Yes. Lithium batteries are classified as hazardous materials under U.S. and international transportation rules, sitting in Class 9 (Miscellaneous Dangerous Goods).1International Air Transport Association (IATA). Lithium Battery Guidance Document That applies to rechargeable lithium-ion batteries in phones, laptops, power banks, and electric vehicles, and to non-rechargeable lithium metal batteries in watches, cameras, and medical devices. The hazmat label carries real consequences: it dictates how you can pack them, whether they fly in the cabin or the cargo hold, how you can mail them, and how you have to throw them away.
Why They Get the Hazmat Label
The concern is thermal runaway. A lithium battery that gets punctured, crushed, short-circuited, overcharged, or overheated can spike internally to temperatures of 700°C to 1,000°C, releasing toxic and flammable gases. In an enclosed space like a cargo hold, that risks explosion. Once one cell goes, the heat can cascade to neighboring cells, and reignition remains possible for hours after a fire appears to be out. Lithium metal is also highly reactive on its own: a cracked casing exposing the metal to air or moisture can ignite. Those properties are why regulators pulled lithium batteries into the dangerous goods framework in the first place.
How the Classification Works: UN Numbers
Under the UN system, each lithium battery type gets a four-digit identifier based on chemistry and how it’s packaged:2United Nations iLibrary. Recommendations on the Transport of Dangerous Goods: Model Regulations
- UN3480 — lithium-ion batteries shipped on their own
- UN3481 — lithium-ion batteries packed with equipment or installed inside equipment
- UN3090 — lithium metal batteries shipped on their own
- UN3091 — lithium metal batteries packed with or installed inside equipment
Standalone batteries face the strictest handling because a loose battery is more exposed than one nested in a device. Standalone lithium-ion batteries are banned from passenger aircraft entirely and can only move on cargo-only flights at no more than 30% state of charge.3Pipeline and Hazardous Materials Safety Administration (PHMSA). Frequently Asked Questions: Enhanced Safety Provisions for Lithium Batteries by Aircraft IFR
Flying With Lithium Batteries
This is where most people bump into the hazmat classification without realizing it. The rule for passengers: spare lithium batteries and portable power banks go in your carry-on, never in checked luggage.4Federal Aviation Administration. Airline Passengers and Batteries If a battery fails in the cabin, the crew can respond. A fire in the cargo hold may not be caught in time.
What you can bring depends on the watt-hour rating:
- 100 Wh or less: allowed in carry-on without airline approval. This covers phone batteries (roughly 10–15 Wh), standard laptop batteries (around 50–70 Wh), and typical power banks.
- 101 to 160 Wh: allowed in carry-on only with airline approval, and limited to two spares per passenger. Larger laptop batteries and professional camera batteries can fall here.5TSA. Lithium Batteries With More Than 100 Watt Hours
- Over 160 Wh: prohibited on passenger aircraft. Large e-bike batteries and some power tool batteries exceed this limit.
Devices with batteries installed, like your phone or laptop, can go in either carry-on or checked bags. The carry-on rule is about spare, uninstalled batteries. Tape over the terminals of spares or keep each one in its own case or original packaging so nothing shorts against a set of keys or a coin.
Mailing Batteries Through USPS
The Postal Service layers its own rules on top of DOT requirements. Standalone lithium batteries can only travel by ground within the United States. Air mail is generally off limits for loose batteries.6Postal Explorer. USPS Packaging Instruction 9D – Lithium Metal and Lithium-ion Cells and Batteries, Domestic
When batteries are installed in or packed with a device, USPS allows both surface and air mailing, provided each cell is 20 Wh or less and each battery 100 Wh or less for lithium-ion, or 1 gram of lithium per cell and 2 grams per battery for lithium metal. Each mailpiece is capped at eight cells or two batteries, and packages containing standalone batteries can’t exceed 5 pounds.
Used, damaged, or defective devices with lithium batteries inside must ship by surface only and be marked on the address side with “Restricted Electronic Device” and “Surface Transportation Only.”
Shipping Batteries Commercially
If you’re sending lithium batteries in commerce, the full hazmat apparatus applies. Ground transport by truck and rail is governed by the Department of Transportation’s Hazardous Materials Regulations at 49 CFR Parts 171–180.7eCFR. 49 CFR Part 171 – General Information, Regulations, and Definitions Air cargo follows the IATA Dangerous Goods Regulations, and sea shipments follow the IMDG Code.8PHMSA. Lithium Battery Guide for Shippers
The core requirements come in three layers. Packaging: each cell or battery sits in a non-metallic inner package that prevents contact with other batteries or conductive materials, with cushioning around it and a strong rigid outer box or drum tested to DOT performance standards.9eCFR. 49 CFR 173.185 – Lithium Cells and Batteries Marking and paperwork: the Class 9 hazard label, the correct UN number, the proper shipping name, and in many cases a lithium battery handling mark with red diagonal hatching, plus a Shipper’s Declaration for Dangerous Goods describing the contents and hazard class.10eCFR. 49 CFR 172.446 – CLASS 9 Label Emergency contact: shipping papers must carry a 24-hour phone number staffed by someone who knows the material and can give emergency response guidance. An answering machine doesn’t count.11eCFR. 49 CFR 172.604 – Emergency Response Telephone Number
Anyone who prepares, packages, labels, or handles these shipments qualifies as a hazmat employee and must be trained before working unsupervised, with refresher training at least every three years.12eCFR. 49 CFR 172.704 – Training Requirements Small e-commerce sellers often assume the training rule doesn’t apply to them. It does, even when the batteries are small enough to qualify for reduced packaging.
Exceptions for Smaller Batteries
Not every shipment triggers the full burden. Smaller consumer batteries qualify for simplified rules when they meet these thresholds:8PHMSA. Lithium Battery Guide for Shippers
- Lithium-ion: cells rated at 20 Wh or less, batteries at 100 Wh or less
- Lithium metal: cells with 1 gram of lithium or less, batteries with 2 grams or less
Batteries at or under those numbers, packed in limited quantities, can ship with reduced packaging, marking, and documentation. Batteries already installed in a device get the most relief because the equipment provides physical protection. Basic safeguards like short-circuit prevention and sturdy outer packaging still apply.
Damaged, Defective, or Recalled Batteries
Batteries that are physically damaged, flagged defective by the manufacturer, or subject to recall can’t fly at all. They move only by highway, rail, or vessel.9eCFR. 49 CFR 173.185 – Lithium Cells and Batteries Packaging is tighter than for new batteries: each battery goes in a non-metallic inner package surrounded by cushioning that is non-combustible, electrically non-conductive, and absorbent, inside an outer container built to the most demanding performance tier (Packing Group I). The outside must be marked “Damaged/defective lithium ion battery” or “Damaged/defective lithium metal battery” in characters at least 12 mm high.
Penalties for Getting It Wrong
Federal civil penalties reach up to $102,348 per violation, and up to $238,809 when a violation causes death, serious injury, or major property damage.13eCFR. 49 CFR 107.329 – Maximum Penalties The current figures were set in late 2024 and adjust for inflation. Willful or reckless violations can bring criminal charges carrying up to five years in prison, or up to ten years when the violation causes a release resulting in death or bodily injury.14eCFR. 49 CFR Part 107 Subpart D – Enforcement
These aren’t hypothetical. The FAA proposed a $170,000 penalty against a Virginia company for shipping undeclared lithium-ion phone batteries by air through FedEx without proper classification, packaging, marking, or labeling.15Federal Aviation Administration. FAA Proposes $170,000 Civil Penalty Against Mobile Sentrix for Alleged HazMat Violations The most common violation pattern is exactly that: a shipper who doesn’t know the batteries need hazmat treatment and sends them as ordinary goods.
Disposal and Recycling
The classification follows the battery to end-of-life. EPA considers most discarded lithium batteries hazardous waste because of their ignitability and reactivity, and recommends managing used lithium-ion and lithium metal batteries under the federal universal waste rules at 40 CFR Part 273.16Environmental Protection Agency (EPA). Lithium Battery Recycling Regulatory Status and Frequently Asked Questions Universal waste handling is lighter than full hazardous waste handling — no manifest required to ship — but the batteries still have to end up at a permitted disposal facility or recycler. Handlers accumulating more than 5,000 kilograms of universal waste on-site at one time face stricter obligations. Regular trash isn’t an option: a crushed battery in a garbage truck or landfill compactor can ignite.