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Safety after fast-charge cycles (cell)

Verifies that a cell capable of charging from 20 % to 80 % SOC in ≤ 15 min still survives an external short-circuit after 300 such fast-charge cycles. New in GB 38031-2025.
Clause (method) 8.1.8
Clause (pass criteria) 5.1.7
Object cell
Status vs. 2020 new
Observation period 1 h at test environment temperature (per the embedded 8.1.4 step)

Pass criteria

A battery cell, after undergoing the safety test following fast charge cycles according to 8.1.8, should not catch fire or explode.

The pass criterion attaches to the external short-circuit step that terminates the procedure. There is no insulation requirement and no leakage/housing-crack requirement at cell level. (PDF p. 11)

Source: GB 38031-2025, clause 5.1.7 (PDF p. 11).

Pre-conditions

  • Sample scope: A battery cell capable of charging from 20 % SOC to 80 % SOC with a total charging time not exceeding 15 min. Cells charged only through vehicle energy are excluded. (8.1.8.1)
  • Active protection: Any additional active protection circuits or devices on the cell are removed. (8.1.1)

Test parameters

Parameter Value Source
Cell scope Capable of 20 % → 80 % SOC in ≤ 15 min total charging time (excludes vehicle-energy-only cells) 8.1.8.1
Cycle start SOC 20 % 8.1.8.2 a)
Cycle end SOC 80 % 8.1.8.2 c)
Charge time per cycle ≤ 15 min 8.1.8.2 c)
Rest after SOC adjust / charge 30 min (or mfr-specified) 8.1.8.2 b), d)
Number of cycles 300 8.1.8.2 e)
Terminating test External short-circuit per 8.1.4 8.1.8.2 f)
Observation period 1 h at test environment temperature (per 8.1.4.4) 8.1.4.4

Procedure

  1. Confirm the cell is in scope: it can be charged from 20 % to 80 % SOC in ≤ 15 min, and is not a vehicle-energy-only cell. (8.1.8.1)
  2. Adjust the cell to 20 % SOC using the manufacturer-provided method. (8.1.8.2 a)
  3. Let the cell stand for 30 min (or the manufacturer-specified time). (8.1.8.2 b)
  4. Charge the cell using the manufacturer-provided method to 80 % SOC, with charging time ≤ 15 min. (8.1.8.2 c)
  5. Let the cell stand for 30 min (or the manufacturer-specified time). (8.1.8.2 d)
  6. Repeat steps 2–5 for a total of 300 cycles. (8.1.8.2 e)
  7. Perform the external short-circuit test according to 8.1.4 on the cycled cell: standard charge per 7.1.1, short the terminals through < 5 mΩ for 10 min, then observe for 1 h. (8.1.8.2 f, 8.1.4)
  8. Record any fire or explosion event during the 8.1.4 step or its 1 h observation window.

After-test observation

Observe the test object for 1 h at the test environment temperature, as required by the embedded external short-circuit step. (8.1.4.4)

What changed from GB 38031-2020

This test did not exist in GB 38031-2020. Added in the 2025 revision as part of a new requirements + method pair (5.1.7 and 8.1.8) covering safety after fast-charge cycling. (Source: GB 38031-2025 preface, PDF p. 5.)

Migration impact: Cells marketed as supporting 20→80 % SOC in ≤ 15 min must pass this 300-cycle + external-short sequence to be type-approved under the 2025 standard. Cells without that fast-charge capability are out of scope and need not undergo it.

Engineering notes (non-normative)

Engineering note (non-normative): 300 cycles at "≤ 15 min charge + 30 min rest" (and an equivalent discharge-from-80%-to-20% leg, however it is implemented to set up step a) gives a minimum on-test time of roughly 5–7 days continuous before the terminating short. Plan instrumentation lifetime, data-logging capacity, and safety-cell isolation accordingly.

Engineering note (non-normative): The standard does not specify the discharge path that brings the cell back from 80 % to 20 % between cycles — only step (a) "adjust to 20 % SOC". A reasonable approach: discharge at the manufacturer's normal-use rate (e.g., I3) to 20 % SOC. Document the discharge method in the test report; reviewers will ask.

Engineering note (non-normative): The external short (8.1.4) is performed at standard charge (per 8.1.4.2), not at the 80 % SOC reached at the end of the cycling. Don't skip the recharge step between cycle 300 and the short.