Many Shippers Use the Wrong DOT Packing Section for Lithium Batteries

Most industrial lithium-ion packs ship under Section IA. The line that decides it is watt-hours: 100 Wh for a battery, 20 Wh for a cell. Almost nothing that goes into an AGV, an AMR, or a robot arm comes in under that line. Section II is for small cells and small batteries, and nothing else. Section IB exists only for small cells and small batteries that spill past the Section II package quantity limits. The section is a function of the watt-hour rating, how the battery is presented for transport, and how much of it sits in one package — not of how routine the shipment feels.

I had a 630 watt-hour pack on the bench, a tape gun in one hand, and a box on the floor that somebody had already built, closed, and marked. The third-party logistics review had gone through the SOP the week before and called it clean. The pack was going out as a service spare for a customer whose AMR had dropped one mid-shift.

The box was a good double-wall. The lithium battery mark sat square in the middle of the long side, 120 mm across, red hatched border, UN number printed in the corner, our 24-hour number underneath. Everything about it said Section II. That's exactly what it had been built for, and exactly what it wasn't.

What wasn't on that box was a UN specification marking. No 4G, no performance letter, no number, no country code. Nothing. And you're allowed to do that under Section II. You are not allowed to do it at 630 watt-hours.

I put the pack on the scale, got 5.9 kg, and did the arithmetic that decides everything downstream. Three of those would fill a package. Ten kilograms net is the Section II ceiling that matters for a cargo aircraft, so the count wasn't the problem. The pack was the problem. 630 Wh is more than six times the battery cutoff, and no quantity limit was going to rescue it.

So here's how I sort these now, in the order I actually do it.

The three sections, and the single number that sorts them

Under the packing instructions that PHMSA incorporates by reference for air transport, lithium ion cells and batteries shipped alone come in three sections.

Section IA covers cells over 20 Wh and batteries over 100 Wh. UN specification packaging, Class 9 lithium battery hazard label, shipping papers, a trained shipper, and no net quantity limit per package.

Section IB covers small cells and small batteries — 20 Wh and under, 100 Wh and under — that exceed the Section II net quantity limits. Same treatment as IA: UN specification packaging, Class 9 label, shipping papers.

Section II covers those same small cells and small batteries, inside the quantity limits. Strong outer packaging, no UN specification, the hatched lithium battery mark with a phone number, no Class 9 label, no shipping paper or Shipper's Declaration.

Lithium metal runs the identical three-section structure with the cutoff stated in grams instead of watt-hours — 1 gram of lithium per cell, 2 grams per battery.

Notice what the sections are not. They are not tiers of severity you get to choose from. They're defined categories with disjoint membership. A pack is in IA or it's in II. There's no judgment call in between, only a watt-hour number you either read correctly or don't. The sections have also been amended repeatedly over the years, which is why I work out of the current edition of whatever regulation the shipment actually moves under, not out of the training deck somebody keeps in a drawer.

That's the whole reason the wrong section gets used so often. This isn't a hard decision. It's an easy decision made with a stale number.

Where the number comes from, and where it goes stale

The rating you compare against the threshold is the rated capacity in watt-hours, printed on the pack label and stated on the cell datasheet. Not the usable capacity. Not the nameplate after the BMS reserves a top and bottom buffer.

I've watched a sourcing engineer describe a pack as "about 80 watt-hours" because that's what the robot consumes before the low-voltage cutoff. The label said 118 Wh. The label is the number. A reserve you never intend to use is still capacity, and whoever reads your shipping paper is going to read the label, not your duty cycle.

Two things push a program across the line without anyone deciding to cross it. Cell changes are the first. A supplier swaps in a higher-capacity cell to fix a runtime complaint, the pack goes from 96 Wh to 132 Wh, and the packaging SOP written eighteen months ago quietly becomes wrong. Firmware changes are the second, and they push in the other direction: someone raises the low-voltage cutoff to protect cycle life, the usable energy drops, and a person downstream decides the pack is now a "small battery." Usable energy has nothing to do with it. Only the rated watt-hours.

When Section II is genuinely available

Section II opens when two conditions hold at the same time, and both have to be checked. The cell is 20 Wh or less and the battery is 100 Wh or less, and the net quantity of batteries in the package is inside the limit for the mode. For standalone lithium ion moving by air, that net limit is 10 kg per package on cargo aircraft. Standalone lithium ion has been barred from passenger aircraft cargo for years, so the 2.5 kg passenger figure in older training decks is mostly a historical artifact by now.

For the people I work with, the practical fact is that Section II is a narrow door. In a fleet of AMR and AGV packs, the items that come in under 100 Wh are typically the small-format cells in sensors and handheld controllers — not traction packs. The moment you're looking at 24 V or 48 V with real capacity, you're in IA, and you have been the entire time.

Section IB is almost never the right answer for an industrial program either, because you can only get there with small cells and small batteries. If your pack is over 100 Wh, IB is not a softer landing than IA. It simply isn't open to you.

What changes the moment the pack is installed

This is the part that makes a section number on a spec sheet close to useless on its own.

The same 630 Wh pack that goes out as a spare, alone in a crate, is UN3480 and lives under Section IA. Put that pack into the AMR it was built for, secure it against movement, protect the terminals, and you're shipping UN3481 — lithium ion batteries contained in equipment. Different packing instruction, different section structure, and a much shorter list of obligations. In the contained-in-equipment case, the equipment is doing the work of the outer packaging, and on the ground there is frequently no UN specification packaging requirement at all.

Then there's the third configuration: batteries packed with equipment, which is a separate instruction from contained in equipment and carries its own limits and its own package quantity rules.

Three configurations, three rule sets, one part number.

So when somebody tells me their pack is "Section II," I ask which configuration. Not to be difficult. Because the answer changes what the box has to be, what the mark has to be, and what has to be on paper.

I keep a one-page matrix taped inside the shipping desk. Down the left side are the SKUs. Across the top are the configurations — installed, spare alone, spare packed with the unit, and the multi-pack case. In the cells: section, packaging part number, mark set, paper set. When a cell changes, the matrix gets re-run. It takes twenty minutes, and it's the only thing standing between a clean pickup and a package sitting on a dock.

Reading a UN specification box

If you're in Section IA or IB, the packaging has to be UN specification, and the evidence is stamped on the box. A string like 4G/Y30/S/25/USA/M1234 breaks down this way. 4G is a fiberboard box. Y is the performance level. 30 is the maximum gross mass in kilograms. S is for solids. 25 is the year of manufacture. USA is the country that authorized the design, and the last block is the packaging manufacturer's code.

Two pieces of that string get missed constantly.

The performance letter. X is Packing Group I, Y is Packing Group II, Z is Packing Group III. Lithium batteries sit in Packing Group II in the hazardous materials table, so a Y box is right, and an X box is also acceptable because a higher performance level covers a lower one. A Z box is not acceptable. I have found Z boxes in service because somebody bought on price and the sales sheet said "UN certified."

The gross mass number. That's the maximum the package can weigh — contents plus packaging — as it was tested. A 30 kg box carrying 34 kg of packs is out of compliance even though the box itself is exactly the right design. Weigh the finished package. Not the pallet average. The package.

Verifying the packaging, not the claim

The UN marking is the manufacturer's assertion, and it's backed by a test report. When a packaging supplier can't produce the test report for the specific model code stamped on the box, that's the end of the conversation for me. I want the report matched to the code, and I want the closure instructions — the tape type, the number of strips, the sequence, whatever the tested design calls for.

Closure is where a compliant box stops being compliant. A properly rated fiberboard box closed with three random passes of whatever was on the bench is not a closed UN specification package if the test report specifies something else. This is the finding that shows up in an audit and nobody has a defense for it, because the box looked perfect and the contents were right.

Two more things I check before a pack goes in. That each battery is protected against short circuit — terminals covered, no loose metal riding along in the package. And that the contents cannot shift. Movement is what abrades a terminal cover over a thousand miles of truck.

Overpacks and outer packaging

Industrial packs rarely go out as a bare box. They go on a pallet, or inside a crate, or stretch-wrapped with other units. The moment you put a compliant package inside another enclosure, you have an overpack, and overpacks have their own marking rules.

The overpack has to be marked "OVERPACK" and carry the UN number and the hazard label — unless the markings and labels on the packages inside are visible through or on the overpack, in which case you don't duplicate them. For a Section II package there's no Class 9 label to worry about, but the lithium battery mark still has to be visible, or replaced on the outside of the overpack.

The mistake I see most is treating the crate as the packaging. A heat-treated wood crate is not a UN specification packaging. It doesn't make an unmarked box compliant, and it doesn't upgrade a Section II package into a Section IA package. The UN specification box inside does that. The crate is just an overpack around it.

Paperwork follows the section

For Section IA and IB, you need a shipping paper reading UN3480, Lithium ion batteries, 9, PG II, with an emergency response telephone number, and for air a Shipper's Declaration signed by someone trained on the current edition. For Section II on the ground, no shipping paper is required, and for air no Shipper's Declaration — the mark does the work. Keep the classification worksheet and the packaging test reports anyway. That's what you produce when a carrier or an inspector asks why you called it what you called it.

And the person making the section call has to be hazmat-trained, with recurrent training, because classification is one of the functions the training rules cover. That isn't a paperwork formality. It's the reason a wrong section gets caught before the truck arrives rather than after.

One more seam worth naming. Air and ground don't use the same vocabulary. The IA/IB/II sections come from the packing instructions PHMSA incorporates by reference for air. Domestic ground shipments run under 49 CFR 173.185, which has its own exception for small cells and small batteries with a 30 kg gross weight limit per package — and no section names at all. Ocean has its own sections in the IMDG Code, which won't line up exactly either. A shipment that goes by truck to a port and then by vessel changes frameworks halfway, and the packaging has to satisfy the strictest one it will meet along the way.

The decision, in order

Read the rated watt-hours off the label. Confirm against the cell datasheet. Decide how the pack is presented — alone, packed with equipment, or contained in equipment. Pick the packing instruction from the presentation, then the section from the watt-hours and the net quantity per package. Choose packaging that matches the section and the gross mass. Verify the marking and the test report. Apply the right marks, the right labels, and the right paper. Then write it down, because the next person to touch that SKU won't have the number in their head, and the cell will change.

None of that is complicated. It's just that every step depends on a number that moves, and the sections never announce when you've left one behind.