Lithium batteries are the freight most forwarders quietly decline. The rules are detailed, they change every year, and getting them wrong means a rejected booking at best. But they’re not mysterious — how a lithium battery ships comes down to four questions.
1. Ion or metal?
- Lithium-ion (rechargeable — the common case): phones, tools, e-bikes, inverters, most electronics.
- Lithium-metal (usually non-rechargeable): coin cells, certain industrial and medical batteries.
They get different UN numbers and, for air, different limits. Metal is treated more strictly.
2. Alone, in equipment, or packed with it?
This is the distinction people miss most. The same battery ships under a different UN number depending on how it’s packed:
| Shipped alone | In or packed with equipment | |
|---|---|---|
| Lithium-ion | UN3480 | UN3481 |
| Lithium-metal | UN3090 | UN3091 |
A battery installed in a machine and a loose battery in the same box are two different shipments on paper. (There’s also UN3536 for lithium batteries installed in a cargo transport unit.)
3. How big — the watt-hour rating
The watt-hour (Wh) rating for batteries, or grams of lithium for metal cells, decides how heavily the shipment is regulated. Small cells and batteries below the thresholds get some relief; above them, the full requirements apply — stronger packaging, more marking, and a dangerous-goods declaration. The rating comes off the safety data sheet and the battery itself; don’t estimate it.
4. Sea or air — and the 30% rule
This is where a shipment that’s easy by ocean becomes hard by air.
- By sea (IMDG Code): lithium batteries ship as Class 9 with defined packing and marking. Workable for most volumes.
- By air (IATA DGR): much tighter. The one rule everyone must know — lithium-ion cells and batteries shipped on their own (UN3480) must be at a state of charge of 30% or less. Carriers check, and over-charged batteries are rejected at the counter.
So the honest answer to “can this fly?” is often “yes, if it’s at 30% and packed to the air standard — otherwise it goes by sea.” Deciding mode early saves a scramble later.
The mistakes we see most
- Trade name instead of proper shipping name on the declaration.
- Wrong UN number because the packing configuration (alone vs. in equipment) was misread.
- An out-of-date SDS that no longer matches the current rules.
- Booking air without checking state of charge, then getting stopped at acceptance.
- Assuming “it’s just a small battery” exempts it — the small-battery relief has real limits and has been tightened.
Before you book
Have the SDS, the watt-hour rating, the quantity, and the packing configuration ready, and decide sea vs. air up front. This is a lane we quote every week, not once in a while — send us the details and we’ll confirm exactly how your batteries have to move, and whether they can fly.