{ "node": { "id": "term:ohm", "type": "Term", "label": "Ohm", "properties": { "id": "ohm", "name": "Ohm", "abbr": "Ω", "section": "topic-units", "definition": "The SI unit of electrical resistance: one volt per ampere. Cell internal resistance is about a milliohm for a large automotive cell and tens of milliohms for a small cylindrical one.", "unit": "Ω", "related": [ "internal-resistance", "ohms-law", "impedance" ], "url": "https://lemonergy.com/learn/glossary/ohm/", "mentions": [ "ampere", "volt" ] } }, "edges": [ { "id": "edge:155", "source": "term:ohm", "target": "workflow:ohm-circuit", "type": "usedIn", "properties": { "sourceFile": "wiki-blocks.json" } }, { "id": "edge:265", "source": "term:ohm", "target": "topic:topic-units", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:266", "source": "term:ohm", "target": "term:internal-resistance", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:267", "source": "term:ohm", "target": "term:ohms-law", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:268", "source": "term:ohm", "target": "term:impedance", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/ohm/ampere", "source": "term:ohm", "target": "term:ampere", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:mentions/ohm/volt", "source": "term:ohm", "target": "term:volt", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:271", "source": "term:ohm", "target": "visual:voltage", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } }, { "id": "edge:272", "source": "term:ohm", "target": "reference:bipm-si", "type": "cites", "properties": { "sourceFile": "wiki-references.json", "scope": "direct technical reference" } } ], "neighbors": [ { "id": "workflow:ohm-circuit", "type": "Workflow", "label": "Relate current and voltage", "properties": { "id": "ohm-circuit", "title": "Relate current and voltage", "kind": "studio", "summary": "Conserving components solve constitutive relations and node balance.", "steps": [ "Inspect source and resistor in the RC example.", "Compare branch current with resistor voltage." ], "example": "A 1 V drop across 2 Ω implies 0.5 A.", "observe": "Topology sets individual element voltages.", "limits": "The RC example includes a capacitor: transient current varies and source voltage is not always resistor voltage.", "url": "https://design.lemonergy.com/cosim.html?example=physical-rc", "label": "Open the electrical circuit", "evidence": [ "js/physical-network.js", "js/studio-examples.js" ] } }, { "id": "topic:topic-units", "type": "Topic", "label": "Units and electrical basics", "properties": { "id": "topic-units", "name": "Units and electrical basics", "lede": "The quantities every datasheet is written in, and how they relate.", "context": "Use consistent units and cell/pack basis.", "example": "10 A for 30 min transfers 5 Ah. At constant 3.6 V this is 18 Wh; varying voltage requires integration.", "lesson_url": "https://lemonergy.com/learn/fundamentals/capacity-and-c-rate/", "lesson_label": "Open capacity and C-rate" } }, { "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:ohms-law", "type": "Term", "label": "Ohm’s law", "properties": { "id": "ohms-law", "name": "Ohm’s law", "section": "topic-units", "definition": "Voltage across a resistance equals current times that resistance. Applied to a cell it predicts the voltage drop under load from the internal resistance, which is the first-order reason terminal voltage sags.", "formula": "V = I × R", "related": [ "internal-resistance", "ir-drop", "ohm", "kirchhoffs-laws" ], "example": { "title": "Convert a resistance into a voltage drop", "text": "A 10 A current through a 20 mΩ resistance produces 0.2 V of voltage drop. Use 0.020 Ω in V = IR; inserting the number 20 without converting milliohms would be wrong." }, "url": "https://lemonergy.com/learn/glossary/ohms-law/", "mentions": [ "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:ampere", "type": "Term", "label": "Ampere", "properties": { "id": "ampere", "name": "Ampere", "abbr": "A", "section": "topic-units", "definition": "The SI unit of electric current: one coulomb of charge passing a point per second. Cell currents are quoted in amperes, or as a C-rate so cells of different size can be compared.", "unit": "A", "related": [ "coulomb", "c-rate", "current" ], "url": "https://lemonergy.com/learn/glossary/ampere/", "mentions": [] } }, { "id": "term:volt", "type": "Term", "label": "Volt", "properties": { "id": "volt", "name": "Volt", "abbr": "V", "section": "topic-units", "definition": "The SI unit of electric potential difference: one joule of energy per coulomb of charge. A lithium-ion cell sits around 3–4 V; packs reach hundreds of volts by putting cells in series.", "unit": "V", "related": [ "voltage", "nominal-voltage", "series-parallel" ], "url": "https://lemonergy.com/learn/glossary/volt/", "mentions": [ "coulomb", "joule" ] } }, { "id": "visual:voltage", "type": "Visual", "label": "Voltage under load", "properties": { "title": "Voltage under load", "summary": "Discharge current creates an ohmic drop below open-circuit voltage.", "readout": "5 A through 20 mΩ gives 0.1 V ohmic drop.", "formula": "V_terminal = OCV − I_discharge R", "note": "Chosen OCV curve; no chemistry calibration, hysteresis or voltage cutoff.", "software": { "status": "studio", "label": "Voltage relationship in Studio", "body": "The native battery calculates terminal voltage from OCV and resistance. The curve here is an illustrative OCV relationship, not a fitted cell dataset.", "href": "https://design.lemonergy.com/cosim.html?example=charging-home" }, "html": "
Illustrative OCV and loaded voltage
Illustrative OCV and loaded voltageSOC (%) versus Voltage (V). Open circuit; Under load. Interpretation follows the graphs.1.802.42253.05503.67754.3100SOC (%)Voltage (V)
Open circuitUnder load (dashed)
" } }, { "id": "reference:bipm-si", "type": "Reference", "label": "The International System of Units (SI), 9th edition", "properties": { "title": "The International System of Units (SI), 9th edition", "publisher": "Bureau International des Poids et Mesures", "url": "https://doi.org/10.59161/AUEZ1291", "type": "Metrology reference", "scope": "Definitions of SI units and coherent derived units; 2026 revision.", "year": 2026, "accessed": "2026-10-27" } } ] }