Why a cell counts as dangerous goods

A lithium cell holds a flammable electrolyte and a large amount of energy in a small volume. On external short circuit, crushing or internal defect, it can enter thermal runaway: a self-sustaining reaction that no ordinary extinguisher stops easily.

Air transport learned this the hard way, and international regulation followed. Cells are classified as class 9, under UN numbers UN3480 (cells alone) and UN3481 (cells in or packed with equipment). The classification applies whatever the state of charge, and whether the cell is new or second-life.

UN 38.3: the test series that governs everything

UN 38.3 is not a label but a test series, set out in the UN Manual of Tests and Criteria. A cell type must pass it before it can be transported lawfully. Eight tests, reproducing the stresses of transport:

  • T1 to T3: simulated altitude, thermal cycling, vibration.
  • T4: mechanical shock.
  • T5: external short circuit.
  • T6: impact or crush.
  • T7: overcharge.
  • T8: forced discharge.

The tests apply to a cell type, not to every unit. The test report — commonly called the “UN 38.3 report” — must be available on request along the chain.

ADR: the European road side

UN 38.3 qualifies the product; ADR governs its carriage by road in Europe. It sets packaging, marking, documentation and training requirements.

In practice three requirements dominate for cells:

  • Short-circuit protection: insulated terminals, cells immobilised, no possible contact between them or with conductive parts.
  • Approved packaging, able to absorb shocks and prevent contents from shifting.
  • Marking and documentation: class 9 lithium battery label, UN number, and a compliant transport document.

ADR allows lighter provisions below certain quantity thresholds, but they never waive short-circuit protection or marking.

The special case of second-life cells

A reused cell escapes none of these rules — and one point deserves to be stated plainly: a damaged or defective cell falls under far stricter provisions, and air transport is prohibited for it.

That is one reason we resell no cell below 70% SOH and systematically discard any punctured, swollen or corroded cell. Beyond product quality, it is a condition for the batch to be shippable at all. Our article on grades and SOH details that sorting.

What this changes for your order

In practice, three consequences you will see when ordering:

  • Carriage costs more than an ordinary parcel, and cannot be built into the cell price by default: it depends on weight, destination and transport mode.
  • Lead times are slightly longer, as packaging and paperwork cannot be improvised.
  • Some destinations are restricted, particularly by air.

This is why shipping is calculated at checkout rather than quoted loosely. For large volumes or an unusual destination, write to us: the best route depends on the case. Our cells and BMS are listed in the Pro Shop.

One caution

This article outlines the regulatory framework in broad terms; it replaces neither ADR itself nor your carrier's own rules, which may be stricter. If you ship cells yourself, have your procedure validated by a dangerous goods safety adviser.