UN38.3 T.4 & T.5: Crush and Impact Tests

UN38.3 is the transport-safety test series every lithium cell and battery pack must pass before it can fly. Two of its eight tests — T.4 crush and T.5 impact — are the ones most often failed on the first attempt, and both are decided by set-up rather than by the machine alone.

T.4 crush

A cell is crushed between two flat plates at 13 kN with a displacement rate not exceeding 0.1 mm/s. The pass criterion is no fire and no explosion. The two practical traps: the plates must cover the whole cell so the load is not concentrated on one edge, and the force has to be held rather than released at the moment the target is reached.

T.5 impact

A 15.8 mm diameter bar is placed across the cell and a 9.1 kg mass is dropped from 61 cm onto it. The bar position matters — it must sit across the centre of the cell and perpendicular to its long axis, otherwise the sample is tested in bending rather than in compression.

Set-up checklist

Confirm the room temperature is inside the specified window, photograph the sample orientation before the run, keep the force-displacement curve for the report, and leave the sample under observation for the full post-test period. Test reports are challenged on documentation far more often than on the machine.

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