Discussion on Cell and Battery Size Limits in Special Provision 188

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Discussion on Cell and Battery Size Limits in Special Provision 188

Agenda item 1.6

Discussion on Cell and Battery Size Limits in Special Provision 188

Transmitted by theUnited States

Introduction and background

  1. The 1st Informal Working Group Meeting on Lithium Battery Tests raised a question concerning the size limit of a cell or a battery under UN Model Regulations Special Provision 188 (SP188), specifically noting that SP188 limits cells to a Wh rating of not more than 20 and batteries to a Wh rating of not more than 100. Because differing interpretations lead to inconsistent application and enforcement of the regulations, the Informal Working Group requested that the UN Sub-Committee advise on the issue from a competent authority perspective in order to issue a uniform interpretation about whether the 20Wh limit applies only to cells transported as cells or also to cells installed in a battery. The UN Sub-Committee discussed this question during its 47th session.The majority within the UN Sub-Committee was of the view that the specified cell and battery limits are intended to be applied independently.

Special Provision 188’s application to cell and batteries

  1. SP188 was developed consistent with the concept of limited quantities for other dangerous goods.Specifically, the rationale behind limited quantity provisions is that selected dangerous goods packed in relatively small quantities and in good, robust packaging pose a lesser risk in transport than do the same goods packed in larger volumes, and on this basis some relief from the standard requirements or alternative provisions may be accepted. In consideration of an appropriate size limit to apply within SP188, professional judgement and market assessment were the primary considerations because there were no criteria for assessing variable risk.This approach is consistent with the limited quantity provisions established for liquid and solid dangerous goods.
  2. Since batteries are considered articles, the limits in SP188 were applied to the manufactured article as presented for transport. Therefore, the limits were assigned for a cell when transporting a cell, and for a battery when transporting a battery. This is supported by the structure of SP188.
  3. Therefore, for the purpose of applying SP188,
  4. If the article as presented for transport meets the definition of a cell, then the limits in SP188(a) apply.
  5. If the article as presented for transport meets the definition of a battery, then the limits in SP188(b) apply.
  6. Further, both cells and batteries are defined terms. Therefore, for the purpose of applying SP188, if the shipper meets the definition of a cell then SP188 (a) applies. If the shipper meets the definition of a battery, then SP188 (b) applies. If meeting the definition of a battery, than the shipper no longer is shipping a cell and SP188 (a) does not apply. When requirements are applied to component cells within a battery, for example for testing purposes, the distinction is explicitly stated (see UN Manual of Test and Criteria 38.3.3(c) and (e)).
  7. This approach is clearly indicated by the size limitations established in the original SP188. The size limits in SP188 applicable to lithium ion batteries were originally measured in equivalent lithium content. The Model Regulations assigned separate limits for lithium ion cells and lithium ion batteries. Battery size limits were determined by adding the equivalent lithium content of the component cells.
  1. The term equivalent lithium content was previously defined in the UN Manual of Tests and Criteria as follows: Equivalent lithium content means, for a lithium ion cell the product of the rated capacity, in ampere-hours, of a lithium ion cell times 0.3, with the result expressed in grams. The equivalent lithium content of a battery equals the sum of the grams of equivalent lithium content in the component cells of the battery. Aggregate lithium content was also defined separately as the sum of the grams of lithium content or equivalent lithium content contained by the cells comprising the battery. Equivalent lithium content is calculated by multiplying the rated capacity of a cell in ampere-hours by 0.3. The equivalent lithium content of a battery is calculated by adding the equivalent lithium content of the component cells.
  1. In 2006, the UN Sub-Committee adopted a separate requirement that lithium ion batteries subject to SP188 be marked with the Wh rating on the outside case. The UN Sub-Committee imposed this requirement on batteries only and not on the cells contained in the battery. The purpose of the Wh rating on the outer casing of a lithium ion battery is primarily to aid in the recognition for down-stream shippers to the applicability of the SP188 provisions. If the UN Sub-Committee intended for component cells to meet certain size requirements when assembled in a battery, additional markings indicating the number and size of cells would be required. This further substantiates assessment that under current provisions the limit of 20 Wh per cell applies when lithium ion cells are offered for transport and the 100Wh limit applies when a lithium ion battery (composed of multiple cells) is offered for transport.

Recommendation

It is the opinion of the U.S. competent authority that the cell limits (20 Wh) and the battery limits (100 Wh) described in SP188 of the UN Model Regulations applyindependently. For a lithium ion battery, provided the battery does not exceed 100 Wh, the size limit in SP188 is met regardless of the size or number of the component cells.

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