IllustrationLithium-ion batteries packed with equipment under IATA PI 966 Section II must be at 30% state of charge or less when a cell or battery exceeds 2.7 Wh. Wh equals rated Ah times nominal voltage. Section II still counts as dangerous goods. Confirm with your forwarder and the current DGR before shipping.
Prototype devices move between Shenzhen and the US during EVT and DVT, and a lithium battery in the box turns the shipment into a dangerous goods shipment. This is an engineering team's summary of two public sources. It is not legal advice or dangerous goods training. The IATA document says it is guidance only and should not be relied on as a source of regulatory compliance. It points to the paid Dangerous Goods Regulations (DGR) 67th Edition and the ICAO Technical Instructions 2025-2026 as the basis. Duobay does not certify shipments, and nothing here is a test result.
What do the sources say?
Each row is read from a source linked in the last column. The 49 CFR text was read through a reproduction by Cornell LII. Verify it against the official 49 CFR text before you rely on it. The IATA guidance is the 2026 revision.
| Topic | What it says | Where | Source |
|---|---|---|---|
| Wh rating | Rated capacity in Ah times nominal voltage. | This is the basis for the 100 Wh and 2.7 Wh checks. | IATA lithium battery guidance, as of October 31, 2026 |
| Small-battery limits | 20 Wh per lithium-ion cell and 100 Wh per lithium-ion battery. | 49 CFR 173.185(c)(1)(i). | Cornell LII reproduction of 49 CFR 173.185, as of October 31, 2026 |
| Package content with equipment | The minimum number of batteries needed to power the equipment plus two spare sets, 5 kg net, for air packages. | 49 CFR 173.185(c)(4). | Cornell LII reproduction of 49 CFR 173.185, as of October 31, 2026 |
| State of charge, packed with equipment (PI 966 Section II) | Cells and batteries above 2.7 Wh must be offered at 30% or less of rated capacity. Effective 1 January 2026. Above 30% they go under Section I, which needs State of Origin and State of the Operator approval. | IATA guidance, 2026 revision. | IATA lithium battery guidance, as of October 31, 2026 |
| State of charge, contained in equipment (PI 967) | 30% (or 25% indicated battery capacity) is strongly recommended as a transport safety measure. It is not mandatory. | IATA guidance. | IATA lithium battery guidance, as of October 31, 2026 |
| What Section II exempts | Some labelling, packing and documentation. The batteries are still dangerous goods. | IATA guidance. | IATA lithium battery guidance, as of October 31, 2026 |
| UN3481 package mark, PI 967 Section II | Not required with no more than two batteries contained in equipment in the package. Required with more than two. IATA states this in an answer about mobile phones. | IATA guidance. Confirm against the DGR text before applying it to your product. | IATA lithium battery guidance, as of October 31, 2026 |
How do you compute Wh?
Wh = rated capacity (Ah) × nominal voltage (V)
mAh to Ah: divide by 1,000Use the rated capacity and nominal voltage from the datasheet. The worked examples below were recomputed for this article.
| Nominal voltage | Rated capacity | Wh | What it means |
|---|---|---|---|
| 3.7 V | 0.3 Ah | 1.11 Wh | Under 2.7 Wh, so the 30% state of charge rule for packed-with batteries does not apply at this size. |
| 3.7 V | 1.0 Ah | 3.7 Wh | Over 2.7 Wh, so the 30% state of charge rule applies when the battery is packed with equipment. |
| 3.85 V | 5 Ah | 19.25 Wh | Under 100 Wh as a battery and under 20 Wh as a single cell. Compare each cell and the whole battery against its own limit. |
The voltage and capacity values are examples. Replace them with the values on your own datasheet.
Which rule applies to which sample?
This table combines only the rows above. The Wh column uses the 49 CFR 173.185(c)(1)(i) limits. The guidance cited here does not tie the IATA Section II scope to those limits, so confirm the Section II Wh limits in the DGR. Where the sources are silent, the cell says so.
| Wh (49 CFR 173.185(c)(1)(i) limits) | Packing | Instruction | Section | State of charge | Marks |
|---|---|---|---|---|---|
| 100 Wh or less per battery (20 Wh or less per cell) | Packed with equipment | PI 966 | Section II | Offered at 30% or less of rated capacity if above 2.7 Wh. Above 30% moves the package to Section I. | Check the DGR for marks. The IATA guidance cited here does not state them for this row. |
| 100 Wh or less per battery (20 Wh or less per cell) | Contained in equipment, two batteries or fewer | PI 967 | Section II | 30% (or 25% indicated capacity) is recommended. It is not mandatory. | UN3481 mark not required, per the IATA phone example. |
| 100 Wh or less per battery (20 Wh or less per cell) | Contained in equipment, more than two batteries | PI 967 | Section II | 30% (or 25% indicated capacity) is recommended. It is not mandatory. | UN3481 mark required, per the IATA phone example. |
| Over 100 Wh per battery or over 20 Wh per cell | Any | Outside the small-battery limits in 173.185(c)(1)(i) | Not covered by this article | Not covered by this article. | Go to the DGR and your forwarder before you plan the shipment. |
Sources for this table: IATA lithium battery guidance and 49 CFR 173.185, as of October 31, 2026.
What are the common traps?
These follow from the source text above. They come from engineering reasoning about how the rules read. None describes an incident at any company.
- Using the UI percentage as the state of charge. The rule is written in terms of rated capacity. A gauge estimate is a software reading, and the guidance does not say it equals 30% of rated capacity. Measure charge directly.
- Applying the packed-with rule to an installed battery, or the reverse. The 30% limit is mandatory above 2.7 Wh for PI 966 Section II and only recommended for PI 967. A team that prepares every sample the same way avoids this mix-up. A team that reads one rule for both can miss a mandatory limit.
- Assuming Section II means "not dangerous goods". IATA states that Section II batteries are still dangerous goods and that only some labelling, packing and documentation is exempt.
- Counting only the pack and skipping the cells. The 173.185 limits are 20 Wh per cell and 100 Wh per battery. A pack can sit under 100 Wh while a cell in it does not meet the cell limit.
- Generalizing the UN3481 answer. IATA gives the two-battery threshold in an answer about phones. Without the DGR text, treat it as an example for phones. Check the DGR text for your product.
- Using an old edition. The 30% rule took effect on 1 January 2026. Check which DGR edition your forwarder works from before each shipment. A shipment prepared from last year's checklist can be out of date.
- Counting spare batteries without a limit. The text in 173.185(c)(4) caps an air package at the minimum number needed to power the equipment plus two spare sets, within 5 kg net.
What should you check on your own samples?
We have not measured any device for this article, and no result appears in it. These are checks to run yourself and with your forwarder. Set each pass line from your product requirements and the forwarder's written answer, and record the basis for it.
| What to test | How to instrument or collect | Raw data to record |
|---|---|---|
| Wh rating of each battery and cell | Read the rated capacity and nominal voltage from the cell datasheet and the pack label. Multiply. Do the same for each cell and for the whole pack. | Datasheet values, the label text, the multiplication, and which document each value came from. |
| Actual state of charge at pack time | Measure delivered charge with a coulomb counter or a controlled discharge test on a unit from the same build. Do not use the UI percentage as the measurement. | Rated capacity used, measured charge, the method, instrument and its calibration date, and the date and time. |
| How the fuel gauge reads at your target charge | Compare the gauge reading with the measured charge at several points on the same unit and on a second unit. | Gauge reading and measured charge side by side, firmware version, and temperature. |
| Charge held during the transit window | Charge to your target, seal, and re-measure after a rest period that matches your planned transit time. | Charge before and after, the rest duration, storage temperature, and whether the device was powered off or in shipping mode. |
| Device behavior at low charge | Boot and run the sample from your target charge. Confirm the receiving team can still power on and update firmware. | Boot result, any low-battery lockout or brownout, and the firmware log. |
| Marks and paperwork against the forwarder | Send the forwarder your draft package description, Wh figures, battery count and photos of the marks. Ask in writing what the carrier requires. | The question, the answer, the date, who answered, and any carrier-specific variation they name. |
Whether a particular carrier or forwarder accepts a given sample is something only they can tell you. Vendors of fuel gauges and cells may publish accuracy figures, but if yours does not, treat it as unpublished by the manufacturer and measure it on your own board.
What should you ask before you ship?
- What is the Wh rating of each cell and of the whole battery, and which document states the capacity and voltage?
- Is the battery packed with the equipment or contained in it, and does that change the packing instruction we follow?
- Do we know the state of charge of this build from a measurement, and what instrument did we use?
- How does the device behave at that charge when the recipient powers it on?
- How many batteries are in each package, and does that change the mark?
- Which DGR edition does our forwarder work from, and does the carrier add its own variation?
- Who at our company or at the forwarder holds the dangerous goods training that the shipment requires?
- Where in the package is the Wh figure written so an inspector can find it?
Questions about shipping battery samples
What is the Wh rating of my battery?
IATA defines it as the rated capacity in ampere-hours times the nominal voltage. A 3.7 V, 1.0 Ah cell is 3.7 Wh. Read both numbers from the cell datasheet (IATA guidance, as of October 31, 2026).
Do I have to ship prototype samples at 30% charge?
For lithium-ion batteries above 2.7 Wh packed with equipment under PI 966 Section II, yes, per the IATA guidance effective 1 January 2026. For batteries contained in equipment under PI 967, 30% is strongly recommended. It is not mandatory. Confirm which one applies with your forwarder.
Is Section II a way around dangerous goods rules?
No. IATA states that Section II batteries are still dangerous goods. Section II only exempts some labelling, packing and documentation.
Will a carrier accept my sample?
This article cannot say. Acceptance depends on the carrier and forwarder, and airlines can apply their own stricter variations. Ask in writing before you pack.
Is this legal advice?
No. This is an engineering team's summary of the sources linked below. It does not constitute legal advice or dangerous goods training. Tell us about your device if you want to discuss what your build needs.
If you want help planning EVT and DVT builds for your device, tell us about your device. You can also read how our gates work from feasibility to small batch.
Sources
All pages accessed October 31, 2026. This is an engineering summary. It is not legal advice. Re-check the current DGR edition before every shipment.
- IATA, Lithium battery guidance document (2026 revision): https://www.iata.org/contentassets/05e6d8742b0047259bf3a700bc9d42b9/lithium-battery-guidance-document.pdf (accessed 2026-10-31)
- 49 CFR 173.185, as reproduced by Cornell LII: https://www.law.cornell.edu/cfr/text/49/173.185 (accessed 2026-10-31)
Planning a device like this? Tell us what it needs to do. A Duobay engineer replies within 1 business day. Send a project brief →