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Over-temperature protection

Verifies the battery system's overheat protection terminates or limits operation before thermal damage occurs — exercises the BMS thermal-cutoff logic under combined ambient and charge/discharge thermal load.
Clause (method) 8.2.11
Clause (pass criteria) 5.2.11
Object system
Status vs. 2020 revised
Observation period 1 h at test environment temperature

Pass criteria

After the over-temperature protection test, the battery system shall show no leakage, no housing crack, no fire, and no explosion. The insulation resistance after testing shall not be less than 100 Ω/V (DC), or 500 Ω/V if an AC circuit is present.

Source: GB 38031-2025, clause 5.2.11 (PDF p. 12).

Pre-conditions

  • Object: The test object is a battery system (not a bare pack). (8.2.11.1)
  • Pre-treatment: Standard, per clause 7.2.
  • SOC: Highest working SOC per clause 6.1.10.
  • Protection devices: All protection devices that affect the function of the test object and are related to the test results, except for the cooling system, shall be in normal operating condition. (8.2.11.2)
  • Insulation baseline: Measure before the test per Appendix B (clause 6.1.5).

Test parameters

Parameter Value Source
Initial chamber temperature 20 °C ± 10 °C (or higher per manufacturer) 8.2.11.4
Chamber target (with overheat protection) Manufacturer's overheat-protection operating-temperature threshold 8.2.11.4 a)
Chamber target (without overheat protection) Manufacturer's maximum operating temperature 8.2.11.4 b)
Forcing current Continuous charge/discharge to drive cell T up as fast as possible within mfr normal operating range 8.2.11.3
Cooling system Disabled (other protections active) 8.2.11.2
Termination conditions Auto cutoff / manufacturer signal / T stable (ΔT < 4 °C over 2 h) 8.2.11.5
Post-test observation 1 h at test environment temperature 8.2.11.6

Procedure

  1. Confirm pre-treatment per 7.2 and measure baseline insulation per Appendix B. (6.1.5)
  2. Adjust SOC to highest working value. (6.1.10)
  3. Confirm all protection devices except the cooling system are in normal operating condition. (8.2.11.2)
  4. Place the test object in a temperature chamber and connect external charging/discharging equipment.
  5. Begin continuous charge and discharge with current sized to drive cell temperature up as quickly as possible within the manufacturer's normal operating range. (8.2.11.3)
  6. Gradually ramp the chamber temperature from 20 °C ± 10 °C (or higher per manufacturer) to:
  7. the manufacturer's overheat-protection operating-temperature threshold (if equipped), or
  8. the manufacturer's maximum operating temperature (if no overheat protection). (8.2.11.4)
  9. Maintain that temperature (or higher) until any termination condition is met. (8.2.11.4, 8.2.11.5)
  10. Terminate when any of the following occurs: a. The test object automatically terminates or limits charging/discharging. b. The test object sends a signal to terminate or limit charging/discharging. c. The test object's temperature stabilizes (ΔT < 4 °C over 2 h). (8.2.11.5)
  11. Observe the test object at the test environment temperature for 1 hour. (8.2.11.6)
  12. Re-measure insulation per Appendix B; inspect for leakage, housing cracks; confirm no fire/explosion.

After-test observation

Observe the test object for 1 hour at the test environment temperature (22 °C ± 5 °C) after the termination condition is met. (8.2.11.6)

What changed from GB 38031-2020

  • Listed in the preface change list as both requirements (5.2.11) and method (8.2.11) revised.

Migration impact: Already-type-approved vehicle models must comply from 2027-08-01. New type approvals from 2026-07-01. See Re-certification timeline.

Engineering notes (non-normative)

The notes below are practical interpretation, not part of the standard.

Engineering note (non-normative): The test exercises the BMS thermal-protection path, not cell thermal stability. With the cooling system disabled and current driving heat in, the question is whether the BMS de-rates or cuts off before damage. A pack that finishes the test on the temperature-stable termination (option c) — rather than on auto-cutoff — has demonstrated that its thermal management absorbs the worst case without needing protection to fire, which is a stronger result.

Engineering note (non-normative): "Continuous charging and discharging" is intentionally vague — the manufacturer chooses the rate to maximize heating within the normal operating envelope. Document the chosen current profile; type-approval reviewers will scrutinize whether the rate is genuinely aggressive or a soft case that lets the BMS off easy.