Download Proposal on T-6 Impact Test

ST
UNITED
NATIONS
Distr.
GENERAL
Secretariat
ST/SG/AC.10/C.3/2009/
20 – 22 April 2009
Original: ENGLISH
COMMITTEE OF EXPERTS ON THE TRANSPORT OF
DANGEROUS GOODS AND ON THE GLOBALLY
HARMONIZED SYSTEM OF CLASSIFICATION
AND LABELLING OF CHEMICALS
Sub-Committee of Experts on the
Transport of Dangerous Goods
Lithium Battery Information Working Group
Paris, France. 20 – 22 April 2009
Item b) of the provisional agenda
PROPOSALS OF AMENDMENTS TO THE T-6 IMPACT TEST
OF THE MODEL REGULATIONS ON THE TRANSPORT OF DANGEROUS GOODS
(UN 3090) - Transport of Lithium Metal Batteries
(UN 3091) - Transport of Lithium Metal Batteries Contained in or Packed with Equipment
(UN 3480) - Transport of Lithium Ion Batteries
(UN 3481) - Transport of Lithium Ion Batteries Contained in or Packed with Equipment
Modifications to T.6: Impact Test Including
Addition of Crush Test Method for Coin and Button Cells
Transmitted by UN T-6 Task Group:
Co-leaders:
Members:
M. Babiak and L. Florence
M. Boolish, A. Crane, J. Hadley, V. Feng,
K. Imazawa
Introduction
At the Lithium Battery Working Group Meeting on November 11-13, 2008 in Washington D.C., several
organizations gave presentations of their experience conducting the UN T.1-T.6 lithium battery
transportation tests. The discussions that ensued resulted in general agreement that several of the tests
required a more thorough review to determine if revision to the current methods were necessary.
Included in those tests noted for consideration was the T.6 Impact test.
Proposals
According to the Model Regulations, the purpose of the impact test is to simulate an impact during
transportation. Pass criteria are no disassembly, no fire and no cell temperature above 170C. The team
recognized the history for inclusion of this test into the Model Regulations is somewhat convoluted.
The 2000 revision of the T.6 test seems to have morphed from its true intent of an internal short circuit
test to a physical impact test regardless of whether an internal short circuit is created. There were many
possible internal short circuit tests proposed, such as the US National Aeronautics and Space
Administration (NASA) blunt nail test and the nail penetration test. Unfortunately, there was not
enough time to evaluate these tests thoroughly as alternatives to the T.6 Impact test. The team
recommends that this discussion be left fluid for future considerations, particularly as these tests may or
may not create/simulate an internal short circuit.
Notwithstanding any of the above, the team concluded the T.6 test method should include more detail
on the test set up to improve the repeatability and reproducibility of the test. For example:



The size and material used for the bar, which rests on the sample, should be described in more
detail, as it may affect the results of the test.
The weight dropped on the bar should be dropped in a controlled manner so that it falls directly on
the bar in a consistent manner each time.
Details on how pouch cells are tested needs to be included. Although they are prismatic shaped,
they can be quite thin and it is difficult to get a controlled impact on their thin side.
In addition to adding details to the impact test method, there was concern that the current impact test
was not an effective test and unduly severe for coin and button cells. There was consensus within the
team that the flat plate crush test, found in IEC 60086-4 (Safety of Lithium Batteries), is a more
appropriate simulation of transportation conditions for these types of cells. The crush test also provides
for better control during testing of these smaller, thinner cells.
It can be difficult to control the bar position on small cells and even when impacted, a drop in voltage is
not always observed although the cells are typically completely destroyed as shown in the pictures
below.
CR2032 Cells (20 x 3.2 mm)
After Impact Test
ML414 Cells (4.8 x 1.4 mm)
Before and After Impact Test
With the flat plate crush test, however, even though the cells are also destroyed, an internal short
circuit is routinely observed. The chart below shows the voltage profile for a CR1620 cell during the flat
plate crush test. This profile is also representative of other coin cell types and sizes.
The Impact test also occasionally creates a spark during testing when the metal bar is quickly forced into
the lithium coin battery. This spark, on occasion, can ignite the electrolyte within the cell and lead to a
failure of the sample, even though there was no excessive temperature rise or fire from internal short
circuit. This is clearly not the intent of the impact test. In the unlikely event of an impact during
transportation, the impact would occur within the insulated packaging of the cells where no spark would
be created. A more controlled flat plate crush minimizes/eliminates the possibility of sparking from a
quick impact.
As noted in IEC 60086-4 Safety of Lithium Batteries:
NOTE For some cell designs, the crush test is a more appropriate simulation of an internal short-circuit
than the impact test. It is therefore provided as an alternative test method for this purpose.
A comparison of the existing T.6 and proposed revisions from the ad hoc team is shown below.
38.3.4.6
Proposals
Test 6: Impact/Crush
38.3.4.6.1 Purpose
38.3.4.6.1
Purpose
This test simulates an impact.
These tests simulate mechanical abuse from an impact
or crush.
38.3.4.6.2
38.3.4.6.2
38.3.4.6
Current Language
Test 6: Impact
Test procedure
Test procedure - Impact
The test sample cell or component cell is to be placed
on a flat surface. A 15.8 mm diameter bar is to be
placed across the centre of the sample. A 9.1 kg mass is
to be dropped from a height of 61  2.5 cm onto the
sample.
The test sample cell or component cell is to be placed
on a flat smooth surface. A 15.8 mm diameter, at least
12 cm long, Type 316 stainless steel bar is to be placed
across the centre of the sample. A 9.1 kg mass is to be
dropped from a height of 61 ± 2.5 cm at the
intersection of the bar and sample in a controlled
manner using a near frictionless, vertical sliding track or
channel with minimal drag on the falling mass. The
vertical track or channel used to guide the falling mass
shall be oriented 90 degrees from the horizontal
supporting surface.
A cylindrical or prismatic cell is to be impacted with its
longitudinal axis parallel to the flat surface and
perpendicular to the longitudinal axis of the 15.8 mm
diameter curved surface lying across the centre of the
test sample. A prismatic cell is also to be rotated
90 degrees around its longitudinal axis so that both the
wide and narrow sides will be subjected to the impact.
Each sample is to be subjected to only a single impact.
Separate samples are to be used for each impact.
A cylindrical, pouch, or prismatic cell is to be impacted
with its longitudinal axis parallel to the flat surface and
perpendicular to the longitudinal axis of the 15.8 mm
diameter curved surface lying across the centre of the
test sample. A prismatic cell is also to be rotated 90
degrees around its longitudinal axis so that both the
wide and narrow sides will be subjected to the impact.
Each sample is to be subjected to only a single impact.
Separate samples are to be used for each impact.
A coin or button cell is to be impacted with the flat
surface of the sample parallel to the flat surface and the
15.8 mm diameter curved surface lying across its
centre.
A coin or button cell is to be crushed in accordance with
38.3.4.6.3 rather than impacted.
38.3.4.6.3
Test Procedure – Crush
38.3.4 6.3 Requirement
A coin or button cell is to be crushed between two flat
smooth surfaces with the applied force to the coin cell
on the flat surfaces of the coin cell. The crushing is to be
gradual with a speed of approximately 1.5 cm / s at the
first point of contact. The crushing is to be continued
until the applied force reaches 13 kN. Each test cell or
component cell is to be subjected to one crush only.
38.3.4 6.4
Requirement
Cells and component cells meet this requirement if
their external temperature does not exceed 170 °C and
there is no disassembly and no fire within six hours of
this test.
Cells and component cells meet this requirement if
their external temperature does not exceed 170 °C and
there is no disassembly and no fire within six hours of
this test.