TF5 – Status report on thermal propagation

EVS-GTR 9th IWG meetingChangchun, China

2015/9/17

Work proposal ( 8th meeting in Washington DC)

USA will go on research of the method of initiating the battery thermal runaway and propagation from all the levels (i.e. cell/module/system?) (before 2015-08-01);

Japan will propose the definition of thermal runaway and propagation and the criteria of thermal propagation (before 2015-08-01);

OICA will provide more evidence explaining that the safety design of vehicle level can avoid the thermal propagation, and can give occupants enough time to escape when the thermal propagation occurs, as well as the safety condition description between the single cell thermal runaway and the battery pack thermal propagation happening (before 2015-08-01);

China will organize one or two telecom TF meetings to conduct more efficient discussion on the thermal runaway and propagation (before 2015-08-15).

Work Progress - JapanDefinition and criteria on thermal runaway and propagation

Definition:

“Thermal runaway” means the phenomena of uncontrollable heat generation with continuous temperature rise caused by exothermal chain reaction in the cell.“Thermal propagation” means the sequential occurrence of thermal runaway within a battery system triggered by thermal runaway of a cell in that battery system.

Criteria:No evidence of fire or explosion by visible validation (Within 1 hour observation period since the test initiation).

Work Progress - JapanResearch of initiating thermal runaway and propagation

Research summary:Investigated appropriate initiation methods. For Prismatic cell: Nail; For Pouch cell: Partial heating.Suitable initiation method should be selected based on battery type and connecting structure.There are still remaining technical issues as mentioned below. 1) Applicability of initiation methods for all batteries. To confirm the applicability for the batteries other than tested devices. To justify the reason for choosing the initiation method for the battery. 2) Appropriateness as GTR. To consider the influence of actual processing for certification test. 3) Repeatability and reproducibility of tests.

Proposal:To ask TF5 to validate test methods for variety of batteries to establish test method as GTR.To request TF5 to address the technical issues as shown in above.

Work Progress - OICA

OICA gave response to the following 3 questions:

1)The safety design of vehicle level can avoid the thermal propagation

2)The safety design of vehicle level can give occupants enough time to

escape when the thermal propagation occurs

3)The safety condition description between the single cell thermal

runaway and the battery pack thermal propagation happening

Work Progress - China

Proposed initiation method and procedure on thermal runaway and propagation:

Let one cell thermal runaway to see if the battery pack can keep the

normal function for certain time before thermal propagation happens

Battery pack is fully charged

Heat a cell ( surrounded by other cells) with resistive wire or heating

plate until thermal runaway happening

Monitor for at least an hour

Criteria:

No fire, no explosion

Keep normal function for at least 5 minutes?

Next step work proposal

To provide the detailed test procedure and criteria of initiating thermal

runway and propagation for distribution and discussion (nail

penetration and partial heating), with the reason for heat rate

(100oC/min) , the material for nail, etc. (Japan) ( the end of

December?) To provide the detailed test procedure and criteria of initiating thermal

runway and propagation for distribution and discussion (heating), with

the definition of normal function (change to minimum function?)(China

also will do test on pouch type battery) ( the end of December?) To provide research report and draft procedure and criteria of initiating

thermal runaway and propagation. (US) ( the end of December?) To provide input to test procedure, criteria and relevant requirements.

(all TF5 members, such as the duration to keep minimum function,

escape time, etc.)

Thanks ！