Tests that got stricter¶
Per the preface, the following pack/system requirements clauses (5.2.x) were revised. The headline is 5.2.7 thermal stability: pack-level "no fire, no explosion" plus a 5-minute warning signal. The other revisions tighten or restate pass criteria around leakage, housing crack, fire/explosion, and the ≥ 100 / ≥ 500 Ω/V insulation thresholds.
Headline change — 5.2.7 thermal stability¶
Safety requirements and test methods for thermal stability of battery packs or systems have been revised (see 5.2.7, 8.2.7, and Appendix C, 2020 Edition 5.2.7, 8.2.7, and Appendix C).
The 2025 text:
5.2.7 After undergoing the thermal stability test as per 8.2.7 (excluding nickel-hydride battery packs or systems), the following requirements apply: a) The battery pack or system, after undergoing the external fire test as per 8.2.7.1, should not explode. b) The battery pack or system or the entire vehicle, after undergoing the thermal propagation analysis and verification as per 8.2.7.2, should: 1) No fire, no explosion; 2) Provide a thermal event warning signal, and the warning signal should be sent no later than 5 minutes after thermal runaway of the battery cell is triggered; 3) For battery pack or system-level testing, provide technical documentation indicating that smoke does not pose a danger to the passenger compartment within 5 minutes before and after the thermal event warning signal is issued; for vehicle-level testing, smoke should not enter the passenger compartment within 5 minutes before and after the thermal event warning signal is issued.
Three step-changes from the 2020 text:
- No fire, no explosion at the pack/system level after thermal propagation. The 2020 edition required only a 5-minute warning before fire/explosion reached the passenger compartment.
- The 5-minute warning clock now starts at thermal-runaway trigger, not at thermal runaway occurrence — narrower window for detection logic.
- Smoke is now an explicit pass criterion: documented not to endanger the cabin within ± 5 min of the warning, or for vehicle-level tests, must not enter the cabin in that window.
See thermal propagation for the full Appendix C procedure.
Engineering note (non-normative): the "no fire, no explosion" pack-level criterion is the engineering definition of "thermal propagation prevention". OEMs that previously relied on detect-and-warn architectures must now suppress propagation outright — through cell chemistry choice, inter-cell barriers, fire-resistant pack venting, or a combination. This is the change with the largest BOM impact in the 2025 edition.
Other 5.2.x revisions¶
Listed verbatim from the preface:
| Clause | Test | Preface text |
|---|---|---|
| 5.2.1 | Vibration | "Safety requirements and test methods … have been revised" |
| 5.2.2 | Mechanical shock | "Safety requirements … have been revised" |
| 5.2.3 | Simulated collision | "Safety requirements … have been revised" |
| 5.2.4 | Compression | "Safety requirements and test methods … have been revised" |
| 5.2.5 | Damp heat cycling | "Safety requirements … have been revised" |
| 5.2.6 | Immersion | "Safety requirements … have been revised" |
| 5.2.7 | Thermal stability | see above |
| 5.2.8 | Temperature shock | "Safety requirements and test methods … have been revised" |
| 5.2.9 | Salt fog | "Safety requirements and test methods … have been revised" |
| 5.2.10 | High altitude | "Safety requirements and test methods … have been revised" |
| 5.2.11 | Over-temperature protection | "Safety requirements and test methods … have been revised" |
| 5.2.12 | Over-current protection | "Safety requirements and test methods … have been revised" |
| 5.2.13 | External short-circuit protection | "Safety requirements … have been revised" |
| 5.2.14 | Overcharge protection | "Safety requirements and test methods … have been revised" |
| 5.2.15 | Over-discharge protection | "Safety requirements … have been revised" |
Engineering note (non-normative): every pack/system test in the 5.2 block had its requirements re-stated in 2025. Most of the rewording aligns the criterion language to a single template ("no leakage, housing cracks, fire, or explosion; insulation ≥ 100 Ω/V; ≥ 500 Ω/V if AC"). The only test where the universal criterion is relaxed in the new edition is 5.2.4 compression, which keeps "no fire or explosion" plus the insulation threshold but drops the leakage and housing-crack requirements.
Cross-reference¶
- Tests with methodology changes — companion list for 8.x changes.
- Quick diff — the full preface change list.
Source¶
Preface and clause 5.2.7 (PDF pages 5–6, 12).