EVS-GTR TF5 Update Progress

TF5 task force – thermal propagation2015/6/4

China: Thermal propagation test is important to be considered in GTR, It’s necessary to discuss the test method of battery both in cell and pack level;.

Japan: 1.Manufacturing failures are considered as main causes of the internal short circuit; 2.Internal short circuit is one of the potential causes of fire hazard of Li-ion battery; 3.Manufacturing failures will not be completely eliminated in theory, and the BMS

will not prevent the internal short circuit caused by cell manufacturing quality control.

4. we should assess that all occupants can safely escape even if the internal short circuit of a cell occurs.

OICA: The vehicle safety can be assured by the safety design of battery pack BMS; the occupants have enough time to escape if the objective of propagation test is for vehicle safety.

F2F meeting in Beijing (May 12th)

TF5 discussed the thermal propagation issues on Jun 3th morning, and

TF5 had the following conclusion:

1.All parties of TF5 agree the importance of the battery thermal

propagation;

2. the definition of thermal propagation need to be discussed;

3. The cause of thermal propagation need to be discussed.

4. How to initiate the battery thermal propagation is the open issue.

F2F meeting in Washington (June 3rd)

1.USA will go on research of the method of initiating the battery thermal

propagation from the all the levels (i.e. cell/module/system?) ;

2.Japan will propose the thermal propagation definition；

3.OICA will provide more evidence explaining that the safety design of

vehicle level can avoid thermal propagation, and can give occupants enough

time to escape when the thermal propagation occurs；

4. China will organize one or two TF meetings to conduct more efficient

discussion about thermal propagation.

Next step work(proposal)：

Thanks！

Research result of thermal propagation test

From Japan

Nail pick Partial heating Nail penetration

AVoltage drop(V)(1h later) 0.32 0 Max→0

Cell temperature( ) (1h later)℃ 44 192

Phenomenon Nothing Smoke

BVoltage drop(V)(1h later) 0.12 0 0.41

Cell temperature( ) (1h later)℃ 30 119

Phenomenon Nothing Smoke

C

Voltage drop(V)(1h later) 0.04 Max→0

Cell temperature( ) (1h later)℃ 45 634

Phenomenon Nothing SmokePropagation

Research result of thermal propagation test

From USA

The following methods were tested:a. Conductive heating: cells wrapped in Nichrome wire.b. Mechanical damage: nail penetration.c. Conductive heating: hand-made film heater.d. Conductive heating: off-the-shelf film heater.e. Conductive heating: multiple off-the shelf film heaters.f. Conductive heating: thick film resistor.

See the document of EVS-06-35e.

Research result of thermal propagation test From Korea

Thermal runaway trigger should be internal short circuit test. Alternative test method of ceramic nail with metal tip can be applicable on module level for propagation test purpose.

Test item Test condition Drawbacks

Heating400W heater within the cellsHeating until thermal runaway

Heating powerSeverity of thermal runaway heating temperature ∝Max temp. 1/cell size (constant heater power)∝ Difficult to specify heater power for various cell design

Overcharge 1cell overcharging - 1C charging until thermal runaway

Usually multiple cells are exposed in overcharge condition.Not applicable for cells with overcharge protection.

Internal shortCeramic nail with metal tip - Test on single cell in module - Test condition : same with cell level ceramic nail test.

Same issues with cell test. - Case weakening. - Precision control (less than 5mV).

<Schematic>

Research result of thermal propagation test

From China

Test items Overcharge Nail HeatThermal runaway

temperature 300℃ 100℃～ 400℃ 250℃

Test result Venting and leakage Smoke or fire Most serious, Venting and leakage or fire

Operational Better normal GoodSuccessful Good normal Better

Influence factors Active Protection device, like PTC or CID Material Thermal diffusion

The test method of overcharge be applicable for the thermal runaway initiation of a single cell for thermal propagation test.