{ "node": { "id": "term:acir", "type": "Term", "label": "AC internal resistance", "properties": { "id": "acir", "name": "AC internal resistance", "abbr": "ACIR", "aka": [ "1 kHz impedance" ], "section": "topic-testing", "definition": "The magnitude of a cell’s impedance at one fixed frequency, usually 1 kHz, measured in a second with a small alternating signal. It captures mostly the ohmic resistance, so it is quick for production sorting but blind to interfaces and diffusion.", "unit": "mΩ", "related": [ "dcir", "internal-resistance", "electrochemical-impedance-spectroscopy", "end-of-line-testing" ], "url": "https://lemonergy.com/learn/glossary/acir/", "mentions": [ "impedance", "diffusion" ] } }, "edges": [ { "id": "edge:2655", "source": "term:acir", "target": "topic:topic-testing", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:2656", "source": "term:acir", "target": "term:dcir", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:2657", "source": "term:acir", "target": "term:internal-resistance", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:2658", "source": "term:acir", "target": "term:electrochemical-impedance-spectroscopy", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:2659", "source": "term:acir", "target": "term:end-of-line-testing", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/acir/impedance", "source": "term:acir", "target": "term:impedance", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:mentions/acir/diffusion", "source": "term:acir", "target": "term:diffusion", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:2662", "source": "term:acir", "target": "visual:impedance", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } } ], "neighbors": [ { "id": "topic:topic-testing", "type": "Topic", "label": "Testing methods", "properties": { "id": "topic-testing", "name": "Testing methods", "lede": "The measurements and test procedures that characterise a cell or pack, from capacity and pulse tests to abuse and environmental tests.", "context": "Record specimen, state, instrument, temperature and timing.", "example": "Resistance immediately after a current step can differ from a ten-second value because slower polarization contributes.", "lesson_url": "https://lemonergy.com/learn/fundamentals/capacity-and-c-rate/", "lesson_label": "Open capacity measurements" } }, { "id": "term:dcir", "type": "Term", "label": "DC internal resistance", "properties": { "id": "dcir", "name": "DC internal resistance", "abbr": "DCIR", "aka": [ "DC-IR", "pulse resistance" ], "section": "topic-testing", "definition": "Internal resistance measured from the voltage change during a current pulse of defined length, usually 10 s or 18 s. It is larger than the AC value because it includes charge-transfer and some diffusion, and it depends on SOC, temperature and pulse duration.", "unit": "mΩ", "related": [ "internal-resistance", "acir", "hppc", "impedance-rise" ], "url": "https://lemonergy.com/learn/glossary/dcir/", "mentions": [ "state-of-charge", "diffusion" ] } }, { "id": "term:internal-resistance", "type": "Term", "label": "Internal resistance", "properties": { "id": "internal-resistance", "name": "Internal resistance", "abbr": "IR", "aka": [ "DC resistance", "DCIR" ], "section": "topic-units", "definition": "The resistance a cell presents to current, from its foils, electrolyte, interfaces and the reactions themselves. It converts part of the delivered energy into heat, sets the voltage drop under load, and rises as the cell ages; a large automotive cell has about a milliohm, a small cylindrical cell tens.", "unit": "mΩ", "related": [ "ohms-law", "ir-drop", "impedance-rise", "dcir", "area-specific-resistance", "resistance-capacity-product" ], "lesson": "fundamentals/battery-basics/#datasheet", "url": "https://lemonergy.com/learn/glossary/internal-resistance/", "mentions": [ "electrolyte", "cylindrical-cell" ] } }, { "id": "term:electrochemical-impedance-spectroscopy", "type": "Term", "label": "Electrochemical impedance spectroscopy", "properties": { "id": "electrochemical-impedance-spectroscopy", "name": "Electrochemical impedance spectroscopy", "abbr": "EIS", "section": "topic-testing", "definition": "Measuring a cell’s impedance across a range of frequencies, from kilohertz to millihertz, with a small alternating signal. The spectrum separates ohmic, interface and diffusion processes by their time scale and is read on a Nyquist plot.", "related": [ "nyquist-plot", "impedance", "randles-circuit", "charge-transfer", "warburg-impedance" ], "url": "https://lemonergy.com/learn/glossary/electrochemical-impedance-spectroscopy/", "mentions": [ "diffusion" ] } }, { "id": "term:end-of-line-testing", "type": "Term", "label": "End-of-line testing", "properties": { "id": "end-of-line-testing", "name": "End-of-line testing", "abbr": "EOL test", "section": "topic-manufacturing", "definition": "The final measurements on every finished cell — capacity, internal resistance and open-circuit voltage — used to reject faulty cells and sort good ones into matched grades.", "related": [ "grading", "capacity-test", "k-value", "cell-finishing" ], "lesson": "fundamentals/cell-production/#finishing", "url": "https://lemonergy.com/learn/glossary/end-of-line-testing/", "mentions": [ "internal-resistance", "open-circuit-voltage" ] } }, { "id": "term:impedance", "type": "Term", "label": "Impedance", "properties": { "id": "impedance", "name": "Impedance", "abbr": "Z", "section": "topic-units", "definition": "The frequency-dependent generalisation of resistance, with a magnitude and a phase. A cell’s impedance separates ohmic, charge-transfer and diffusion contributions that a single DC resistance lumps together.", "unit": "Ω", "related": [ "internal-resistance", "electrochemical-impedance-spectroscopy", "nyquist-plot" ], "url": "https://lemonergy.com/learn/glossary/impedance/", "mentions": [ "diffusion" ] } }, { "id": "term:diffusion", "type": "Term", "label": "Diffusion", "properties": { "id": "diffusion", "name": "Diffusion", "section": "topic-transport", "definition": "The net movement of a species from where it is concentrated to where it is scarce, driven by random thermal motion. In a cell lithium diffuses through the electrolyte in the pores and, far more slowly, through the solid particles themselves.", "related": [ "ficks-first-law", "diffusion-coefficient", "solid-state-diffusion", "concentration-gradient", "migration" ], "lesson": "transport/ficks-first-law/#in-a-cell", "url": "https://lemonergy.com/learn/glossary/diffusion/", "mentions": [ "electrolyte" ] } }, { "id": "visual:impedance", "type": "Visual", "label": "Read an impedance semicircle", "properties": { "title": "Read an impedance semicircle", "summary": "A series resistance plus one parallel RC branch gives a single semicircle.", "readout": "High-frequency intercept: 10 mΩ. Arc width: 30 mΩ. Low-frequency intercept: 40 mΩ.", "formula": "Z = R₀ + R₁ / (1 + jωR₁C)", "note": "No diffusion tail or inductive loop. The plotted aspect ratio may distort the semicircle.", "software": { "status": "reference", "label": "Reference concept", "body": "An analytical R₀ + (R₁ ∥ C) example. Diffusion and inductance are omitted; this is neither a measured spectrum nor an identified cell model.", "href": "../chapter-1/" }, "html": "
R₀ + parallel RC impedance
R₀ + parallel RC impedanceReal impedance Z′ (mΩ) versus −Imaginary impedance −Z″ (mΩ). High frequency → low frequency. Interpretation follows the graphs.005.6311.311.322.516.933.822.545Real impedance Z′ (mΩ)−Imaginary impedance −Z″(mΩ)
High frequency → low frequency
" } } ] }