Glossary¶

All terms below are reproduced from GB 38031-2025, Section 3 (Terms and Definitions). Where the standard cross-references another document (e.g., GB/T 19596 for general EV terminology), the source is noted.

Terms marked 🆕 are new in 2025; ✏️ were revised from the 2020 edition.

Battery cell¶

The basic unit device that converts chemical energy to electrical energy.

It typically includes electrodes, separators, electrolytes, enclosures, and terminals, and is designed to be rechargeable. (GB 38031-2025, 3.1)

Battery module¶

A combination of one or more battery cells connected in series, parallel, or series-parallel configurations to be used as a power source.

(3.2)

Battery pack¶

A unit that obtains electrical energy from the outside and is capable of outputting electrical energy to the outside.

It typically includes battery cells, battery management modules (excluding the BCU), battery enclosures, and related accessories (cooling components, connecting cables, etc.). (3.3)

Battery system¶

An energy storage device consisting of one or more battery packs and related accessories (management systems, high-voltage circuits, low-voltage circuits, and mechanical assemblies, etc.).

(3.4)

Battery subsystem 🆕¶

A collection of any energy storage components formed from the components of a battery pack or system.

(3.5)

Engineering note (non-normative): The subsystem definition was added in 2025 to formalize a practice already common in test labs: when a full pack is too large or massive for a given test rig, a representative subsystem can be used. See Using a subsystem for the conditions under which this is permitted (clause 6.1.6).

Battery electronics¶

Electronic devices that collect or simultaneously monitor electrical and thermal data from the battery pack.

May include cell controllers and electronic components used for balancing between battery cells. (3.6)

Battery control unit (BCU)¶

An electronic device that controls, manages, monitors, or calculates parameters related to the electrical and thermal characteristics of the battery system and provides communication between the battery system and other vehicle controllers.

(3.7)

Rated capacity¶

The capacity value of a battery cell, module, battery pack, or system measured under the manufacturer's specified conditions and declared by the manufacturer.

Typically expressed in ampere-hours (Ah) or milliampere-hours (mAh). (3.8)

Practical capacity¶

The capacity value released from a fully charged battery cell, module, battery pack, or system under the manufacturer's specified conditions.

(3.9)

State-of-Charge (SOC)¶

The percentage of the practical capacity that can be released from the current battery cell, module, battery pack, or system under the manufacturer's specified discharge conditions.

(3.10)

Explosion¶

The sudden release of energy sufficient to generate a pressure wave or projectiles.

The pressure wave or projectiles may cause structural or physical damage to the surrounding area. (3.11)

Fire¶

A sustained combustion (flame duration greater than 1 second) occurring in any part of the battery cell, module, battery pack, or system.

The duration of the flame exceeding 1 second refers to the duration of a single flame, not the cumulative duration of multiple flames. The judgment is made visually without dismantling the test object. Sparks and arcing do not constitute combustion. (3.12)

Housing crack (Gehäuseriss)¶

A mechanical damage to the battery cell, module, battery pack, or system housing caused by internal or external factors, resulting in the exposure or spillage of internal substances.

(3.13)

Leakage ✏️¶

The phenomenon where visible substances leak from the battery cell, module, battery pack, or system to the outside of the test object.

Visible substances are judged visually without dismantling the test object. (3.14 — definition revised in 2025)

Thermal event 🆕¶

A phenomenon where the temperature inside the battery pack or system is significantly higher than the highest operating temperature (as defined by the manufacturer).

(3.15)

Engineering note (non-normative): "Thermal event" is the trigger for the 5-minute warning required by clause 5.2.7 b) 2). The manufacturer defines the alarm parameters (e.g., temperature, dT/dt, voltage drop) and the thresholds at which the warning fires. See The 5-minute thermal warning rule.

Thermal runaway¶

A phenomenon where the temperature of the battery cell uncontrollably rises due to a heat release chain reaction.

(3.16)

Thermal propagation¶

A phenomenon where thermal runaway of one battery cell triggers thermal runaway of the remaining battery cells in the battery pack or system.

(3.17)

End-of-charge voltage¶

The maximum voltage allowed for a battery cell, module, battery pack, or system to reach during charging under the conditions specified by the manufacturer.

(3.18)

End-of-discharge voltage¶

The minimum voltage allowed for a battery cell, module, battery pack, or system to reach during discharging under the conditions specified by the manufacturer.

(3.19)

Body frame¶

The spatial frame structure that ensures the strength and rigidity of the vehicle body.

(3.20, sourced from GB/T 4780—2020, 4.4.3)

Engineering note (non-normative): When a battery pack is enclosed by the vehicle body frame, clause 6.1.3 permits testing with the body frame in place. See Testing with the vehicle body.

Battery management system (BMS)¶

Not formally defined in GB 38031-2025 but referenced repeatedly (e.g., clause 9.1 j on same-type determination). The BMS is the electronic system that manages a battery pack — typically responsible for SOC estimation, cell balancing, thermal management commands, and protection-circuit logic. Its hardware specifications and software version are part of what defines a "same type" pack under clause 9.1 j.

See also: BCU (Battery Control Unit) — the higher-level controller that the BMS may communicate with.

IPX7¶

A water-ingress protection rating defined in GB/T 4208—2017 (the IP Code). IPX7 specifies "protection against the effects of temporary immersion in water" — typically immersion to a depth of 1 m for 30 min, or per the depth/time conditions in §14.2.7 of the IP Code.

Used in GB 38031-2025 Immersion test (8.2.6), Method 2: the test object must meet IPX7 requirements when fully immersed in fresh water for 30 minutes (with depth-vs-pack-height rules per 8.2.6.2 b).

Insulation resistance¶

The electrical resistance between the battery pack/system's positive and negative output terminals and the electric platform (typically the conductive outer enclosure, connected to the vehicle's electric platform).

GB 38031-2025 sets thresholds in clause 5.2.x:

≥ 100 Ω/V (DC circuits)
≥ 500 Ω/V if an AC circuit is present

Measurement procedures are defined in Appendix B. See Insulation resistance procedure and Insulation resistance thresholds.

Test environment temperature¶

The default test environment per clause 6.1.1: 22 °C ± 5 °C, relative humidity 10 %–90 %, atmospheric pressure 86–106 kPa. Most observation periods after testing are conducted at this temperature.

Some tests override this (e.g., 8.2.7.1 external fire requires ambient > 0 °C with wind ≤ 2.5 km/h; 8.2.10 high altitude uses 61.2 kPa). When a test page does not state otherwise, the 6.1.1 defaults apply.

I₁, I₃¶

Discharge-current symbols defined in clause 4.1. I₁ is the 1-hour rate (numerically equal to the rated capacity in A); I₃ is the 3-hour rate (one-third of the rated capacity).

See Symbols and abbreviations for details and the engineering note on C-rate equivalence.

Source: GB 38031-2025, Section 3 (PDF p. 9–11) for formally defined terms. Cross-references from elsewhere in the standard (BMS in 9.1 j; IPX7 in 5.2.6 via GB/T 4208—2017; insulation thresholds in 5.2.x; environment in 6.1.1; symbols in 4.1) included for navigation. General EV terminology cross-referenced from GB/T 19596 (Section 2, Normative References).