Battery engineering glossary.

Complex voltage-to-current response measured with a stated alternating excitation and frequency.

Alternating-current internal resistance measured with a small AC stimulus at a stated frequency.

Battery management system: measurement, protection, estimation and control functions for cells and the complete pack.

Charge or discharge current expressed relative to rated capacity; 1C equals the rated ampere-hour capacity in amperes.

The mechanical features that locate cells and carry service loads without relying on electrical tabs or wiring.

The charger condition that ends or reduces charge after the required voltage, current, time or state criterion is reached.

The shortest distance through air between conductive parts at different electrical potentials.

The records and approvals that keep drawings, software, components and process revisions tied to a defined product build.

Specify the domain: electrical contact resistance is measured in ohms; thermal contact resistance in K/W (or area-normalized m²·K/W). They describe different losses and heat-transfer limits.

An electrically controlled switch used to connect or isolate a high-current DC path.

A process-capability index comparing specification width with short-term process spread, without accounting for centering.

A process-capability index that also accounts for how the process mean is positioned between specification limits.

The shortest distance along an insulating surface between conductive parts at different electrical potentials.

The DC bus between power-conversion stages, often containing capacitance that creates inrush during connection.

Direct-current internal resistance derived from the voltage change produced by a defined current step and time interval.

The charge removed from a battery relative to a defined capacity basis, usually expressed as a percentage.

Design failure mode and effects analysis: a structured review of design failure modes, effects, causes and controls.

The sequence and duration of operating states, loads, rests and charging that defines battery use.

Electrochemical impedance spectroscopy: measurement of complex impedance over a defined frequency range and operating condition.

The agreed condition at which capacity, resistance, power, safety margin or another requirement no longer meets service limits.

End-of-line testing performed on a finished unit before production release.

A lumped electrical model used to approximate measured battery behavior over a stated range; fitted elements are model parameters, not automatically unique physical components.

Equivalent series resistance. In battery work the term is incomplete unless the instrument, frequency or time and derivation are stated.

The share of units that pass the defined process or test without rework or retest.

A measurement using separate current-force and voltage-sense conductors to reduce lead and contact voltage-drop error.

Hybrid Pulse Power Characterization: controlled discharge and regenerative pulses repeated across a battery operating window to derive time-defined resistance and power capability.

Current squared integrated over time; used when evaluating fuse heating and pulse withstand.

An IEC safety standard for portable sealed secondary lithium cells and batteries.

An IEC safety standard for secondary lithium cells and batteries used in industrial applications.

Resistance between a high-voltage circuit and the chassis or another isolated conductive boundary.

A four-wire measurement arrangement that separates current-carrying leads from voltage-sense leads.

A non-negative parameter that quantifies the dispersion of values attributed to the quantity being measured, based on the available information. State whether the value is standard uncertainty u or expanded uncertainty U, and give the coverage factor when applicable.

Definition reference: JCGM VIM 2.26

A semiconductor switching device commonly used in battery charge and discharge paths.

Nonconformance report: a controlled record of a result that does not meet a specified requirement.

Open-circuit voltage measured with no external load after a stated rest condition.

The terminal voltage measured with no external load after a stated rest condition.

A diagnostic used to identify an interrupted cell-sense or temperature-sense connection.

Cell balancing that dissipates energy from selected cells, usually through resistors. Selection by relative voltage is common, but depends on the control algorithm and operating conditions.

Process failure mode and effects analysis: a structured review of manufacturing failure modes, effects, causes and controls.

Time-dependent departure of electrode potentials from equilibrium while current flows, produced by reaction and transport limitations.

The complete electrical route between cells, protection devices, switching, connectors, conductors and the load or charger.

A controlled initial connection that limits current while downstream capacitance charges before the main path closes.

Electrical power delivered or accepted for a defined short duration under stated voltage, current, SOC and temperature limits.

Pulse-width modulation: control by varying the on-time of a repeating switched signal.

The on-state drain-to-source resistance of a MOSFET under stated gate, current and temperature conditions.

Operation in which a motor drive returns energy to the DC bus and potentially to the battery.

Current flowing opposite to the intended normal direction through a power path or protection stage.

The root-mean-square of current over a defined interval. It gives equivalent resistive heating when resistance is constant over that interval.

The voltage, current and time combinations within which a semiconductor is specified to operate safely.

Loss of stored charge while a cell or battery is disconnected from an external load.

A calibrated low-resistance element used to infer current from its measured voltage drop.

State of charge: an estimate of remaining charge relative to a defined usable capacity.

State of health: an estimate of battery degradation relative to defined capacity, resistance, power or other life criteria.

Motor current when the shaft is prevented from rotating under the stated supply conditions.

Controlled space or compliance provided for cell dimensional change over charge, temperature and life.

The defined cell or battery design represented by the samples used for a transport or safety test program.

Spatial rate of temperature change, expressed for example in K/m. Pack temperature spread is the maximum minus minimum temperature, in K or °C.

A material placed between surfaces to improve and control heat transfer across their interface.

A calculation or simulation that connects heat generation, material properties and boundary conditions to temperature over time.

Self-accelerating cell heating from internal reactions when heat generation exceeds heat removal; it can lead to gas release, fire and propagation to adjacent cells.

A parameter describing the rate at which a first-order electrical or thermal response approaches a new state.

The combined dimensional variation of parts and assembly features across an interface or chain of interfaces.

The ability to connect a product or measurement to its materials, process, equipment, revision and records.

The United Nations transport test requirements for lithium cells and batteries in the Manual of Tests and Criteria.

Energy available between defined operating limits under stated load, temperature, age and reserve conditions.

Release of gas from a cell or enclosure. The mechanism depends on construction: a designed pressure-relief feature, an opening seal or a ruptured pouch; pack-level gas management is a separate design task.

A table linking each requirement to its verification method, evidence, result and status.

The reduction in terminal voltage under load caused by cell behavior and losses through the complete current path.