Skip to content

Over-current protection

Verifies the battery system's over-current protection cuts off or limits charging when an external DC supply faults to a higher current than the system is rated for.
Clause (method) 8.2.12
Clause (pass criteria) 5.2.12
Object system
Status vs. 2020 revised
Observation period 1 h at test environment temperature

Pass criteria

After the over-current 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 5.2.12 (PDF p. 12).

Pre-conditions

  • Object: The test object is a battery system powered by an external DC power supply. (8.2.12.1)
  • Ambient temperature: 20 °C ± 10 °C. (8.2.12.2 a)
  • SOC: Adjust to the middle of the manufacturer-recommended normal operating range (precise adjustment not required as long as the system can operate normally). (8.2.12.2 b)
  • Over-current and maximum voltage: Determined in consultation with the battery system manufacturer, assuming failure of the external DC power supply. (8.2.12.2 c)
  • Insulation baseline: Measure before the test per Appendix B (clause 6.1.5).

Test parameters

Parameter Value Source
Ambient temperature 20 °C ± 10 °C 8.2.12.2 a)
SOC Mid-SOC (middle of normal operating range) 8.2.12.2 b)
Power source External DC power supply 8.2.12.1
Initial charging current Manufacturer's maximum normal charging current 8.2.12.3 b)
Over-current level Per manufacturer (assuming external DC supply failure) 8.2.12.2 c)
Ramp time (normal → over-current) ≤ 5 s 8.2.12.3 b)
Charging-control communication Changed or disabled to allow over-current 8.2.12.3 a)
Termination conditions Auto cutoff / manufacturer signal / T stable (ΔT < 4 °C over 2 h) 8.2.12.4
Post-test observation 1 h at test environment temperature 8.2.12.5

Procedure

  1. Confirm pre-treatment per 7.2 and measure baseline insulation per Appendix B. (6.1.5)
  2. Adjust SOC to the middle of the normal operating range. (8.2.12.2 b)
  3. Bring ambient to 20 °C ± 10 °C. (8.2.12.2 a)
  4. Connect the external DC power supply equipment.
  5. Change or disable the charging-control communication so the system will accept the over-current level agreed with the manufacturer. (8.2.12.3 a)
  6. Start the external DC supply and charge the battery system at the manufacturer's maximum normal charging current. (8.2.12.3 b)
  7. Within 5 seconds, increase the current from the maximum normal charging current to the agreed over-current level, and continue charging. (8.2.12.3 b)
  8. Continue until any termination condition is met: a. The test object automatically terminates the charging current. b. The test object sends a signal to terminate the charging current. c. The test object's temperature stabilizes (ΔT < 4 °C over 2 h). (8.2.12.4)
  9. Observe at the test environment temperature for 1 hour. (8.2.12.5)
  10. 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. (8.2.12.5)

What changed from GB 38031-2020

  • Listed in the preface change list as both requirements (5.2.12) and method (8.2.12) 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 5-second ramp from max-normal to over-current is fast enough that BMS protection has to react during the ramp or shortly after. Slow-rolling the ramp would let the system de-rate gracefully — the standard explicitly prevents that. Protection logic with a sliding-window current filter slower than 5 s will likely fail this test even if the steady-state over-current eventually trips.

Engineering note (non-normative): The over-current and maximum voltage are negotiated with the manufacturer "assuming failure of the external DC supply" — i.e., the realistic worst case from a faulted DC charger. This is a written agreement that becomes part of the test record. Pick numbers that represent a credible charger-side fault, not the easiest case to pass.