for design and product development. For the crush test, the US will prepare its result data from their research as soon as possible. The US would like TF5 to show the safety correlation at the cell level test to the safety at the vehicle level.

Answering the Canadian proposal to use the penetration test to check the integrity of the cell/module/system external casing, OICA expressed its opinion that the objective of the penetration test is not to simulate a crash worthiness test (i.e. simulating an object penetrating into the REESS), instead it simulates an internal short circuit event in the REESS.

Japanese delegation also mentioned that cell level penetration test is important while it is not directly related to vehicle safety. Since we are discussing vehicle safety regulation, how to combine cell level test into the GTR framework should be discussed further.

TF5 leader has agreed to have vehicle level propagation test as vehicle homologation test, but still believes the necessity to have cell level test to increase the battery safety which contributes to the whole vehicle safety level as a result. TF5 leader also rationalised that while there is still no way to stop the propagation once a fire has started within the REESS at cell level, then the test must require that no fire occurs at the incident. The best way to increase safety level can be the combination of cell level test and system level test.

OICA commented that all three tests have less influence to avoid the internal short circuit within the REESS since it is the quality control issue.

The chairperson commented that the internal short circuit incident is a serious phenomenon so that avoiding it is the first priority.

The US representative commented that the propagation issue is the most important since we cannot control internal short circuit perfectly for the time being.

Japanese delegation agreed with USA and emphasised that the main cause of internal short circuit comes from manufacturing error and not design error, so that it is very hard to detect future risk of production error by cell level homologation test with few cell representing all cells.

Japanese delegation, Mr. Fukuzawa made a presentation on propagation including their study results. He explained that the safety of the vehicle will be secured at vehicle level assuming that cell level incidents are unavoidable for the time being.

OICA had a question whether this system level test can solve all the incidents in the market, so they prefer having reliable warning system for the driver in the case of a thermal incident, to focus on keeping the driver and the occupants safe and minimise the risk and damage caused by thermal incident. Case scenario can be discussed technically and taken into consideration.

Dr. Xiao, as representative of China, made the presentation for the propagation study of China.

OICA representative commented that homogeneous heating is not representative of a realistic failure mode and that conducting a cell level testing magnifies the risk, questioning the necessity of the crush test at the cell level because there are already more representative tests at vehicle and/or system level. Because the technology of lithium-ion battery has not fully matured, OICA stressed the importance of research of thermal runaway and propagation in more depth.

US explained its stance towards propagation, admitting there is no correlation between the cell and system levels, yet testing at both levels is unavoidable for the time being and the phenomenon and mechanisms are very different by the type of REESS, and it is a response functional issue. All the research is not completed yet. Initiation of the thermal propagation is the key.

Japan agreed about the importance of initiation of the thermal propagation and to establish the certain way of that is very important even Japan itself has not finished its study yet.

The EVS IWG asked the TF5 leader to come back with a clear definition of internal short circuit including its risk, how to improve the safety of occupants in the vehicle, and its correlation with propagation phenomenon.

Since new tasks of TF5 are to define the internal short circuit and thermal propagation all the current proposals from TF5 (initial three tests proposals) was withdrew for further discussion.
The TF5 leader was asked to develop a meeting plan and to invite as many as interest experts as possible due to the importance of this task. The US (NHTSA) in particular has been requested to participate actively.

Task Force 6 – state of charge:
Dr. Kawai, as the leader of TF6, provided a status report of the task force. He expects to conclude TF6 task team activity at its next face to face meeting expected in early next year if agreement is reached for the actual text proposal for SOC setup test protocol.

The US participant questioned how 50% range of SOC was decided. He also recommended to use a more technically correct wording to explain the SOC. US will join the discussion of TF6 and provide data from the US research.

OICA answered that the manufacturers can show the vehicle SOC operating range and its limit, and it helps being accountable and fair. It varies by a REESS type and manufacturer and it is very difficult to define one single number, test protocol, type of vehicle for the time being.

During the last face-to-face meeting, the TF6 leader drafted a new proposal for SOC. TF and IG members are invited to provide their comments on this proposal by the end of December 2015.

The EVS IWG asked TF6 to prepare a proposal for the draft GTR by next EVS meeting in 2015.

Documentation
EVS-06-10 | Status report of the Electric Vehicle Safety GTR Task Force No. 5 (Cell/Module/System Test Requirements)
EVS-06-11 | Status report of the Electric Vehicle Safety GTR Task Force No. 6 (State of Charge)
EVS-06-17 | Presentation on the progress of the EVS Task Force 6 (State-of-Charge)