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Over-discharge (cell)

Verifies a fully discharged cell driven further below its termination voltage at 1C does not catch fire or explode.
Clause (method) 8.1.2
Clause (pass criteria) 5.1.1
Object cell
Status vs. 2020 revised (method only)
Observation period 1 h at test environment temperature

Pass criteria

A battery cell, after undergoing the over-discharge test according to 8.1.2, should not catch fire or explode.

There is no insulation requirement and no leakage/housing-crack requirement at cell level. (PDF p. 11)

Source: GB 38031-2025, clause 5.1.1 (PDF p. 11).

Pre-conditions

  • Sample: A battery cell. (8.1.2.1)
  • Active protection: Any additional active protection circuits or devices on the cell are removed. (8.1.1)
  • Starting state: Cell adjusted to its discharge termination voltage as specified by the manufacturer. (8.1.2.2)

Test parameters

Parameter Value Source
Starting voltage Discharge termination voltage (manufacturer-specified) 8.1.2.2
Discharge current I1 (1-hour-rate current, numerically equal to rated capacity) 8.1.2.2 / 4.1
Discharge duration 30 min 8.1.2.2
Observation period 1 h at test environment temperature 8.1.2.3

Procedure

  1. Confirm the test object is a single battery cell with active protection devices removed. (8.1.1, 8.1.2.1)
  2. Adjust the cell's state-of-charge to the discharge termination voltage. (8.1.2.2)
  3. Discharge the cell at a current of I1 for 30 min. (8.1.2.2)
  4. After the discharge step, observe the cell for 1 h at the test environment temperature (22 °C ± 5 °C, per 6.1.1). (8.1.2.3)
  5. Record any fire or explosion event during the discharge or the observation window.

After-test observation

Observe the test object for 1 h at the test environment temperature. (8.1.2.3)

What changed from GB 38031-2020

  • The test method was revised vs. the 2020 edition (8.1.2). The pass criterion (5.1.1) was not listed in the preface change list, so the requirement itself is unchanged.
  • (Source: GB 38031-2025 preface, PDF p. 6.)

Migration impact: Cells previously certified under the 2020 method should be re-tested under the 2025 method ahead of the 2026-07-01 effective date for new type approvals.

Engineering notes (non-normative)

Engineering note (non-normative): "Discharge termination voltage" is whatever the manufacturer declares — there is no universal floor. Confirm the value in the cell datasheet before adjusting SOC, and log it in the test report so the over-discharge depth is reproducible.

Engineering note (non-normative): Discharging at I1 for 30 min after reaching termination voltage drives the cell well into reversal. Expect cell voltage to swing negative; a four-quadrant supply is needed to maintain constant current through the polarity inversion.