{ "node": { "id": "term:watt", "type": "Term", "label": "Watt", "properties": { "id": "watt", "name": "Watt", "abbr": "W", "section": "topic-units", "definition": "The SI unit of power: one joule per second, or in a circuit, volts times amperes. A cell delivering 20 A at 3.6 V is supplying 72 W.", "formula": "P = V × I", "unit": "W", "related": [ "power", "watt-hour", "specific-power" ], "example": { "title": "Calculate electrical power", "text": "At a particular instant, a terminal voltage of 12 V and current magnitude of 3 A correspond to 36 W. State whether the battery is receiving or supplying that power." }, "url": "https://lemonergy.com/learn/glossary/watt/", "mentions": [ "joule" ] } }, "edges": [ { "id": "edge:57", "source": "term:watt", "target": "workflow:loss-accounting", "type": "usedIn", "properties": { "sourceFile": "wiki-blocks.json" } }, { "id": "edge:222", "source": "term:watt", "target": "topic:topic-units", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:223", "source": "term:watt", "target": "term:power", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:224", "source": "term:watt", "target": "term:watt-hour", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:225", "source": "term:watt", "target": "term:specific-power", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/watt/joule", "source": "term:watt", "target": "term:joule", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:227", "source": "term:watt", "target": "visual:energy", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } }, { "id": "edge:228", "source": "term:watt", "target": "reference:bipm-si", "type": "cites", "properties": { "sourceFile": "wiki-references.json", "scope": "direct technical reference" } } ], "neighbors": [ { "id": "workflow:loss-accounting", "type": "Workflow", "label": "Compare grid and battery energy", "properties": { "id": "loss-accounting", "title": "Compare grid and battery energy", "kind": "studio", "summary": "Separate energy and loss signals make efficiency visible.", "steps": [ "Keep battery settings fixed.", "Change converter efficiency." ], "example": "7 kW battery-side power at 95% efficiency requires about 7.37 kW grid power and produces about 0.37 kW converter loss.", "observe": "Battery I²R loss differs from converter loss.", "limits": "A loss signal is not a predicted temperature. This network takes external temperature.", "url": "https://design.lemonergy.com/cosim.html?example=charging-home", "label": "Open the Studio example", "evidence": [ "js/charging-control.js", "js/charging-scenarios.js", "docs/CHARGING_BLOCKS_SPEC.md" ] } }, { "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:power", "type": "Term", "label": "Power", "properties": { "id": "power", "name": "Power", "section": "topic-units", "definition": "The rate at which a cell delivers or absorbs energy: voltage times current, in watts. Power is limited by internal resistance and temperature long before capacity runs out.", "formula": "P = V × I", "unit": "W", "related": [ "watt", "specific-power", "state-of-power", "internal-resistance" ], "example": { "title": "Separate power from energy", "text": "A 100 W load running for 30 min uses 50 Wh. Power tells you how fast energy is transferred; the duration determines how much energy is transferred." }, "url": "https://lemonergy.com/learn/glossary/power/", "mentions": [] } }, { "id": "term:watt-hour", "type": "Term", "label": "Watt-hour", "properties": { "id": "watt-hour", "name": "Watt-hour", "abbr": "Wh", "section": "topic-units", "definition": "A unit of energy: one watt for one hour, or 3600 joules. A cell’s nominal energy in watt-hours is its capacity in ampere-hours times its nominal voltage — 20 Ah at 3.65 V is 73 Wh.", "formula": "E = Q × V", "unit": "Wh", "related": [ "nominal-energy", "kilowatt-hour", "ampere-hour", "nominal-voltage" ], "lesson": "fundamentals/capacity-and-c-rate/#energy", "example": { "title": "Compare a Wh rating with Ah", "text": "A nominal 3.6 V, 5 Ah cell is rated at approximately 18 Wh. Watt-hours measure energy, while ampere-hours measure charge; the voltage is needed to convert between them." }, "url": "https://lemonergy.com/learn/glossary/watt-hour/", "mentions": [ "watt" ] } }, { "id": "term:specific-power", "type": "Term", "label": "Specific power", "properties": { "id": "specific-power", "name": "Specific power", "aka": [ "power density" ], "section": "topic-ratings", "definition": "Deliverable power per unit mass, in watts per kilogram; power density is the same per litre. A cell is designed for energy or for power, rarely both: thin electrodes give power, thick ones give energy.", "unit": "W/kg", "related": [ "power", "specific-energy", "ragone-plot", "areal-loading", "power-cell-energy-cell" ], "url": "https://lemonergy.com/learn/glossary/specific-power/", "mentions": [] } }, { "id": "term:joule", "type": "Term", "label": "Joule", "properties": { "id": "joule", "name": "Joule", "abbr": "J", "section": "topic-units", "definition": "The SI unit of energy; one watt for one second. Battery energy is almost always quoted in watt-hours instead, and 1 Wh equals 3600 J.", "unit": "J", "related": [ "watt-hour", "energy" ], "url": "https://lemonergy.com/learn/glossary/joule/", "mentions": [ "watt" ] } }, { "id": "visual:energy", "type": "Visual", "label": "From charge to energy", "properties": { "title": "From charge to energy", "summary": "Voltage connects capacity in ampere-hours to nominal energy in watt-hours.", "readout": "5 Ah × 12 V = 60 Wh nominal energy.", "formula": "E_nominal = Q_nominal V_nominal; actual energy = ∫ VI dt", "note": "Specific energy divides energy by mass; energy density divides it by volume.", "software": { "status": "implemented", "label": "Implemented in battery-core", "body": "nominal_energy_wh multiplies nominal voltage by capacity. Actual discharge energy requires the integral of voltage × current.", "href": "../fundamentals/capacity-and-c-rate/" }, "html": "
Nominal energy versus capacity
Nominal energy versus capacityCapacity (Ah) versus Energy (Wh). 12 V rating. Interpretation follows the graphs.00605120101801524020Capacity (Ah)Energy (Wh)
12 V rating
" } }, { "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" } } ] }