{ "node": { "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": [] } }, "edges": [ { "id": "edge:947", "source": "term:specific-power", "target": "topic:topic-ratings", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:948", "source": "term:specific-power", "target": "term:power", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:949", "source": "term:specific-power", "target": "term:specific-energy", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:950", "source": "term:specific-power", "target": "term:ragone-plot", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:951", "source": "term:specific-power", "target": "term:areal-loading", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:952", "source": "term:specific-power", "target": "term:power-cell-energy-cell", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:953", "source": "term:specific-power", "target": "visual:ragone", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } }, { "id": "edge:954", "source": "term:specific-power", "target": "reference:inl-ev-tests", "type": "cites", "properties": { "sourceFile": "wiki-references.json", "scope": "direct technical reference" } } ], "neighbors": [ { "id": "topic:topic-ratings", "type": "Topic", "label": "Capacity, energy, power and ratings", "properties": { "id": "topic-ratings", "name": "Capacity, energy, power and ratings", "lede": "The numbers that size a cell and let two cells be compared.", "context": "Separate nameplate ratings from test results.", "example": "5 Ah at 3.6 V gives 18 Wh nominally. Integrated measured terminal power may give a different result.", "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:specific-energy", "type": "Term", "label": "Specific energy", "properties": { "id": "specific-energy", "name": "Specific energy", "aka": [ "gravimetric energy density" ], "section": "topic-ratings", "definition": "Stored energy per unit mass, in watt-hours per kilogram. Commercial lithium-ion cells range from about 160 Wh/kg for LFP to around 270 Wh/kg for high-nickel chemistries; at pack level the figure drops by a quarter or more.", "unit": "Wh/kg", "related": [ "energy-density", "cell-to-pack-ratio", "specific-capacity", "ragone-plot" ], "lesson": "fundamentals/capacity-and-c-rate/#energy", "url": "https://lemonergy.com/learn/glossary/specific-energy/", "mentions": [] } }, { "id": "term:ragone-plot", "type": "Term", "label": "Ragone plot", "properties": { "id": "ragone-plot", "name": "Ragone plot", "section": "topic-ratings", "definition": "A log–log chart of specific power against specific energy on which each storage technology occupies a region. Capacitors sit high and left, batteries lower and right, and a single cell traces a curve as it is discharged faster.", "related": [ "specific-energy", "specific-power", "rate-capability" ], "url": "https://lemonergy.com/learn/glossary/ragone-plot/", "mentions": [] } }, { "id": "term:areal-loading", "type": "Term", "label": "Areal loading", "properties": { "id": "areal-loading", "name": "Areal loading", "aka": [ "mass loading", "areal capacity" ], "section": "topic-components", "definition": "How much active material, or capacity, an electrode carries per square centimetre of foil, typically 2–5 mAh/cm². Higher loading raises energy density but lengthens the ion path, which limits fast charging.", "unit": "mAh/cm², mg/cm²", "related": [ "coating", "energy-density", "fast-charging", "tortuosity" ], "example": { "title": "Convert mass and area", "text": "200 mg active material over 20 cm² gives 10 mg/cm² loading. State whether the measurement includes one or both coated sides." }, "url": "https://lemonergy.com/learn/glossary/areal-loading/", "mentions": [ "milliampere-hour", "electrode", "active-material" ] } }, { "id": "term:power-cell-energy-cell", "type": "Term", "label": "Power cell and energy cell", "properties": { "id": "power-cell-energy-cell", "name": "Power cell and energy cell", "section": "topic-applications", "definition": "Two design points of the same chemistry: a power cell has thin, porous electrodes and many tabs for high current and fast charging; an energy cell has thick, dense electrodes for maximum watt-hours. A hybrid car wants the first, a long-range car the second.", "related": [ "specific-power", "specific-energy", "areal-loading", "cell-design" ], "url": "https://lemonergy.com/learn/glossary/power-cell-energy-cell/", "mentions": [ "fast-charging" ] } }, { "id": "visual:ragone", "type": "Visual", "label": "Specific power versus specific energy", "properties": { "title": "Specific power versus specific energy", "summary": "A Ragone chart uses logarithmic axes to compare energy and power per unit mass.", "readout": "The chosen example is 10 Ah at a 10-hour rating, 3.7 V constant voltage and 0.1 kg mass. At higher current, power rises while usable specific energy falls when the exponent exceeds 1.", "formula": "Specific power = VI / mass; specific energy = VIt / mass", "note": "An illustrative cell curve, not technology-region data or a fitted lithium-ion result. The empirical exponent controls the rate effect.", "software": { "status": "reference", "label": "Reference concept", "body": "The curve is generated from an explicit empirical discharge assumption, not measured technology data. The core nominal-energy function does not predict this power-energy trade-off.", "href": "../fundamentals/capacity-and-c-rate/" }, "html": "
Illustrative power–energy trade-off
Illustrative power–energy trade-offSpecific energy (Wh/kg), log scale versus Specific power (W/kg), log scale. Increasing discharge current. Interpretation follows the graphs.1010031.61781003163165621,0001,000Specific energy (Wh/kg), logscaleSpecific power (W/kg),log scale
Increasing discharge current
" } }, { "id": "reference:inl-ev-tests", "type": "Reference", "label": "Battery Test Manual For Electric Vehicles, Revision 3", "properties": { "title": "Battery Test Manual For Electric Vehicles, Revision 3", "publisher": "Idaho National Laboratory", "url": "https://inldigitallibrary.inl.gov/sites/sti/sti/6492291.pdf", "type": "Test manual", "scope": "Performance characterization, pulse resistance/power, life testing and reference performance tests; historical 2015 edition.", "year": 2015, "authors": [ "Jon P. Christopherson" ], "accessed": "2026-10-27" } } ] }