Less stored energy
Shipping at a reduced SoC means less energy is available to feed a thermal event if a fault occurs in flight.
Guide
State of Charge (SoC) for Lithium Batteries by Air
When a lithium-ion battery shipment moves by air, the carrier may ask more than “is it UN38.3 tested?” It may also ask how much energy is stored in the cells right now — their state of charge. Here is what SoC means, why it matters in the air, and how to present it so your booking is not held up.
By the Cargo163 operations team · Updated 30 September 2026 · 7 min read
State of charge (SoC) is simply how full a battery is, expressed as a percentage of its usable capacity. A cell at 100% SoC is fully charged; a cell at 30% holds roughly a third of the energy it could hold. SoC is not the same as battery health or cycle life — it only describes the energy stored at a single moment.
The reason regulators care is straightforward: the more energy packed into a cell, the more energy is available to release if something goes wrong in flight.
The risk
Why SoC matters for air transport
A lithium cell stores chemical energy. Under damage, short circuit or defect, that energy can release as heat and trigger thermal runaway — a self-accelerating reaction that can spread to neighbouring cells.
Lower escalation risk
Cooler, less-charged cells are generally less likely to propagate a failure across a package or pallet.
Guidance in the DGR
For certain UN3480 shipments, current IATA guidance sets a state-of-charge limit (commonly around 30%).
Important: this limit is not universal and it is not fixed. It applies to specific battery configurations and can change with each IATA edition, so the applicable requirement must always be confirmed for the shipment in front of you.
Scope
Which shipments it usually applies to
The state-of-charge limit is most associated with loose lithium-ion cells and batteries shipped on their own, classified as UN3480 and transported as Class 9 dangerous goods. These are the standalone packs — replacement batteries, battery modules, cells for assembly — where the battery is the cargo.
Batteries that are packed with, or contained in, equipment (commonly UN3481) are handled under different provisions, and the SoC restriction does not apply in the same way. Because the rules hinge on classification and configuration, an accurate product description is what determines whether the limit is even relevant to your consignment.
When in doubt, tell us what is physically in the box — a bare battery, a battery in a device, or a battery shipped alongside a device — and we will confirm the right classification before quoting.
Quick orientation
- UN3480 loose cells/batteries — most likely to attract an SoC limit for air
- UN3481 in/packed with equipment — different provisions, SoC rarely the deciding factor
- Lithium metal (UN3090/3091) — separate rules again; SoC is a lithium-ion concept
Configuration drives the rule; never assume the limit applies to every battery.
Documents
How to present SoC to the carrier
Airlines and ground handlers want a statement they can rely on, not a guess. Treat state of charge as part of the dangerous-goods paperwork.
Measure before packing
Record SoC from the BMS or a reliable charge indicator at the point the shipment is prepared.
State it on the declaration
Include the SoC figure in the Shipper's Declaration for dangerous goods where the carrier requires it.
Support with proof
A factory test record or packing list note showing SoC makes the claim verifiable.
Keep it consistent
The SoC figure should agree with your other documents and the Wh rating on the label.
Delays
Common SoC issues that delay bookings
No figure provided
The declaration is silent on state of charge, so the carrier cannot accept a shipment it may be restricted to a limit for.
Shipped near full charge
Cells leave the factory or the customer at high SoC and need time to be discharged to an acceptable level.
Assumed it never applies
A UN3480 consignment is booked without checking whether the current IATA edition imposes a limit for that configuration.
Most of these are avoidable with one thing: confirming the applicable rule and the actual SoC before the cargo is presented, not after it reaches the warehouse.
Shipping lithium-ion batteries by air?
Tell us the classification and configuration — we confirm whether a state-of-charge limit applies and check your documents before recommending a compliant route.
Related reading: Battery Shipping from China · UN3480 vs UN3481 · Class 9 Lithium Battery Labels · How to Ship Lithium Batteries by Air · All guides
Note: State-of-charge requirements are set by IATA Dangerous Goods Regulations and related rules, which are updated periodically and can differ by configuration, transport mode and carrier. For certain UN3480 shipments the current guidance sets a SoC limit commonly around 30%, but this is not a fixed universal rule. This guide is general logistics information and does not replace the applicable dangerous-goods regulations. Cargo163 confirms the current requirement for each shipment before it is booked.