UN Informal Working Group Meeting on Lithium Battery Tests

Ideas to Address Problems Testing Large and Small Cells and Batteries

George A. Kerchner Executive DirectorPortable Rechargeable Battery Association

November 11-13, 2008Washington, DC

Problems with Tests

Not updated in 8 years Do not take into account changes in

technology, applications and experience Inconsistent interpretations of UN testing

requirements and terminology More harmonization needed with terminology found

in international standards (e.g., IEC) Impractical to test large batteries (e.g., for

HEV) to the same criteria as small batteries (e.g., for PC)

New Design Type – UN Manual Section 38.3.2.1

Lithium cells or batteries which differ from a tested type by: (a) A change of more than 0.1 g or 20% by

mass, whichever is greater, to the cathode, to the anode, or to the electrolyte; or

(b) A change that would materially affect the test results,

shall be considered a new type and shall be subjected to the required tests.

Changes to 38.3.2.1 for Rechargeable Cells and Batteries

Cells or batteries which differ from a tested type by: (a) for primary cells and batteries, a change of

more than 0.1 g or 20% by mass, whichever is greater, to the cathode, to the anode, or to the electrolyte;

(b) for rechargeable cells and batteries, a change in Watt-hours of more than 20% or an increase in voltage of more than 20%; or

(c) a change that would materially affect the test results,

shall be considered a new type and shall be subjected to the required tests.

Small and Irregular Shaped Cells and Batteries

Vibration and shock tests require three mutually perpendicular mounting positions of the cell or battery

Difficult to define 3 distinct planes for very small and irregular shaped cells and batteries

Variation needed in sections 38.3.4.3.2 (vibration test procedure) and 38.3.4.4.2 (shock test procedure)

Variations also may be needed in other testing requirements

Mass Loss in Thermal Test – Section 38.3.4.2

Mass loss may occur due to material used in the battery

Mass loss should only be attributable to cell Amend mass loss definition –

“Mass loss means a loss of mass from cells that exceeds …. “

Impact Test on Component Cells From Batteries

Component cells testing noted only in Test 6 (Impact test) – Section 38.3.3(c)(ii) and (c)(iv)

What is intent? UN Model Regulations, IMDG Code and ICAO

TI require that cells or batteries be subject to UN tests

Add a clarifying “Note” under component cell definition similar to Note under current battery definition

UN Manual of Tests and Criteria “Cell” definition, Section 38.3.2.2 Cell means a single encased electrochemical unit (one

positive and one negative electrode) which exhibits a voltage differential across its two terminals. Under these Regulations, to the extent the encased electrochemical unit meets the definition of "cell" herein, it is a "cell", not a "battery", regardless of whether the unit is termed a "battery" or a "single cell battery" outside of these Regulations.

Testing Single Cell Batteries

Testing Single Cell Batteries

If cell is tested, is it really necessary to re-test single cell battery for classification purposes?

Large Lithium Batteries

More realistic definition needed for large and small batteries

Impractical to test large batteries and assemblies (e.g., HEV) to same criteria as small batteries (e.g., PC)

UN vibration and shock tests problematic for large batteries

Modifications to shock and vibration tests needed to account for large batteries and assemblies

Large Lithium Battery Definition

Current: > 6200 Wh for Lithium ion and > 500 g for Lithium metal

Recommended: > 600 Wh for Lithium ion and > 80 g for Lithium metal

Takes into account current technologies, applications and experience of automobile and battery manufacturers

Large Lithium Battery Testing

Cost is a major factor when testing large rechargeable batteries

24 rechargeable batteries currently required for testing Reduced to 16 in 2011 as a result of decision on PRBA

proposal at July UN meeting

8 large rechargeable batteries is sufficient for classification purposes

Same number (8) currently required for primary batteries

“Large” Battery Assembly Testing

UN-tested lithium batteries electrically connected to form a battery assembly with more than 500 g or 6200 Wh

Assembly does not require testing if - Equipped with a system capable of monitoring

the battery assembly and preventing short circuits, or over discharge between the batteries in the assembly and any overheat or overcharge of the battery assembly

“Small” Battery Assembly Testing

(< 500 g Li Metal or 6200 Wh) Test one (1) battery assembly in a fully

charged state under Tests 3, 4 and 5, in addition, Test 7 in the case of rechargeable battery assemblies

Rechargeable battery assemblies must be cycled at least 25 times

Assembly must be comprised of cells and batteries that have passed required UN tests

Vibration Test – T3

Current vibration test parameters based on transportation of small cells and batteries

Parameters do not realistically apply to larger batteries

Example: HEV battery systems are assemblies of electronic controllers, sensors, air flow ducts, cabling, cell mounting fixtures, cells, trays, covers and attachment brackets

Amend Vibration Test

Amend vibration tests for batteries > 600 Wh or 12 kg For Large batteries or batteries exceeding 12 kg,

the logarithmic frequency sweep is as follows: from 7 Hz a peak acceleration of 1 gn is maintained until 18 Hz is reached. The amplitude is then maintained at 0.8 mm (1.6 mm total excursion) and the frequency increased until a peak acceleration of 2 gn occurs (approximately 50 Hz). A peak acceleration of 2 gn is then maintained ….

Shock Test – T4

Shock values do not realistically apply to larger batteries

“Small” cells and batteries subject to a half-sine shock of peak acceleration of 150 gn and pulse duration of 6 milliseconds

“Large” cells and large batteries subject to a half-sine shock of peak acceleration of 50 gn and pulse duration of 11 milliseconds

Amend Shock Test

Testing of HEV-type battery packs at 150 gn is impractical

Recommend limiting acceleration to 50 gn for batteries > 600 Wh or 12 kg

Overcharge Test – T7

Batteries (modules) used to construct battery assemblies frequently designed without overcharge protection

Not designed to be or expected to be charged independently by anyone other than the manufacturer

Not possible to conduct Overcharge test on batteries (modules) because electronic overcharge protection is designed into battery assembly

Amend Overcharge Test

Amend Section 38.3.3(d) by adding following provision: “Batteries not equipped with overcharge

protection that are designed for use only in a battery assembly, which affords such protection, are not subject to the requirements of this test.”

Interpretations

No defined mechanism for official interpretations Should there be a UN guidance manual on lithium

battery testing requirements? How do interpretations get circulated or

distributed internationally? Should there be an annual meeting of “experts”

on lithium batteries similar to UN experts on explosives?

Harmonization with terminology in international standards would provide for more consistency