{ "node": { "id": "term:voltage", "type": "Term", "label": "Voltage", "properties": { "id": "voltage", "name": "Voltage", "aka": [ "terminal voltage" ], "section": "topic-units", "definition": "The potential difference between a cell’s two terminals. It comes from the chemical difference between the electrodes, moves with state of charge, and sags under load because of internal resistance.", "unit": "V", "related": [ "open-circuit-voltage", "nominal-voltage", "internal-resistance", "ir-drop" ], "lesson": "fundamentals/cell-anatomy/#voltage", "url": "https://lemonergy.com/learn/glossary/voltage/", "mentions": [ "state-of-charge" ] } }, "edges": [ { "id": "edge:157", "source": "term:voltage", "target": "workflow:ohm-circuit", "type": "usedIn", "properties": { "sourceFile": "wiki-blocks.json" } }, { "id": "edge:191", "source": "term:voltage", "target": "topic:topic-units", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:192", "source": "term:voltage", "target": "term:open-circuit-voltage", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:193", "source": "term:voltage", "target": "term:nominal-voltage", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:194", "source": "term:voltage", "target": "term:internal-resistance", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:195", "source": "term:voltage", "target": "term:ir-drop", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/voltage/state-of-charge", "source": "term:voltage", "target": "term:state-of-charge", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:197", "source": "term:voltage", "target": "lesson:fundamentals/cell-anatomy/", "type": "explainedIn", "properties": { "sourceFile": "terms.json", "url": "https://lemonergy.com/learn/fundamentals/cell-anatomy/#voltage" } }, { "id": "edge:198", "source": "term:voltage", "target": "visual:voltage", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } }, { "id": "edge:199", "source": "term:voltage", "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:open-circuit-voltage", "type": "Term", "label": "Open-circuit voltage", "properties": { "id": "open-circuit-voltage", "name": "Open-circuit voltage", "abbr": "OCV", "section": "topic-state", "definition": "The voltage across a cell’s terminals when no current flows and the cell has rested long enough for the voltage to settle. 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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:ir-drop", "type": "Term", "label": "IR drop", "properties": { "id": "ir-drop", "name": "IR drop", "aka": [ "ohmic drop", "voltage sag" ], "section": "topic-charging", "definition": "The instant step in terminal voltage when current starts or stops, equal to current times internal resistance. It is lost as heat and is the reason a cell’s voltage under load sits below its open-circuit voltage.", "formula": "ΔV = I × R", "unit": "V", "related": [ "internal-resistance", "ohms-law", "polarization", "open-circuit-voltage" ], "example": { "title": "Distinguish a current step from SOC change", "text": "When discharge current jumps from 0 A to 10 A through an illustrative 20 mΩ resistance, terminal voltage immediately drops by 0.2 V. Slower polarization and SOC change are separate effects." }, "url": "https://lemonergy.com/learn/glossary/ir-drop/", "mentions": [ "voltage", "closed-circuit-voltage" ] } }, { "id": "term:state-of-charge", "type": "Term", "label": "State of charge", "properties": { "id": "state-of-charge", "name": "State of charge", "abbr": "SOC", "section": "topic-state", "definition": "How full a cell is, as a fraction of its available capacity. State of charge, like temperature, affects how fast a stored cell ages.", "unit": "%", "related": [ "depth-of-discharge", "ocv-soc-curve", "coulomb-counting", "state-of-health", "bms" ], "lesson": "fundamentals/battery-aging/#storage-soc", "example": { "title": "Interpret a charge inventory", "text": "If available capacity is 5 Ah and 3 Ah remains by the chosen estimator, SOC is 60%. A different estimate of available capacity changes this percentage, so compare SOC values only with the capacity convention recorded." }, "url": "https://lemonergy.com/learn/glossary/state-of-charge/", "mentions": [ "usable-capacity" ] } }, { "id": "lesson:fundamentals/cell-anatomy/", "type": "Lesson", "label": "Lesson 1 · Cell anatomy", "properties": { "url": "https://lemonergy.com/learn/fundamentals/cell-anatomy/" } }, { "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" } } ] }