Currie Associates, Inc. — Hazardous Materials Safety Interpretation

Page 1U.S. Department of Transportation Pipeline and Hazardous Materials Safety Administration February 5, 2026 Ana Diaz Regulatory Compliance Specialist Currie Associates, Inc. 101 Ridge Street Suite I Glens Falls, NY 12801 Reference No. 25-0102 Dear Ms. Diaz This letter is in response to your July 22, 2025 letter requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to size limits for lithium ion batteries with respect to exceptions for smaller cells or batteries and prior clarification provided in a previous letter of interpretation (Reference No. 15-0009).a You indicate that the definitions section in 38.3.2.3 of the Eighth Revised Edition of the United Nations (UN) Manual of Tests and Criteria (MTC) now defines a battery as “two or more cells or batteries which are electrically connected together and fitted with devices necessary for use...” Given this revised definition, you are seeking confirmation that: (1) a lithium ion battery consisting of two cells, each exceeding 20 watt-hours (Wh) but with a combined total of less than 100 Wh, qualifies for the exception outlined in § 173.185(c)(1)(i); and (2) the prior clarification remains valid. Yes, your understanding is correct. Furthermore, the letter of interpretation (Ref. No. 15- 0009) cited in your incoming letter remains valid. PHMSA can confirm that the 100 Wh limit applies to the assembled battery, and that the 20 Wh limit for individual cells does not need to be considered for the component cells within that battery. While it is accurate that the UN MTC has updated the definition of a “battery,” this revised definition does not invalidate the 2015 letter of interpretation. If the assembled battery’s total energy density is under 100 Wh, 1200 New Jersey Avenue, SE Washington, DC 20590 a Reference No. 15-0009#

Page 2the exceptions specified in § 173.185(c)(1)(i) apply, even if each component cell exceeds the 20 Wh limit. I hope this information is helpful. Please contact us if we can be of further assistance. Sincerely, Dirk DerKinderen Chief, Standards Development Branch Standards and Rulemaking Division#

Page 3Baker, Y. 25-0102 July 22, 2025 Mr. Matthew Nickels Acting Director, Standards and Rulemaking Division Pipeline and Hazardous Materials Safety Administration Attn: PHH-10 U.S. Department of Transportation East Building, 1200 New Jersey Ave., SE Washington, D.C. 20590-0001 Submitted: Via Email cc: infocntr@dot.gov Dear Mr. Nickels: Currie Associates would like to request a formal letter of interpretation regarding the standing interpretation of Letter of Interpretation (LOI) 15-0009. Specifically, we would like to confirm that the interpretation provided by the LOI 15-0009 regarding clarification on the size limits under the exception §173.185(c)(1)(i) for lithium ion batteries, applies to a lithium ion battery comprised of two cells that are greater than 20 Wh each, together forming a battery that is less than 100 Wh. Currie Associates requests this interpretation to confirm our understanding that the interpretation indicated in LOI 15-0009 is still valid given the progression in time and the updated definition for “battery” in the UN Manual of Tests and Criteria. Letter of Interpretation 15-0009 states: Section §173.185(c)(1)(i) states that the Wh rating may not exceed 20 Wh for a lithium cell or 100 Wh for a lithium ion battery. The United Nations (UN) Manual of Tests and Criteria defines a battery as “one or more cells which are electrically connected together by permanent means.” The 100 Wh size limit applies to your battery irrespective of whether the component cells exceed the 20 Wh rating for a cell. Therefore, the exceptions in §173.185(c)(1)(i) apply to your lithium ion battery configuration [81.4 Wh battery comprised of two individual 40.7 Wh cells] since the battery does not exceed 100 Wh. The UN Manual of Tests and Criteria has since updated the definition of “battery” to “two or more cells or batteries which are electrically connected together and fitted with devices necessary for use…” Based on the information provided in LOI 15-0009, §173.185(c)(1)(i), and the UN Manual of Tests and Criteria, Currie Associates understands that the size limits under the exception §173.185(c)(1)(i) for lithium ion batteries would include a lithium ion battery comprised of two 101 Ridge Street Suite I, Glens Falls, NY 12801 | Phone: 1-518-761-0668 | mail@currieassociates.com#

Page 4cells, each greater than 20 Wh, that form a battery that is less than 100 Wh; however, we would like an updated letter of interpretation to confirm that our understanding is correct. Currie Associates appreciates your review of this interpretation request, and we look forward to hearing from you soon. Sincerely, Ana Diaz Regulatory Compliance Specialist Currie Associates www.currieassociates.com ana@currieassociates.com O: 518-761-0668 101 Ridge Street Suite I, Glens Falls, NY 12801 | Phone: 1-518-761-0668 | mail@currieassociates.com Page 2 of 2#