Quick answer: Lithium batteries move as Class 9 hazardous materials under 49 CFR Parts 171 to 180. They ship under four UN numbers, UN3480 and UN3090 for batteries alone and UN3481 and UN3091 for batteries packed with or inside equipment. Every cell and battery must pass UN 38.3 testing and carry correct Class 9 marking, labeling, and trained-shipper documentation.
Lithium battery transport is the regulated movement of lithium-ion and lithium-metal cells and batteries, which the U.S. Department of Transportation classifies as Class 9 miscellaneous hazardous materials because a damaged or short-circuited cell can enter thermal runaway and ignite. If you build, buy, or move batteries, the rules that govern your freight sit in the federal Hazardous Materials Regulations (HMR), the international air and ocean codes, and the UN testing standard. This guide consolidates the compliance decisions a commercial shipper actually has to make, in the order you have to make them.
Getting it wrong is expensive. The Pipeline and Hazardous Materials Safety Administration reports that all lithium-ion batteries must now show a watt-hour rating on the outer case, a change that took effect on May 10, 2024 (PHMSA Lithium Battery Guide, 2024). A load that shows up mislabeled or undocumented gets refused, and the storage and redelivery costs land on the shipper.
Why lithium batteries are regulated as Class 9
Lithium batteries are regulated because they store a large amount of energy in a small package and can fail dangerously. A physical impact, an internal defect, overcharging, or an external short circuit can trigger thermal runaway, a self-sustaining chemical reaction that generates intense heat, flammable gas, and fire that standard extinguishers struggle to control. Aviation data shows the trend is real: UL Standards & Engagement recorded lithium-ion thermal-runaway events on U.S. flights at a rate of roughly twice per week in 2024, the second-highest annual rate in six years of tracking (UL Standards & Engagement, 2025).
That failure mode is why the rules exist and why they scale with energy content. The more energy a cell holds, the more testing, packaging, and documentation the regulations demand before it can move.
The four UN numbers for lithium batteries
Lithium batteries ship under one of four UN identification numbers, and picking the right one drives every downstream decision on packaging, marks, and papers. The split is by chemistry (ion versus metal) and by how the battery travels (alone versus with equipment).
- UN3480: Lithium-ion batteries shipped by themselves.
- UN3481: Lithium-ion batteries packed with, or contained in, equipment.
- UN3090: Lithium-metal batteries shipped by themselves.
- UN3091: Lithium-metal batteries packed with, or contained in, equipment.
Two more numbers matter in finished-vehicle logistics. UN3171 covers a battery-powered vehicle or equipment, the entry that applies when the battery is installed and driving the unit, and UN3536 covers lithium batteries installed in a cargo transport unit. All of these sit in Class 9, and the batteries themselves are not assigned a packing group, though fully regulated shipments require UN-specification packaging built to the Packing Group II performance level under 49 CFR 173.185 (PHMSA).
UN 38.3: the testing every cell and battery must pass
UN 38.3 is the design-qualification standard that proves a cell or battery can survive the physical stresses of transport, and it is a precondition for shipping any lithium battery. The standard, found in Section 38.3 of the UN Manual of Tests and Criteria, runs eight tests. A shipper does not perform these tests, but you are responsible for confirming the product passed and that a UN 38.3 test summary is available.
TestNameWhat it simulates
T.1
Altitude simulation
Low-pressure exposure of unpressurized air cargo
T.2
Thermal test
Rapid hot and cold cycling that stresses seals
T.3
Vibration
Transport vibration across three axes
T.4
Shock
Impact and rough handling
T.5
External short circuit
An accidental short at elevated temperature
T.6
Impact / crush
Internal short from mechanical damage (cells only)
T.7
Overcharge
Overcharge conditions (rechargeable batteries only)
T.8
Forced discharge
Deep or reverse discharge (cells only)
The document that proves this is the piece most shippers forget until a load is refused. Our companion guide on shipping damaged and defective lithium batteries covers what happens when a cell fails those design assumptions in the field.
Fully regulated or excepted? Use the watt-hour thresholds
Not every lithium battery carries the full Class 9 obligation, and the dividing line is energy content. Smaller cells and batteries ship as "excepted" with lighter requirements, while larger ones are fully regulated. The thresholds differ for lithium-ion (measured in watt-hours) and lithium-metal (measured in grams of lithium).
ChemistrySmall cellSmall batteryHighway/rail-only allowance
Lithium-ion
≤ 20 Wh
≤ 100 Wh
Cell ≤ 60 Wh, battery ≤ 300 Wh
Lithium-metal
≤ 1 g lithium
≤ 2 g lithium
Cell ≤ 5 g, battery ≤ 25 g
Read the table as a decision. First identify the chemistry. Then check the watt-hour or gram rating against the small-cell and small-battery limits. If the battery moves only by U.S. highway or rail, the higher domestic allowance applies, which is why a battery legal to truck may still be fully regulated by air. Batteries above these limits are fully regulated and require UN-specification packaging, the Class 9 label, shipping papers, and trained hazmat employees under the federal hazardous materials rules enforced by FMCSA.
The 30% state-of-charge rule, stated correctly
The 30% state-of-charge rule limits how charged a lithium-ion battery can be when it ships, but it does not apply to every mode, and most guides state it wrong. The cap applies to transport by cargo aircraft: lithium-ion cells and batteries must be offered at no more than 30% of rated capacity, under special provision A100 in the HMR (PHMSA, 2024).
U.S. highway and rail transport has no state-of-charge limit. If you move batteries by truck, the 30% figure does not restrict you. For air, the rule is tightening: effective January 1, 2026, the International Air Transport Association makes the 30% cap mandatory rather than recommended for certain ratings, including UN3481 batteries above 2.7 Wh (IATA Dangerous Goods Regulations). Knowing which mode you are booking prevents both over-compliance that slows freight and under-compliance that gets it refused.
Marking, labeling, and documentation
Marking and labeling tell every handler what is inside the box and how to respond if it fails, and the requirements track the fully-regulated versus excepted split above.
Fully regulated shipments need the Class 9 lithium battery hazard label, the UN number and proper shipping name, hazmat shipping papers with emergency-response information, the Cargo Aircraft Only label where applicable, and hazmat employees trained under 49 CFR 172.704. Smaller excepted batteries need the lithium battery mark, the rectangular red-hatched-border mark that must measure at least 100 mm by 100 mm, showing the UN number. PHMSA notes that the contact-telephone-number element of that mark is being phased out on December 31, 2026 (PHMSA, 2024). Since May 10, 2024, the watt-hour rating must also appear on the outer case of every lithium-ion battery. For a broader look at how dangerous-goods classification affects freight pricing, see our overview of hazmat shipping and load rates.
Damaged, defective, and recalled batteries and EVs
Damaged, defective, and recalled (DDR) lithium batteries carry the strictest rules, and this is the category most relevant to finished-vehicle and fleet logistics. DDR batteries are forbidden for air transport and require heavy-duty packaging and specific handling for ground movement. A recalled EV battery pack, a fire-damaged unit, or a swollen cell cannot move like a normal shipment.
Vehicles add their own wrinkle. A battery-powered vehicle moving under its own installed pack ships under UN3171, and an electric vehicle in transit brings stranded-energy and reignition risks that the National Transportation Safety Board has documented for emergency responders (NTSB Safety Report SR2001, 2021). If your operation moves electrified units, our guide to hybrid and electric vehicle shipping covers the handling side, and this compliance layer sits underneath all of it. Managing recalled or defective packs is a distinct discipline, and RPM's team handles battery-bearing vehicles inside our broader finished vehicle logistics network.
Mode-by-mode requirements: air, ocean, and ground
The same battery faces different rules depending on how it travels, and confirming the mode before you package is what prevents a rebook. Air is the strictest, ocean sits in the middle, and U.S. ground transport is the most permissive on energy state. The table summarizes the practical differences.
ModeGoverning rulesKey constraints
Air
IATA Dangerous Goods Regulations / ICAO
30% state-of-charge cap on cargo aircraft; DDR batteries forbidden; strictest packaging and quantity limits
Ocean
IMDG Code (IMO)
Full Class 9 marking and documentation; stowage and segregation requirements
Highway and rail
49 CFR Parts 171 to 180 (PHMSA)
No state-of-charge cap; higher domestic watt-hour allowances; trained hazmat employees required
The takeaway for shippers who move batteries by more than one mode: package to the strictest mode in the chain. A battery prepared for air is compliant on the ground, but the reverse is not true. When a load may switch modes at a port or ramp, plan for the tightest rule it will encounter.
Packaging requirements
Packaging is where most preventable non-compliance starts, because the box does as much regulatory work as the paperwork. Fully regulated lithium batteries require UN-specification packaging tested to the Packing Group II performance level, which means the outer package has passed a drop test and is marked with the corresponding UN packaging code. Beyond the outer box, three requirements do the safety work:
- Short-circuit prevention: terminals must be protected and batteries packed to prevent contact with conductive material or each other, the single most important packaging function.
- Inner packaging and cushioning: cells and batteries must be secured against movement and protected from damage that could breach a cell.
- Drop-test integrity: the complete package must withstand a 1.2 meter drop without shifting contents or exposing terminals.
Excepted smaller batteries carry lighter packaging duties but still require terminal protection and a package that prevents short circuits. Getting the box wrong turns an otherwise compliant shipment into a refused one, regardless of how good the documentation looks.
Five mistakes that get lithium loads refused
Most refusals trace to a short list of avoidable errors. Check your process against these before you tender:
- Wrong UN number. Shipping batteries packed with equipment under UN3480 instead of UN3481, or confusing ion and metal, cascades into wrong marks and papers.
- Missing watt-hour rating. Since May 10, 2024, the Wh rating must appear on the battery case; an unmarked battery invites a hold.
- Over-complying on state of charge. Applying the 30% cap to a ground shipment is not a violation, but assuming it applies everywhere signals a shipper who has the rule wrong, and the reverse error, shipping air freight above 30%, gets the load pulled.
- Undocumented test summary. No available UN 38.3 test summary is grounds for refusal on its own.
- Improper package marks. A lithium battery mark under the 100 mm minimum, or a missing Cargo Aircraft Only label where required, stops the shipment at tender.
A compliance decision flowchart
Run every lithium battery shipment through the same five questions, in order, before you tender it:
- Is it damaged, defective, or recalled? If yes, it is forbidden by air and needs DDR ground handling. Stop and route accordingly.
- Ion or metal? This sets whether you measure watt-hours or grams of lithium.
- Alone or with equipment? This assigns the UN number (UN3480/UN3090 alone, UN3481/UN3091 with equipment).
- Over or under the threshold? Compare the rating to the small-cell and small-battery limits for your mode to decide excepted versus fully regulated.
- Which mode? Confirm air, ground, or ocean, then apply the marks, labels, papers, and any state-of-charge cap for that mode.
Answer those five and the packaging, marking, and paperwork follow directly.
Training, emergency response, and a repeatable process
Compliance is a process, not a one-time check, and two requirements make it durable. First, anyone who classifies, packages, marks, or offers lithium batteries is a hazmat employee and must be trained and certified under 49 CFR 172.704, with retraining at least every three years. An untrained shipper is a violation even when the box and paperwork are correct. Second, fully regulated shipments must carry emergency response information on the shipping papers, so a first responder knows what they are dealing with if a package is damaged.
That matters because a lithium fire behaves differently from an ordinary one. The National Fire Protection Association has documented that lithium-ion fires can reignite hours after they appear extinguished and demand far more water to cool than a conventional fire (NFPA). Emergency response information on the papers is what connects a damaged package to the right response.
The operators who never get a load refused build a standard operating procedure around the five-question flow above, keep a current test summary on file for every battery model, and treat training as a recurring calendar item rather than a form. For shippers moving batteries as part of finished-vehicle freight, that discipline folds into the broader finished vehicle logistics workflow rather than sitting beside it.
Frequently asked questions
What hazard class are lithium batteries for shipping?
Lithium batteries are Class 9 miscellaneous hazardous materials under 49 CFR, shipped under UN3480 or UN3090 when batteries travel alone and UN3481 or UN3091 when packed with or inside equipment.
What is the difference between UN3480 and UN3481?
UN3480 covers lithium-ion batteries shipped by themselves, while UN3481 covers lithium-ion batteries packed with or installed inside a piece of equipment.
Does the 30% state-of-charge rule apply to trucking?
No. The 30% state-of-charge limit applies to lithium-ion batteries shipped by cargo aircraft. U.S. highway and rail transport has no state-of-charge cap.
Do lithium batteries have to pass UN 38.3 testing?
Yes. Every lithium cell and battery must pass the eight design tests (T.1 through T.8) in Section 38.3 of the UN Manual of Tests and Criteria, and a UN 38.3 test summary must be available on request.
Can damaged or recalled lithium batteries be shipped?
Damaged, defective, and recalled lithium batteries are forbidden on aircraft and require special heavy-duty packaging and handling for ground transport.
What markings do fully regulated lithium battery shipments need?
They need the Class 9 lithium battery label, the UN number and proper shipping name, hazmat shipping papers with emergency-response information, and a watt-hour rating on the battery case.
What is UN3171 and when does it apply?
UN3171 is the entry for a battery-powered vehicle or equipment, and it applies when the battery is installed and powers the unit, such as an electric vehicle moving with its pack in place, rather than a loose battery shipped on its own.
How often do hazmat employees need training?
Anyone who classifies, packages, marks, or offers lithium batteries must be trained and certified under 49 CFR 172.704, with recurrent training at least once every three years.
Moving batteries, battery-powered equipment, or electrified vehicles across the country? Request a compliance review and we will pressure-test your classification, packaging, and paperwork before the load moves.
