UN/SCETDG/34/INF.XX

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UN/SCETDG/35/INF.XX

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

Thirty-fifth session

Geneva, June 2009

Item X of the provisional agenda

LISTING, CLASSIFICATION AND PACKING

Testing of Large Lithium Batteries and Lithium Battery Assemblies

Transmitted by the Council on the Safe Transportation of Hazardous Articles (COSTHA)

Introduction

1. Among COSTHA’s membership is a group identified as the North American Automotive HAZMAT Action Committee (NAAHAC). Participants in this committee include 12 automobile manufacturers from around the world but operate in the United States. Additionally, COSTHA counts five (5) additional members who are direct suppliers to the automotive industry, providing numerous materials and devices for production support.

2. The Sub-Committee has recognized the need to review the UN Manual of Tests and Criteria, specifically Section 38.3 as they relate to the transport of large lithium batteries and assemblies. COSTHA supports the efforts of the Sub-Committee in this endeavour and would like to present data to further the discussion.

Discussion

3. The concern over the testing in large format lithium ion batteries was discussed at length at the UN Informal Working Group on Batteries held 11 November to 13 November 2008. During this meeting, Delphi, a COSTHA member organization, provided a presentation detailing the concerns facing the gasoline-electric hybrid vehicle, hydrogen fuel cell hybrid-electric vehicle, and pure battery electric vehicle manufacturers and suppliers with regards to the testing of these “large” batteries. Specifically, the UN Test #3 was identified as one of the tests posing significant design issues for the battery manufacturers.

4. As detailed in ST/SG/AG.10/C.3/2008/46 submitted by PRBA, the UN Manual of Tests and Criteria Section 38.3 was originally conceived to test the safety of relatively small batteries designed to support consumer appliance or electronic devices such as cell phones, laptops, and portable tools. While the criteria was broad enough to include extremely large batteries (greater than 500g aggregate lithium content), the market for batteries between these uses was not yet realized.

5. Over the last 3 years, the environmental and economic climates have changed dramatically, ushering in a new wave of technologies that make hybrid and pure battery electric vehicles both physically and economically feasible. Lithium ion batteries that were once reserved for small applications will be available in the very near future for standard vehicles as well as all-terrain and street cycles.

6. Test 3 currently requires cells and batteries to be exposed to vibration. Specifically the test requires the battery to be mounted to a horizontal surface on the vibration machine and exposed to a sinusoidal waveform with a logarithmic frequency sweep from 7 Hz to 200 Hz and back to 7Hz in 15 minutes. The cycle is repeated twelve (12) times for a total of 3 hours. This test must be conducted on three (3) mutually perpendicular mounting positions. Additionally, as the frequency increases, the peak acceleration is also increased. From 7 Hz to 18 Hz, the acceleration is set at 1 gn. From 18 Hz to ~50 Hz, the acceleration is increased to 8 gn, then it is maintained at 8 gn as the frequency is increased to 200 Hz and reduced back to ~50 Hz. At this frequency, the acceleration begins decreasing to 1 gn as the frequency decreases to 18 Hz. Again, the acceleration is set at 1 gn from 18 Hz to 7 Hz.

7. Gasoline-hybrid vehicle battery assemblies typically range today between 14 kg and 80 kg with full-electric vehicle batteries often exceeding 100 kg mass. Their capacity is typically 300 Wh to 2,500 Wh for hybrid batteries and in excess of 5,000 Wh for full-electric vehicle batteries.

8. Unlike individual cells and batteries, vehicle battery assemblies include systems of electronic controllers, sensors, air flow ducts, cabling, cell mounting fixtures, cells, trays, covers, and attachment brackets. They are not “solid” materials like single cells or even small battery “packs”, but are instead a mechanical and electrical construct designed to withstand impact and vibrations encountered in a road vehicle. Because they are not solid, battery systems will have several resonant frequencies under 200 Hz which will magnify the vibration effects.

Applied Forces for Different Masses

9. Current Test 3 frequency and acceleration conditions are inappropriate for these hybrid or electric vehicle (HEV) battery assemblies and are not realistic in real world transport. Any vibrations encountered during transport would be damped due to the mass of the package. Vibration would not be transmitted directly to the pack due to the damping and isolation provided by the skid, pallet, and packaging.

10. Most importantly, the forces required for HEV battery assemblies during the testing are well beyond any forces that would be encountered during transport. In fact, if the current vibration testing was applied to a complete vehicle, the vehicle likely would not survive.

9. The force applied in the test to cell phone or laptop batteries is governed by the equation:

F=m*a

Where: F = force measured in Newtons (N),

m = mass measured in kilograms (kg),

a = acceleration measured in multiples of the constant gn, which equals 9.8 m/sec2 ,

The force applied from 18 Hz to 200 Hz in the vibration test of a cell phone or laptop battery (0.5 kg) at 8 gn is equal to approximately 39 N:

0.5 kg * 8 * 9.8 m/sec2 = 39.2N

10. The force applied in the test to HEV battery systems is governed by a different equation due to resonance:

F=m*a / 2ξ

Where: F = force measured in Newtons (N),

m = mass measured in kilograms (kg),

a = acceleration measured in multiples of the constant gn, which equals 9.8 m/sec2 ,

ξ = damping constant related to the absorption of energy by the battery assembly. For the purposes of this test, the damping constant is set at 0.04 based on testing similar designs.

11. When the masses of HEV batteries are used, the forces exceed 13,500 N for smaller hybrid batteries (1) and 78,000 N for larger hybrid batteries (2):

(1)  14 kg * 8 * 9.8 m/sec2 / (2*0.04)= 13,720N

(2)  80 kg * 8 * 9.8 m/sec2 / (2*0.04)= 78,400 N

These forces are three hundred and fifty (350) times and two thousand (2000) times the force required for testing cell phone or laptop batteries.

12. To provide a comparison and an understanding that these forces are very large and can not be generated during transportation. The force required to stop a 400 kg weight travelling at a speed of 30kph within 1 meter is 13,880 N. The force required to stop a 2200 kg weight travelling at a speed of 30kph within 1 meter is 76,400 N

13. The test is required to be conducted for 9 hours total, with more than 6 hours at the 8 gn peak acceleration.

14. If the same force applied during Test 3 on a laptop battery (39.2 N) were applied to a smaller hybrid battery (14 kg), the required acceleration would be 0.023 gn.

F = m * a / 2ξ

a = (F * 2ξ)/m

39.2 N * (2*0.04)/14kg = 3.136N/14kg

=0.224 m/sec2

=0.023 gn

Proposal

15. Although a thorough review of the waveform and frequency range may be warranted, COSTHA recommends reducing the required peak acceleration applied above18 Hz from 8 gn to 2 gn for large batteries (12 kg or greater). Far from reducing safety, a 2 gn acceleration would still apply a force of 2940 N to the battery assembly for greater than 6 hours of a 9 hour vibration test.

12 kg * 2 * 9.8 m/sec2 / (2*0.04) = 2,940N