Interpretation Response #25-0021

Below is the interpretation response detail and a list of regulations sections applicable to this response.

Interpretation Response Details

Response Publish Date: 06/26/2025

Company Name: Currie Associates

Individual Name: Frank Lopez

Location State: NY Country: US

View the Interpretation Document

Response text:

June 26, 2025

Frank Lopez
Regulatory Compliance Specialist
Currie Associates
101 Ridge Street Suite I
Glens Falls, NY  12801

Reference No. 25-0021

Dear Mr. Lopez:

This letter is in response to your February 18, 2025 email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the transportation of lithium ion cells and batteries. Specifically, you ask several questions regarding the use of firmware (i.e., the software that controls the hardware of an electronic device) to limit the nominal energy expressed as the Watt-hour (Wh) rating of a lithium ion cell or battery contained in equipment. You present the following scenarios:

1. A lithium ion cell is capable of exceeding 20 Wh or a lithium ion battery is capable of exceeding 100 Wh, but the cell or battery firmware limits the nominal energy of the cell or battery to 20 Wh or 100 Wh, respectively.

2. A lithium ion cell is capable of exceeding 20 Wh or a lithium ion battery is capable of exceeding 100 Wh and is contained in equipment, but the cell or battery firmware limits the nominal energy of the cell or battery to 20 Wh or 100 Wh, respectively.

3. A lithium ion cell is capable of exceeding 20 Wh or a lithium ion battery is capable of exceeding 100 Wh and is contained in equipment, but the equipment's software limits the nominal energy of the cell or battery to 20 Wh or 100 Wh, respectively.

4. A lithium ion cell is capable of exceeding 20 Wh or a lithium ion battery is capable of exceeding 100 Wh and is contained in equipment, but the cell or battery firmware limits the nominal energy of the cell or battery to 20 Wh or 100 Wh. Furthermore, the cell or battery firmware is designed such that the end user can modify the cell or battery voltage to full capacity, exceeding 20 Wh or 100 Wh, respectively.

We have paraphrased and answered your questions as follows:

Q1. May the lithium ion cell or battery described in Scenario 1 be shipped in accordance with the smaller lithium ion cell and battery provisions in § 173.185(c)?

A1. Yes. The United Nations Manual of Tests and Criteria (UNMTC) (incorporated by reference, see § 171.7), subsection 38.3.2.3, defines nominal energy or Watt-hour rating as "the energy value of a cell or battery determined under specified conditions and declared by the manufacturer..." Firmware that controls the voltage and ultimately the nominal energy is within the design and specified conditions of the lithium ion cell or battery manufacturer. Therefore, the lithium ion cell or battery—as described in Scenario 1—can be considered a smaller lithium ion cell or battery for transportation.

Q2. May the lithium ion cell or battery contained in equipment described in Scenario 2 be shipped in accordance with the smaller lithium ion cell and battery provisions in § 173.185(c)?

A2. Yes. See answer A1. The lithium ion cell or battery contained in equipment—as described in Scenario 2—can be considered a smaller lithium ion cell or battery for transportation.

Q3. May the lithium ion cell or battery contained in equipment described in Scenario 3 be shipped in accordance with the smaller lithium ion cell and battery provisions in § 173.185(c)?

A3. No. In Scenario 3, the software that limits the lithium ion cell or battery nominal energy to 20 Wh or 100 Wh, respectively, is not inherent to the battery itself. Therefore, the lithium ion cell or battery manufacturer’s declared nominal energy value for the lithium ion cell or battery must be used when determining the applicability of the small lithium ion cell and battery provisions in § 173.185(c).

Q4. May the lithium ion cell or battery contained in equipment described in Scenario 4 be shipped in accordance with the smaller lithium ion cell and battery provisions in § 173.185(c)?

A4. Yes. See answer A1. The lithium ion cell or battery contained in equipment—as described in Scenario 4—can be considered a smaller lithium ion cell or battery for transportation. However, PHMSA notes that any modification to the lithium ion battery firmware that increases the Wh rating or nominal voltage by 20 percent or more or any modification that represents a change that would lead to failure of any of the tests specified in the UNMTC Section 38.3 (incorporated by reference, see § 171.7), constitutes a new lithium battery type that must be tested prior to any further transportation—see § 173.185(a)(1) and UNMTC 38.3.2.2. In addition, the lithium ion cell or battery’s marked Wh rating must be updated to reflect the new, higher Wh rating before any further transportation in commerce of the lithium ion cell or battery.

Q5. If the lithium ion cell or battery firmware limits the Wh rating of the cell or battery as described in Scenarios 1 through 4, should the cell or battery be marked with the Wh rating as limited by the firmware or the maximum possible nominal energy for the cell or battery?

A5. For Scenarios 1, 2, and 3, the lithium ion cell or battery must be marked with the Wh rating determined under the manufacturer’s specified conditions—i.e., as limited by the lithium ion cell or battery firmware (note – not the device’s software for Scenario 3). For Scenario 4, the lithium ion battery must be marked with the Wh rating allowed by the currently operative firmware before transportation in commerce or as specified in A4, the new, higher Wh rating for the new lithium battery type before any subsequent transport in commerce. Please note that in each scenario, the lithium battery test summary must indicate the Wh rating appropriate to the cell or battery. For Scenario 4, this could require an update to reflect the higher Wh rating resulting from firmware updates.

I hope this information is helpful. Please contact us if we can be of further assistance.

Sincerely,

Dirk Der Kinderen
Chief, Standards Development Branch
Standards and Rulemaking Division

§ 171.7, § 173.185(a)(1), § 173.185(a)(5), § 173.185(c)

Regulation Sections