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Leakage and housing crack

"No leakage" and "no housing crack" appear together in almost every pack/system pass criterion (5.2.x). Like fire and explosion, they are judged visually from the outside. Their definitions are short.

Definition — housing crack (3.13)

A mechanical damage to the battery cell, module, battery pack, or system housing caused by internal or external factors, resulting in the exposure or spillage of internal substances.

Two elements have to be present together: mechanical damage to the housing, and that damage causes exposure or spillage of internal substances. A scratch, dent, or surface deformation that does not expose internals is not a "housing crack" in the standard's sense.

Source: GB 38031-2025 clause 3.13 (PDF page 9).

Definition — leakage (3.14)

The phenomenon where visible substances leak from the battery cell, module, battery pack, or system to the outside of the test object.

Note: Visible substances are judged visually without dismantling the test object.

Two load-bearing details:

  1. Visible — invisible vapor or gas evolution does not, by itself, constitute leakage under this definition; the leaked substance has to be visible to the observer.
  2. Without dismantling — judgment is based on what can be seen on the outside of the assembled test object. The standard does not ask the lab to open the housing to look for internal pooling.

Source: GB 38031-2025 clause 3.14 (PDF page 9).

Engineering note (non-normative): "Leakage" in 3.14 was revised from the 2020 edition (where it was clause 3.13). The 2020 wording predated this explicit "visible / no dismantling" framing. For test reports being read by both Chinese and German type-approval staff, "Leckage (sichtbar, ohne Demontage beurteilt)" — visible leakage, judged without dismantling — captures the operational test.

Tests that require "no leakage, no housing cracks"

The standard pack/system criterion (5.2.x) almost always reads:

A battery pack or system, after undergoing the [test name] test as per 8.2.x, should show no leakage, housing cracks, fire, or explosion. The insulation resistance after testing should not be less than 100 Ω/V. If there is an AC circuit, the insulation resistance should not be less than 500 Ω/V.

This applies to:

Clause Test
5.2.1 Vibration (8.2.1)
5.2.2 Mechanical shock (8.2.2)
5.2.3 Simulated collision (8.2.3)
5.2.5 Damp heat cycling (8.2.5) — insulation measured within 30 min after test
5.2.6 b) Immersion Method 2 (IPX7)
5.2.8 Temperature shock (8.2.8)
5.2.9 Salt fog (8.2.9)
5.2.10 High altitude (8.2.10)
5.2.11 Over-temperature protection (8.2.11)
5.2.12 Over-current protection (8.2.12)
5.2.13 External short-circuit protection (8.2.13)
5.2.14 Overcharge protection (8.2.14)
5.2.15 Over-discharge protection (8.2.15)
5.2.16 Bottom impact (8.2.16)

Source: GB 38031-2025 clauses 5.2.1–5.2.3, 5.2.5, 5.2.6, 5.2.8–5.2.16 (PDF page 12).

Tests that do NOT require "no leakage, no housing cracks"

Clause Test Pass criterion
5.1.1–5.1.7 All cell-level tests (8.1.2 to 8.1.8) No fire, no explosion only — leakage and housing-crack absence is not required for cells.
5.2.4 Compression, pack/system (8.2.4) "Should show no fire or explosion. Insulation resistance ≥ 100 Ω/V…" — the only pack/system test where leakage and housing cracks are explicitly allowed. The compression plate is expected to deform the housing.
5.2.6 a) Immersion Method 1 (3.5 % NaCl, 2 h submerged) "There should be no fire or explosion." Method 1 does not list leakage/housing-crack absence (nor insulation). Method 2 (IPX7) does.
5.2.7 a) External fire (8.2.7.1) "Should not explode." Fire is allowed (the test is a fire test); leakage and housing-crack damage are expected and not failure criteria.
5.2.7 b) Thermal propagation (8.2.7.2) No fire, no explosion + 5-min warning + smoke-control. Leakage and housing cracks are not in the criterion.

Source: GB 38031-2025 clauses 5.1.1–5.1.7, 5.2.4, 5.2.6, 5.2.7 (PDF pages 11–12).

Engineering note (non-normative): The 5.2.4 carve-out for compression matters for type-approval review. A pack that fails the 8.2.4 compression test because its housing cracked is a misread of the criterion — only fire, explosion, or insulation drop below threshold can fail 8.2.4. A pack that fails because of fire, however, is unambiguous.

Cross-references