Quick answer: The 30% state-of-charge rule requires lithium-ion batteries shipped by air to carry no more than 30% of rated capacity. It applies to air transport only, under US and IATA rules, not to ground or rail. Lower charge reduces stored energy, cutting thermal-runaway severity and cell-to-cell fire propagation.
Battery state of charge, or SoC, is how much energy a lithium battery holds relative to its full capacity, and for shipping it is a compliance decision, not just a spec on a datasheet. The 30% SoC rule is the one most shippers know exists and most shippers state wrong, because it does not apply to every mode. Getting it right saves you from two opposite mistakes: over-restricting a ground shipment that has no limit, and under-preparing an air shipment that gets pulled. This guide covers where the rule applies, why 30% specifically, and how SoC quietly drives your mode and packaging choices.
Which modes the 30% rule applies to
The 30% SoC limit is an air-transport requirement, and understanding that scope is the whole game. Under the US Hazardous Materials Regulations, lithium-ion cells and batteries offered for transport by cargo aircraft must be at no more than 30% of rated capacity, through special provision A100 (49 CFR 173.185, PHMSA). Standalone lithium-ion batteries shipped by themselves are also barred from passenger aircraft entirely.
US highway and rail transport impose no state-of-charge limit. If you move batteries by truck or train, the 30% figure does not restrict you at all. That single distinction is where most shippers go wrong, applying an air rule to a ground load or, worse, assuming a fully charged battery legal to truck is also fine to fly. It is not. The mode you book determines whether the rule touches you.
Why 30% specifically
The 30% threshold exists because state of charge directly governs how dangerous a battery is if it fails. In a thermal-runaway event, the energy a cell releases scales with how charged it is, and so does whether that failure spreads to neighboring cells. Testing at the FAA's William J. Hughes Technical Center makes the relationship concrete: at 30% SoC, failing cells showed very little smoke and minimal damage with no visible flame, while at 70% SoC cells reached 400 to 700 degrees Celsius and propagated thermal runaway to adjacent cells, and at 100% the reaction was most violent (FAA Technical Center, 2022).
That is why the limit protects an aircraft hold specifically. A cargo compartment is confined, single-space, and impossible to reach in flight, so the rule attacks the hazard at its source by keeping stored energy low enough that one failing cell does not cascade into a fire. The vented gases from a runaway cell are themselves ignitable, which compounds the risk at higher charge. Lowering SoC is a source mitigation; it reduces the size of the problem before packaging ever has to contain it. For how that fits the broader classification picture, see our overview of hazmat shipping and load rates.
What changed on January 1, 2026
The 2026 update tightened the SoC rules for air, but not in the way most summaries claim. The 30% cap for standalone lithium-ion batteries (UN3480) by cargo aircraft is not new; it has been mandatory since the March 2019 PHMSA rule. What changed on January 1, 2026, under the IATA Dangerous Goods Regulations 67th Edition, is that the 30% limit became mandatory rather than recommended for additional categories:
- UN3481: lithium-ion batteries packed with equipment, rated above 2.7 Wh.
- UN3556: lithium-ion powered vehicles, rated above 100 Wh.
- Sodium-ion batteries brought into the same state-of-charge regime for air.
The practical takeaway is precision: do not lump every lithium shipment into a single "new 2026 rule." Standalone batteries were already covered, and the change specifically extends the mandate to batteries packed with equipment and to battery-powered vehicles above the stated thresholds (IATA, 2026). Because the exact thresholds and UN-number scope sit in the current DGR edition, verify against the published 67th Edition before you certify a borderline air shipment.
The 25% indicated-capacity alternative
There is a practical alternative to calculating 30% of rated capacity that many shippers do not know they can use. IATA accepts demonstrating compliance through a battery's indicated capacity of 25% or less, the reading on the device's own fuel gauge, as an equivalent safety mitigation. It is easier to verify at the dock than computing 30% of rated design capacity, because you read it off the battery rather than deriving it. IATA notes the 25% indicated figure is not numerically identical to 30% rated SoC but delivers an equivalent mitigation. For a compliance team preparing air freight at speed, it is often the more workable check.
How SoC changes packaging and mode choice
State of charge is not just a number to hit; it is a lever that shapes the rest of your shipment. Because lower SoC reduces the hazard the packaging has to contain, air rules pair the SoC limit with specific packing instructions and cargo-aircraft-only marking, stacking a source mitigation on top of a containment one. Reduce the charge and you reduce the severity the box must survive.
It also reshapes routing. A fully charged battery pack that cannot meet the 30% air limit may move freely by ground or rail, where no SoC ceiling applies. That makes state of charge a genuine mode-selection decision: if discharging to 30% is impractical for a given load, ground transport may be the compliant path rather than a delay. For finished vehicles and EVs carrying installed packs, the same logic runs underneath our hybrid and electric vehicle shipping guide, and damaged units follow the stricter rules in our guide to shipping damaged and defective lithium batteries.
The passenger-aircraft prohibition
Alongside the 30% cap sits a stricter rule for standalone batteries: lithium-ion batteries shipped by themselves (UN3480) are banned from passenger aircraft entirely, not merely limited in charge. This is a categorical prohibition, and it reflects the same logic as the SoC limit taken to its conclusion. A passenger aircraft cannot tolerate the risk of a battery fire in a cargo hold full of passenger baggage with people above it, so standalone lithium-ion batteries are confined to cargo aircraft, where they must also meet the 30% limit. Batteries packed with or contained in equipment are treated differently, because the equipment provides additional protection and a lower quantity of loose cells. The takeaway for shippers is that "can it fly" has two layers: whether the battery is allowed on the aircraft type at all, and, if so, at what state of charge.
How state of charge and packaging work together
State of charge and packaging are two mitigations that stack, and understanding how they combine explains why air rules pair them. Reducing charge is a source mitigation: it shrinks the amount of energy available to release if a cell fails. Packaging is a containment mitigation: it limits what a failure can do to its surroundings. Air regulations require both because neither alone is sufficient for the confined, unreachable environment of an aircraft hold. That is why the SoC limit comes bundled with specific packing instructions, cargo-aircraft-only marking, and quantity limits. For a shipper, this means hitting 30% does not substitute for correct packaging, and correct packaging does not substitute for the charge limit. Both apply, and both are checked. Our overview of hazmat shipping and load rates puts this in the wider dangerous-goods context.
Common state-of-charge mistakes
A handful of SoC errors account for most compliance problems, and all of them trace back to misreading the rule's scope:
- Applying the air limit to a ground load. Discharging batteries to 30% for a truck shipment is unnecessary and signals a shipper who has the rule's scope wrong.
- Shipping air freight above 30%. The opposite error, and the one that gets loads pulled at the airport.
- Assuming all UN numbers changed in 2026. Standalone battery limits are long-standing; only specific categories became mandatory on January 1, 2026.
- Calculating rated SoC when indicated capacity would do. The 25% indicated-capacity check is often faster and less error-prone at the dock.
- Ignoring the mode-choice option. When discharge is impractical, ground or rail may be the compliant route rather than a delay.
A shipper's state-of-charge decision guide
Work through these questions before you prepare a lithium battery shipment:
- What mode is this moving by? Air triggers the SoC limit; US ground and rail do not.
- If by air, what is the UN number and rating? Confirm whether the mandatory 30% cap applies to your battery under the current DGR edition.
- Can you verify by indicated capacity? A 25% indicated reading is often the faster equivalent check than calculating 30% of rated capacity.
- Is discharging practical? If not, consider whether ground or rail is the better compliant route for this load.
- Does the packaging and marking match? Pair the SoC state with the correct packing instruction and cargo-aircraft-only marking for air.
Where ocean and multimodal shipments fit
Most shippers think about state of charge in terms of air versus ground, but ocean and multimodal moves deserve a note. Ocean transport under the IMDG Code carries its own dangerous-goods requirements for lithium batteries, and a load that starts on the water may still touch air or ground on either end. The practical rule for any multimodal shipment is to prepare to the strictest mode the load will encounter. If any leg touches air, the air state-of-charge limit and packaging effectively govern the whole journey, because you cannot recharge a battery mid-route to suit a later leg. Mapping the full modal path before you set the charge state and packaging prevents a battery that was compliant for the first leg from being refused at a later one. When a route is uncertain or may switch modes at a port or ramp, planning to the tightest rule keeps the freight moving rather than stranded at a transfer point. Confirming the full itinerary with your carrier before the first leg is the simplest safeguard against a battery that clears one mode and fails the next.
Frequently asked questions
Does the 30% state-of-charge rule apply to trucking or rail?
No. US ground transport under 49 CFR 173.185 and rail set no state-of-charge limit; the 30% rule is an air-transport requirement.
What is the 30% SoC rule for lithium batteries?
Lithium-ion batteries shipped by air must be charged to no more than 30% of rated capacity, to reduce fire severity in the event of thermal runaway.
What changed for lithium batteries on January 1, 2026?
The IATA DGR 67th Edition made the 30% SoC limit mandatory, rather than recommended, for batteries packed with equipment (UN3481 above 2.7 Wh) and battery-powered vehicles (UN3556 above 100 Wh).
Was the 30% rule for standalone lithium-ion batteries new in 2026?
No. It has been mandatory on cargo aircraft since the March 2019 PHMSA rule, and standalone lithium-ion batteries have been barred from passenger aircraft since then.
Can I use indicated capacity instead of state of charge?
Yes. IATA accepts an indicated battery capacity of 25% or less as an equivalent, easier-to-verify alternative to the 30% rated SoC.
Why does lower state of charge make lithium batteries safer to ship?
A battery at 30% stores far less energy, so a failing cell releases less heat and flammable gas and is far less likely to ignite neighboring cells.
Are standalone lithium-ion batteries allowed on passenger planes?
No. Standalone lithium-ion batteries (UN3480) are prohibited from passenger aircraft entirely and may only travel on cargo aircraft, where they must also meet the 30% state-of-charge limit.
Does hitting 30% state of charge replace proper packaging for air shipments?
No. State of charge and packaging are separate mitigations that both apply, so an air shipment must meet the charge limit and use the correct packaging and marking.
Not sure whether your battery load needs to hit 30% or can ship fully charged by ground? Request a compliance review and we will confirm the mode, SoC, and packaging before it moves.
