Cell Testing

Cell testing underpins every stage of battery development: from initial characterisation of a new cell candidate, through BMS calibration data acquisition, legislative sign-off, and ongoing validation during production. The tests naturally fall into eight categories:

• Performance Data: electrical performance under controlled conditions including capacity, OCV, impedance, self-discharge, formation, and charge characterisation
• Ageing: calendar and cycle life; the basis for lifetime estimation and SOH modelling
• Diagnostics: non-destructive techniques to detect internal faults and track degradation
• BMS Data: the complete measured dataset required to design and calibrate a battery management system
• Mechanical Tests: structural integrity, swelling, pressure behaviour, vibration, and shock
• Thermal Tests: heat generation, thermal properties, calorimetry, and thermal runaway characterisation
• Abuse Tests: behaviour at and beyond operational limits across electrical, thermal, and mechanical domains
• Legislative / Certification Testing: standards required for transport, sale, and use in global markets

Two companion reference pages run alongside the detail below: Cell Measurement Parameters, an A-to-Z of the parameters referenced throughout, and Cell Measurement Techniques, an index of the measurement techniques and where each is covered in more depth.

Performance Data

Performance data characterises the electrical, thermal, and mechanical outputs of a cell under controlled, repeatable conditions. It provides the foundational dataset for pack sizing, power mapping, and model parameterisation.

Capacity

Battery capacity defines the total charge (Ah) and energy (Wh) available from a cell between its voltage limits.

• Standard Capacity Test (C/5 or C/10 reference discharge)
  • Procedure: Condition at nominal temperature; CC-CV charge to Vmax; rest; CC discharge to Vmin at C/5
  • Outputs: Nominal capacity (Ah), energy (Wh), coulombic efficiency, voltage profile
  • Variants: Different C-rates to characterise rate-dependent capacity loss; temperature variants

• Rate Capability (Ragone Characterisation)
  • Procedure: Repeat discharge at C/5, C/2, 1C, 2C, 3C, 5C, 10C (cell-dependent); recharge between each
  • Outputs: Capacity retention vs. C-rate curve; energy vs. power (Ragone plot)
  • Relevance: Critical for fast-charge applications and power tool / EV peak demand sizing

• Temperature-Dependent Capacity
  • Outputs: Capacity vs. temperature derating curve; input to BMS state-of-energy estimation
  • Range: Typically −40°C to +60°C in 10°C steps; soak time critical to achieve thermal equilibrium

Open Circuit Voltage (OCV)

The OCV curve maps terminal voltage to State of Charge at rest — an essential input for SoC estimation algorithms.

• Quasi-Static OCV (Galvanostatic Intermittent Titration — GITT)
  • Procedure: Applies short current pulses with extended rest; resolves OCV and solid-state Li diffusion coefficient
  • Limitation: Multi-day duration; typically reserved for cell R&D

• Intermittent Current Interruption (ICI)
  • Procedure: Faster GITT alternative; optimises rest duration to balance accuracy vs. test time
  • Advantage: Reduced duration while maintaining modelling accuracy

• Charge / Discharge OCV Averaging
  • Procedure: Slow C/20 or C/50 charge and discharge; average of the two curves used as OCV
  • Notes: Captures OCV hysteresis (significant in LFP chemistry; minimal in NMC)

• Temperature-Dependent OCV
  • Relevance: OCV shifts with temperature (entropic coefficient); needed for accurate cold-start SoC estimation

Measurement of OCV

The measurement of Open Circuit Voltage can be time consuming as it needs to be established versus the State of Charge (SoC) of the cell. Doing this in fine steps from 0% to 100%, with the measurement being made “at rest”, means we have to charge/discharge and then let it rest before making the voltage measurement.

Internal Resistance / Impedance

• DC Internal Resistance (DCIR)
  • Procedure: Hybrid Pulse Power Characterisation: 1C discharge pulse (10 s); voltage drop used to compute R = ΔV/ΔI
  • Matrix: Repeated across SoC (0–100% in 10% steps) and temperature (−20°C to +45°C); charge and discharge separately
  • Outputs: DCIR map; pulse power capability map (W) vs. SoC and temperature — direct input to BMS power limits

• Electrochemical Impedance Spectroscopy (EIS)
  • Procedure: Small AC perturbation (typically 5–10 mV) swept across frequency range (mHz to kHz)
  • Outputs: Nyquist plot; equivalent circuit model components: ohmic resistance (R₀), SEI resistance, charge-transfer resistance, Warburg diffusion element
  • Advantage: Separates contributions from electrolyte, SEI, and electrode kinetics; non-destructive
  • Variants: Temperature-dependent EIS; SoC-dependent EIS; operando EIS during cycling

• AC Resistance (1 kHz)
  • Procedure: Single-frequency AC impedance; rapid production-line compatible measurement
  • Use: Incoming quality control; quick check of weld quality or tab connection integrity

Self-Discharge

Self-discharge is the slow loss of stored energy from a cell at rest, caused by parasitic electrochemical reactions. It is a key parameter for BMS leakage current modelling, shelf-life estimation, and SOH tracking.

• Open-Circuit Voltage Decay Method
  • Procedure: Fully charge cell; rest; measure OCV at defined intervals over 30–90 days; convert OCV to SoC via OCV curve
  • Outputs: Self-discharge rate (%/month); leakage current (µA)
  • → Self-Discharge Test Procedure

• Coulombic Efficiency Method (High Precision Coulometry)
  • Procedure: Precisely measure charge in vs. charge out over a cycle; CE = Qd/Qc
  • Sensitivity: Detects lithium inventory loss and parasitic reactions at the 0.01% level
  • Use: Formation quality check; early-cycle ageing indicator

Formation & Initial Conditioning

Formation is the first charge/discharge cycle applied to a fresh cell to establish the Solid Electrolyte Interphase (SEI) layer on the anode. The quality and stability of the SEI determines long-term coulombic efficiency and cycle life. Test data from formation cycles are an important quality and performance predictor for incoming cell QA.

• Formation Capacity Check
  • Procedure: Slow C/10 first charge followed by C/5 discharge; confirms nominal capacity and formation gas evolution is within spec

• Ultra High Precision Coulometry (UHPC)
  • Procedure: Precisely tracks cumulative charge and discharge over the first 5–15 cycles at constant temperature (±0.005°C)
  • Outputs: Coulombic efficiency trajectory; early indicator of cycle life; detection of lithium plating risk
  • Reference: Dahn group method; increasingly used as incoming QA on incoming cells

Charge Characterisation

Charge characterisation defines the cell’s ability to accept energy at various rates and temperatures. It is directly equivalent to discharge rate characterisation and equally important for BMS charge limit tables, fast-charge protocol design, and system-level energy recovery modelling.

• CC-CV Charge Profile
  • Procedure: Constant Current to Vmax; transition to Constant Voltage until current tapers to C/20 or C/50
  • Outputs: Charge time vs. C-rate; voltage and current profile during CV tail

• Fast Charge Protocols (MCS, XFC)
  • Procedure: Multi-step CC-CV or multi-stage current profiles at high C-rates (3C–6C); temperature-controlled
  • Outputs: Capacity recovered; temperature rise; cycle life impact at elevated charge rate
  • Relevance: EV fast-charge capability development and validation

• Voltage-Temperature Derating for Charging
  • Outputs: Maximum allowable charge current vs. temperature; input to BMS charge current limits

Ageing

Ageing tests quantify how cell performance degrades over time and use. Results feed lifetime prediction models and inform pack control strategy. The page correctly identifies calendar and cycle ageing as the two primary branches; the detail below expands both.

See Cell Ageing Tests for how the calendar and cycle test programmes are set up.

Cycle Ageing

• Standard Cycle Life Test
  • Procedure: Charge and discharge between defined voltage limits at a reference C-rate and temperature; periodic reference performance tests (RPTs) every 50–200 cycles
  • Outputs: Capacity fade curve (Ah retained vs. cycle number); resistance growth; end-of-life definition (typically 80% capacity retention)

• Application-Representative Cycle Ageing
  • Procedure: Real-world or synthetic drive-cycle profiles (e.g. WLTP, ARTEMIS, custom BESS profile) instead of constant C-rate
  • Outputs: Life in equivalent full cycles (EFCs) under representative use

Developing a Lifecycle Test Procedure

One of the first things to do is to break the problem into Calendar and Cycle Ageing.

Each of these can then be tested independently.

• Multi-Stress Cycle Ageing
  • Procedure: Matrix of temperature, SoC window, and C-rate to build a statistical ageing model
  • Outputs: Stress-factor degradation model (e.g. Wang model, Arrhenius fitting, semi-empirical)

• Incremental Capacity Analysis (ICA) / Differential Voltage Analysis (DVA)
  • Procedure: Compute dQ/dV or dV/dQ from slow-rate cycles; track peak shifts and amplitude changes
  • Outputs: Non-destructive diagnosis of Loss of Lithium Inventory (LLI) and Loss of Active Material (LAM) throughout cycling

Calendar Ageing

• Storage at Fixed SoC and Temperature
  • Procedure: Cells held at defined SoC (e.g. 50%, 100%) and storage temperature; capacity and resistance checked at periodic intervals (monthly)
  • Matrix: SoC × temperature factorial; minimum 3 temperatures to enable Arrhenius extrapolation
  • Outputs: Calendar fade model: capacity vs. time; resistance growth vs. time

• Accelerated Calendar Ageing
  • Procedure: Elevated temperature (e.g. 45°C, 60°C) to accelerate degradation; Arrhenius correction applied to extrapolate to operating temperature
  • Caution: High-temperature acceleration may trigger different degradation mechanisms not representative of in-use ageing

Reference Performance Tests (RPTs)

Inserted periodically during ageing programmes to track capacity, resistance, and OCV curve evolution without interrupting the ageing protocol.

• RPT content typically includes: C/5 capacity check; HPPC resistance check; EIS; slow-rate OCV measurement

Teardown Tests

Used to analyse cell chemistry degradation so as to speed up the analysis of cell ageing.

• Titration Gas Chromatography (TGC): Analytical technique used to quantify trace gas species produced by degradation reactions inside a cell.

Diagnostics

Diagnostic testing detects internal faults, manufacturing defects, or in-service degradation without requiring destructive disassembly.

Electrical Diagnostics

• Electrochemical Impedance Spectroscopy (EIS)
  • Application: Non-destructive in-situ analysis of SEI resistance, charge-transfer resistance, and electrolyte resistance; tracks ageing and detects lithium plating

• Relaxation Delta Voltage (RdV)
  • Application: Detection of micro internal short circuits through analysis of the voltage relaxation transient after current interrupt; developed by LG Energy Solution

Relaxation delta Voltage can be used to find micro internal short circuits in cells.

• Self-Discharge Screening
  • Application: Incoming cell QA; detection of latent internal shorts via OCV decay over 48–96 hours

• Ultra High Precision Coulometry (UHPC)
  • Application: Detection of parasitic side reactions and latent defects in early-cycle data
• HiPot Test: a high potential applied across the cell to detect insulation failures and internal short circuits; nondestructive and commonly used in production QC

Imaging & Structural Diagnostics

• X-Ray Computed Tomography (CT Scanning)
  • Application: Non-destructive internal imaging: winding alignment, tab weld quality, separator folds, electrolyte distribution, delamination
  • Resolution: Micro-CT achieves µm-level resolution; suitable for production defect detection and post-abuse analysis

Using CT Scanning to Detect Battery Defects

Battery defects are a major scourge on the industry. In fact, battery defects have been deemed responsible for major billion-dollar electric vehicle recalls.

CT scanning cells is a way of understanding manufacturing quality issues.

• Neutron Imaging
  • Application: Lithium distribution mapping within electrodes (lithium is opaque to neutrons but transparent to X-ray)
  • Facility: Requires neutron source (typically at national nuclear research facilities)

• Ultrasonic / Acoustic Testing
  • Application: Acoustic transmission through the cell; detects gas pockets, delamination, and electrolyte distribution changes non-destructively
  • Advantage: Suitable for in-line or in-situ monitoring without specialist facilities

BMS Characterisation Data

In order to design and calibrate the BMS to work with a particular battery cell, a comprehensive measured dataset is required — often called the Cell Characterisation Dataset or Cell Model Dataset. This data must be acquired experimentally for the specific cell being used; datasheet values are insufficient for production-quality BMS calibration.

State Estimation Inputs

• OCV–SoC Curve (bi-directional, multi-temperature)
  • Use: SoC estimation lookup table (Coulomb counting + OCV correction); charge / discharge hysteresis map

• DCIR Map (SoC × Temperature × Direction)
  • Use: State of Power (SoP) estimation; voltage prediction under load; thermal model heat source term Q = I²R

• EIS Equivalent Circuit Model Parameters
  • Use: Dynamic voltage model (RC pair time constants); SoC and temperature dependent parameter tables

Operational Limits

• Voltage Limits (Vmin, Vmax) vs. Temperature
  • Use: BMS cut-off thresholds; safe operating area definition

• Current Limits (Imax charge / discharge) vs. SoC and Temperature
  • Use: BMS current de-rating tables; peak power limits

• Temperature Limits (operating and storage)
  • Use: Thermal management set-points; charge inhibit thresholds at low temperature

Thermal Model Inputs

• Specific Heat Capacity (Cp) vs. Temperature
  • Use: Cell thermal mass in lumped-parameter or FEA thermal model

• Thermal Conductivity (axial and radial)
  • Use: Heat flow through cell body; critical for wound cylindrical and prismatic cells

• Entropic Coefficient (∂OCV/∂T)
  • Use: Reversible heat term in thermal model; significant in LFP

• Heat Generation Rate vs. C-rate and SoC
  • Use: Calorimetry-derived; direct input to thermal model heat source

Ageing / SOH Model Inputs

• Capacity Fade Model Parameters
  • Use: SOH estimation; remaining useful life (RUL) prediction

• Resistance Growth Model Parameters
  • Use: Dynamic power limit adjustment as cell ages

Mechanical Tests

The battery cell is a complex electro-chemo-mechanical system. Mechanical characterisation informs structural pack design, predicts behaviour under shock and vibration, and ensures cells maintain performance under the compressive loads imposed by module assembly.

Structural / Component Tests

• Separator Tensile Strength and Elongation
  • Procedure: Tensile testing to failure at defined strain rate; machine direction and transverse direction
  • Relevance: Separator mechanical integrity under jelly-roll winding tension and cell swelling
  • Relevance: Fracture of foil during cycling (fatigue crack growth from electrode particle cracking) contributes to capacity loss

• Current Collector Foil Tensile Testing
  • Procedure: Tensile test on Cu (anode) and Al (cathode) foils; typically 6–12 µm thick
  • Outputs: Young’s modulus, yield strength, UTS, elongation at break

Cell Component Mechanical Tests

Cell component mechanical tests are extensive and required in order that a more detailed understanding of how the cells behave can be established. The battery cell is a complex: chemistry, electrical, thermal and mechanical system. Cycle ageing is seen as a deteriation in the chemistry of the cell, but should also be considered as a mechanical system. Expanding and contracting through charging and discharging that leads to fracturing.

Image shows tensile testing of 6µm thick copper foil.

• Electrode Coating Adhesion (Peel / Scratch Test)
  • Procedure: 90° peel test of dried electrode coating from current collector
  • Outputs: Adhesion force (N/m); sensitivity to binder content and drying conditions

• Cell Crush / Indentation Test
  • Procedure: Quasi-static crush with flat plate, hemisphere, or rod indentor; force and displacement monitored
  • Outputs: Force at short circuit / thermal event initiation; mechanical abuse threshold
  • Note: Overlaps with abuse testing; distinguishes mechanical failure mode from electrical

Pressure / Swelling

• In-Operando Pressure Mapping (Pouch Cells)
  • Procedure: Thin-film pressure sensor array placed between cell and compression fixture; measured through charge/discharge
  • Outputs: Pressure distribution map; peak and mean pressure vs. SoC; cycle-to-cycle growth
  • Relevance: Inhomogeneous pressure accelerates localised ageing; fixture design critical for pouch module

Pressure Mapping

An inhomogeneous pressure distribution can lead to accelerated ageing and cell failure, due to locally high pressure. This can arise from unevenness in electrode coatings or other jelly roll components, but can also be an effect of imperfections in the cell fixture. Even minor tilting of the plates leads to zones with higher and lower pressures, and is exacerbated by thermal expansion and contraction. 

• Cell Swelling / Thickness Measurement
  • Procedure: Dilatometry or laser displacement sensor to track cell thickness or diameter vs. SoC and temperature; through-life tracking
  • Outputs: Reversible (SoC-dependent) and irreversible (age-dependent) swelling data
  • Relevance: Module design gap allocation; contact pressure maintenance over life

• Stack Pressure Measurement (Prismatic Cells)
  • Procedure: Load cell or pressure sensor in constrained stack; monitors clamping load evolution
  • Relevance: Jelly-roll expansion exerts force on prismatic housing; lid deflection and weld fatigue risk

Vibration

Vibration testing replicates the mechanical environment a cell experiences during vehicle operation or transport. Both sinusoidal and random vibration profiles are applied to verify that internal connections, tab welds, and electrode stack integrity are maintained throughout the expected service life.

• Sine Sweep Vibration
  • Standard: IEC 62660-2; UN 38.3 T.3; ISO 12405-2
  • Procedure: Cell mounted to vibration table; sinusoidal excitation swept through frequency range (10–150 Hz) in X, Y, Z axes
  • Outputs: Pass/fail vs. voltage and visual inspection criteria; resonance frequencies

• Random Vibration
  • Standard: SAE J2380; IEC 62660-2
  • Procedure: PSD profile representative of vehicle road load applied for defined duration; accelerometer on cell
  • Relevance: Representative of EV lifetime vibration environment; more damaging than sine sweep for some failure modes

• Post-Vibration Capacity and DCIR Check
  • Procedure: RPT after vibration test confirms no capacity loss or resistance increase from loose internal connections

Mechanical Shock

Shock testing simulates impact events during handling, transport, or vehicle collision scenarios. It is distinct from vibration in that the energy is delivered in a short, high-amplitude pulse rather than a sustained oscillation. Pass/fail criteria focus on maintaining electrical integrity and preventing internal short circuits.

• Half-Sine Shock Pulse
  • Standard: IEC 62660-2; UN 38.3 T.4
  • Procedure: Cell subjected to defined peak deceleration (e.g. 150 g, 6 ms half-sine) in X, Y, Z axes; repeated
  • Outputs: Pass/fail on voltage, capacity, and visual; typically 3 shocks per axis = 18 total

• Drop Test
  • Standard: IEC 62133; UN 38.3 T.4
  • Procedure: Free-fall drop from 1 m onto hard surface in defined orientations
  • Relevance: Consumer cell / portable application certification; detects terminal or casing damage

Thermal Tests

Thermal testing characterises both the fundamental thermal properties of a cell and its behaviour under extreme thermal conditions including thermal runaway.

Calorimetry

What is Calorimetry?

Calorimetry is a branch of thermodynamics that deals with heat transfer quantification. Heat can be transferred during a variety of processes, such as chemical reactions, phase changes, or dissolution of solutes in a solvent. Calorimetry follows the first law of thermodynamics, which states that energy cannot be created or destroyed, only transferred. The direction that the heat takes will determine the type of process: if heat is absorbed, the process will be endothermic, whereas if heat is released, the process will be exothermic.

• Accelerating Rate Calorimetry (ARC)
  • Procedure: Adiabatic calorimeter; cell self-heats until exothermic reactions accelerate; tracks temperature and rate of rise (dT/dt)
  • Outputs: Onset temperature of self-heating; maximum self-heating rate; heat-wait-seek protocol
  • Relevance: Thermal runaway characterisation; safety assessment; TR trigger temperature

• Isothermal Micro-Calorimetry
  • Procedure: Measures extremely small heat flows (µW range) at fixed temperature
  • Outputs: Parasitic reaction heat at rest and during cycling; early ageing indicator

• Isobaric Calorimetry / Battery Calorimeter
  • Procedure: Cell cycled inside calorimeter at defined C-rate; heat flow integrated over time
  • Outputs: Total heat generation (J); heat generation rate (W) vs. SoC; irreversible (Joule) and reversible (entropic) heat separation

See Calorimetry for more on calorimeter types, including accelerated-rate calorimetry.

Thermal Properties

• Specific Heat Capacity (Cp)
  • Procedure: Adiabatic calorimeter or DSC on cell sample; temperature-step method
  • Outputs: Cp in J·kg⁻¹·K⁻¹ vs. temperature; required for thermal model
  • Note: you can initially use a generic specific heat capacity for a cell to do some initial thermal modelling. However, the heat capacity of a cell varies enough with chemistry and design that it is worth measuring it for the specific cell you are using. This will allow you to develop more accurate thermal models of the cell.

Measuring Specific Heat Capacity

• Sample Container: At the heart of the chamber is a sample container where the material under investigation is placed. 
• Temperature Sensors: The chamber is equipped with fast response thermocouples to monitor the temperature of the sample continuously.
• Heating System: A resistive heating system surrounds the chamber, capable of precisely controlling the temperature of the sample according to the experimental protocol.
• Insulation: The entire assembly is heavily insulated to ensure adiabatic conditions, meaning that once the external heating is stopped, no heat should enter or leave the system.

• Thermal Conductivity
  • Procedure: Laser flash method (through-plane) and hot-disk / steady-state (in-plane)
  • Values: Typical: 0.3–1.0 W·m⁻¹·K⁻¹ through-plane; 20–40 W·m⁻¹·K⁻¹ in-plane (dominated by metal foils)
  • Outputs: Anisotropic thermal conductivity tensor; essential for accurate thermal model

• Entropic Coefficient (∂OCV/∂T)
  • Procedure: OCV measured at same SoC point across a temperature range (typically 10°C to 40°C)
  • Outputs: Reversible heat contribution; important in LFP where entropic heat can exceed Joule heating

• Thermal Impedance Testing
  • Procedure: Apply known heat source to cell surface; measure temperature response; fit to thermal model
  • Outputs: Cell-to-surface thermal resistance; useful for contact resistance quantification

Thermal Cycling

• Thermal Cycling / Thermal Shock
  • Standard: IEC 62660-2; UN 38.3 T.2; ISO 12405-2
  • Procedure: Repeated temperature cycling between low and high extremes (e.g. −40°C to +85°C); cell monitored for voltage, leakage, and physical integrity
  • Outputs: Pass/fail on capacity retention and visual inspection after cycling

Environmental Tests

Environmental tests assess how the cell tolerates the climatic and physical environment it will see in transport, storage, and service — separate from the electrical, thermal, and mechanical abuse tests below.

Altitude Simulation

• Method: Low-pressure chamber test at or below 11.6 kPa for at least six hours at ambient temperature
• Scope: Simulates unpressurised air cargo hold conditions; required for all cells and batteries under UN/DOT 38.3 (see Legislative Testing, below)

Humidity / Damp Heat

• Method: Steady-state or cyclic damp-heat exposure per IEC 60068-2 climatic test series
• Scope: Terminal and casing corrosion, seal integrity, and insulation resistance degradation under humid storage or operating conditions

Salt Spray / Corrosion

• Method: Salt-fog exposure per IEC 60068-2-11 or ASTM B117
• Scope: Terminal and casing corrosion resistance for marine, coastal, and de-icing-salt road environments; commonly specified for EV and stationary storage enclosures

Dust Ingress (IP Rating)

• Method: Dust-chamber exposure per the IEC 60529 IP rating system
• Scope: Confirms enclosure sealing prevents dust ingress that could cause internal short circuits or block venting paths

Immersion / Water Ingress

• Method: Static or dynamic immersion per the IEC 60529 IP rating system (IPX7/IPX8), or the immersion test in UL 2580
• Scope: Confirms no water ingress under flooding or wading conditions; particularly relevant for underbody-mounted EV packs and outdoor BESS enclosures

These are rarely tested in isolation: UL 2580, IEC 62619, and GB 38031 each specify combinations of the environmental tests above alongside the mechanical, thermal, and electrical tests already covered.

Abuse Tests

Abuse tests establish how a cell behaves at and beyond its safe operating boundaries. Results inform safety system design, fusing, thermal management, and legislative compliance.

Electrical Abuse

• Nail Penetration (Internal Short Circuit)
  • Severity: Highest heat generation rate of all cell-level abuse tests
  • Outcome classification: No event / venting / fire / explosion
  • Nail Test – perhaps the most severe cell test with the highest rate of heat production.

• External Short Circuit
  • Procedure: Defined resistance (≤5 mΩ or as per standard) applied across terminals
  • Standard: UN 38.3 T.5; IEC 62133; UL 2054

• Overcharge
  • Procedure: Charge at defined current to 1.5× or 2× Vmax or until event
  • Standard: UN 38.3 T.7; IEC 62133; UL 2054

• Over-Discharge / Forced Discharge
  • Procedure: Discharge beyond Vmin; for series strings, reverse-charge a weaker cell
  • Relevance: Pack-level risk when cells are unbalanced; copper dissolution and re-deposition risk

Thermal Abuse

• Thermal Stability (Oven / Furnace Test)
  • Procedure: Charged cell placed in oven ramping to ≥150°C; monitors for event
  • Standard: UN 38.3 T.2; IEC 62133; UL 2054

Thermal Runaway

Thermal runaway occurs when exothermic reactions within the cell generate heat faster than it can be dissipated, leading to a self-sustaining temperature escalation. Characterising the trigger conditions, progression rate, and outputs (gas species, peak temperature, energy release) is essential for pack-level safety system design and regulatory compliance.

• Nail Penetration Test
  • Procedure: Conductive nail driven through fully-charged cell at defined rate; triggers internal short
  • Outputs: Temperature profile; peak temperature; vent / fire / explosion outcome; test time to runaway
  • Standard: Referenced in GB/T 31485, IEC 62619, GTR 20

• External Short Circuit Thermal Response
  • Procedure: Low-resistance external short applied to fully-charged cell at defined temperature
  • Outputs: Peak temperature; current profile; thermal runaway threshold (if any)

• Overcharge Thermal Response
  • Procedure: Cell charged beyond Vmax until thermal event occurs; records temperature and voltage
  • Standard: IEC 62133; UL 2054; UN 38.3 T.7

• Forced Thermal Runaway (TR Propagation Testing)
  • Procedure: Cell heated by external heater until runaway triggers; also used to characterise gas emission species
  • Outputs: Trigger temperature; heat-to-vent time; gas emission volume and composition (HF, CO, CO₂, H₂)

Mechanical Abuse

• Crush Test (Flat Plate / Hemispherical Indentor)
  • Standard: SAE J2464; IEC 62660-2

• Drop Test
  • Standard: IEC 62133; UN 38.3 T.4

• Penetration (Non-conductive — Blunt Force)
  • Procedure: Blunt non-conductive object driven into cell to simulate impact without electrical short

• Immersion / Water Ingress
  • Standard: IEC 62133; UL 2054
  • Procedure: Cell submerged in water for defined duration; tests case seal integrity

Legislative Testing

Legislative tests are required to prove a cell is safe for transport, sale, and use in defined markets. The key standards are summarised below.

Transport Certification

• UN/DOT 38.3 (UN Manual of Tests and Criteria, Part III, §38.3)
  • Scope: Mandatory globally for air, sea, road, and rail shipment of lithium cells and batteries
  • Test series: T.1 Altitude simulation; T.2 Thermal test; T.3 Vibration; T.4 Shock; T.5 External short; T.6 Impact/crush; T.7 Overcharge; T.8 Forced discharge

Product Safety

• IEC 62133-2 (Portable Sealed Cells — Lithium)
  • Scope: Safety requirements for portable sealed secondary lithium cells; mandated by many IEC end-device standards (IEC 62368-1 etc.)

• UL 2054
  • Scope: North American household and commercial battery standard; mandated by a number of U.S. end device standards

• IEC 62660-2 (Performance and Reliability for EV Applications)
  • Scope: Lithium-ion cells for propulsion of EVs: reliability and abuse testing

• GB/T 31485 / GB/T 31241 (China)
  • Scope: Mandatory Chinese national standard for EV traction and portable cells respectively

EU Battery Regulation (2023/1542)

The EU Battery Regulation came into force in August 2023 and is being phased in from 2024 onwards. It introduces performance, durability, and sustainability requirements that go significantly beyond previous EU battery directives and have direct implications for cell-level testing and data reporting for any cells placed on the EU market.

• Performance and Durability Requirements
  • Scope: Minimum capacity retention thresholds, fade limits, and declared rated capacity accuracy

• State of Health (SOH) Accessibility
  • Scope: Battery passport requirement; SOH must be readable from BMS

See also: Cell Legislation, Cell Capacity Testing: Standards, Diagnostics and Safety, Pack Testing, Isolation Tests on Assembled Cells, Self-Discharge Test Procedure