{ "node": { "id": "term:c-rate", "type": "Term", "label": "C-rate", "properties": { "id": "c-rate", "name": "C-rate", "section": "topic-ratings", "definition": "Current divided by nominal capacity, in reciprocal hours. 1C on a 20 Ah cell is 20 A; 2C is 40 A. C-rate lets you compare loads on cells of different sizes. The C here is not the coulomb, whose symbol is also C.", "formula": "C-rate = I / Q_nominal", "unit": "h⁻¹", "related": [ "nominal-capacity", "ideal-duration", "current", "e-rate", "fast-charging", "standard-charge-current" ], "lesson": "fundamentals/capacity-and-c-rate/#c-rate", "example": { "title": "Convert a rating into amperes", "text": "For a 5 Ah cell, 0.5C means 2.5 A, 1C means 5 A and 2C means 10 A. Dividing 2.5 A by 5 Ah returns 0.5 h⁻¹, conventionally written 0.5C." }, "url": "https://lemonergy.com/learn/glossary/c-rate/", "mentions": [ "coulomb" ] } }, "edges": [ { "id": "edge:usedIn/term:c-rate/workflow:c-rate", "source": "term:c-rate", "target": "workflow:c-rate", "type": "usedIn", "properties": { "sourceFile": "wiki-blocks.json" } }, { "id": "edge:belongsTo/term:c-rate/topic:topic-ratings", "source": "term:c-rate", "target": "topic:topic-ratings", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:relatedTo/term:c-rate/term:nominal-capacity", "source": "term:c-rate", "target": "term:nominal-capacity", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:relatedTo/term:c-rate/term:ideal-duration", "source": "term:c-rate", "target": "term:ideal-duration", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:relatedTo/term:c-rate/term:current", "source": "term:c-rate", "target": "term:current", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:relatedTo/term:c-rate/term:e-rate", "source": "term:c-rate", "target": "term:e-rate", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:relatedTo/term:c-rate/term:fast-charging", "source": "term:c-rate", "target": "term:fast-charging", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:relatedTo/term:c-rate/term:standard-charge-current", "source": "term:c-rate", "target": "term:standard-charge-current", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/c-rate/coulomb", "source": "term:c-rate", "target": "term:coulomb", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:explainedIn/term:c-rate/lesson:fundamentals/capacity-and-c-rate/", "source": "term:c-rate", "target": "lesson:fundamentals/capacity-and-c-rate/", "type": "explainedIn", "properties": { "sourceFile": "terms.json", "url": "https://lemonergy.com/learn/fundamentals/capacity-and-c-rate/#c-rate" } }, { "id": "edge:illustratedBy/term:c-rate/visual:capacity", "source": "term:c-rate", "target": "visual:capacity", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } }, { "id": "edge:cites/term:c-rate/reference:sandia-performance", "source": "term:c-rate", "target": "reference:sandia-performance", "type": "cites", "properties": { "sourceFile": "wiki-references.json", "scope": "direct technical reference" } } ], "neighbors": [ { "id": "workflow:c-rate", "type": "Workflow", "label": "Convert C-rate into current", "properties": { "id": "c-rate", "title": "Convert C-rate into current", "kind": "core", "summary": "Lemonergy Core evaluates this relation.", "steps": [ "Open the lesson and inspect the equation.", "Change one input while holding the others fixed." ], "example": "A 5 Ah cell at 0.5C corresponds to 2.5 A. At 2C it corresponds to 10 A.", "observe": "Compare the result with the equation and units.", "limits": "Current magnitudes do not establish safe charge rates.", "url": "https://lemonergy.com/learn/fundamentals/capacity-and-c-rate/", "label": "Open the worked lesson", "evidence": [ "src/battery_core/capacity.py" ] } }, { "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:nominal-capacity", "type": "Term", "label": "Nominal capacity", "properties": { "id": "nominal-capacity", "name": "Nominal capacity", "aka": [ "rated capacity" ], "section": "topic-ratings", "definition": "The charge a cell is rated to deliver under specified test conditions — current, temperature, rest and voltage limits — usually in ampere-hours.", "unit": "Ah", "related": [ "ampere-hour", "c-rate", "capacity-test", "usable-capacity", "state-of-health" ], "lesson": "fundamentals/capacity-and-c-rate/#nominal-capacity", "url": "https://lemonergy.com/learn/glossary/nominal-capacity/", "mentions": [] } }, { "id": "term:ideal-duration", "type": "Term", "label": "Ideal duration", "properties": { "id": "ideal-duration", "name": "Ideal duration", "section": "topic-ratings", "definition": "t = 1 / C-rate: how long a constant current would take to transfer the full nominal capacity. A definition, not a prediction of real runtime.", "formula": "t = 1 / C-rate", "unit": "h", "related": [ "c-rate", "cutoff-voltage", "rate-capability" ], "lesson": "fundamentals/capacity-and-c-rate/#area", "example": { "title": "Estimate an ideal duration", "text": "At 0.5C, an ideal full-capacity constant-current discharge takes 1 / 0.5 = 2 h. A real discharge can end earlier at its voltage limit; CC-CV charging includes a taper and does not follow this duration alone." }, "url": "https://lemonergy.com/learn/glossary/ideal-duration/", "mentions": [ "nominal-capacity", "constant-current", "service-life" ] } }, { "id": "term:current", "type": "Term", "label": "Current", "properties": { "id": "current", "name": "Current", "section": "topic-units", "definition": "The rate at which charge flows through the cell and its circuit, in amperes. Outside the cell it is carried by electrons; inside, by lithium ions moving through the electrolyte.", "formula": "I = dQ/dt", "unit": "A", "related": [ "ampere", "c-rate", "ionic-path" ], "lesson": "fundamentals/cell-anatomy/#discharge", "example": { "title": "Convert charge transfer to current", "text": "If 120 C passes a point in 60 s at a steady rate, the current is 2 A. When the rate varies, integrate the current trace to recover the total charge." }, "url": "https://lemonergy.com/learn/glossary/current/", "mentions": [ "electrolyte" ] } }, { "id": "term:e-rate", "type": "Term", "label": "E-rate", "properties": { "id": "e-rate", "name": "E-rate", "aka": [ "P-rate" ], "section": "topic-ratings", "definition": "Power divided by nominal energy, the energy-based cousin of the C-rate: a 1E discharge empties a cell’s watt-hours in one hour. Grid-storage contracts are often written in E-rates or hours of discharge rather than in amperes. Cell datasheets write it as 1P or 0.5P: 1P on a 500 Wh cell is 500 W.", "formula": "E-rate = P / E_nominal", "unit": "h⁻¹", "related": [ "c-rate", "nominal-energy", "stationary-storage" ], "example": { "title": "Convert energy rating to power", "text": "A 20 kWh battery delivering 10 kW operates at 0.5 h⁻¹, conventionally 0.5E. At constant power with ideal full energy availability, the corresponding duration is 2 h." }, "url": "https://lemonergy.com/learn/glossary/e-rate/", "mentions": [] } }, { "id": "term:fast-charging", "type": "Term", "label": "Fast charging", "properties": { "id": "fast-charging", "name": "Fast charging", "section": "topic-charging", "definition": "Charging intended to replenish a specified amount of energy or state of charge in a short time. There is no universal C-rate threshold: performance depends on cell chemistry, temperature, starting state and power limits. High current can increase heating and lithium-plating risk, requiring appropriate limits.", "related": [ "lithium-plating", "c-rate", "cc-cv-charging", "dc-fast-charging", "thermal-management", "mscc" ], "url": "https://lemonergy.com/learn/glossary/fast-charging/", "mentions": [ "state-of-charge" ] } }, { "id": "term:standard-charge-current", "type": "Term", "label": "Standard charge current", "properties": { "id": "standard-charge-current", "name": "Standard charge current", "aka": [ "standard charge rate" ], "section": "topic-charging", "definition": "The charge current a manufacturer recommends for routine charging and uses in its rated tests, often 0.5C or 1C. It sits below the maximum charge current, which the cell tolerates but ages faster under, especially when cold.", "related": [ "c-rate", "cc-cv-charging", "fast-charging", "continuous-current", "datasheet" ], "url": "https://lemonergy.com/learn/glossary/standard-charge-current/", "mentions": [] } }, { "id": "term:coulomb", "type": "Term", "label": "Coulomb", "properties": { "id": "coulomb", "name": "Coulomb", "abbr": "C", "section": "topic-units", "definition": "The SI unit of electric charge; one ampere flowing for one second. Battery engineers prefer the ampere-hour, which is 3600 coulombs, because cells deliver their charge over hours.", "unit": "C", "related": [ "ampere-hour", "faradays-constant" ], "url": "https://lemonergy.com/learn/glossary/coulomb/", "mentions": [ "ampere", "electric-charge" ] } }, { "id": "lesson:fundamentals/capacity-and-c-rate/", "type": "Lesson", "label": "Lesson 2 · Capacity and C-rate", "properties": { "url": "https://lemonergy.com/learn/fundamentals/capacity-and-c-rate/" } }, { "id": "visual:capacity", "type": "Visual", "label": "C-rate, current and duration", "properties": { "title": "C-rate, current and duration", "summary": "A C-rate becomes an actual current only when capacity is known.", "readout": "5 Ah × 1C = 5 A. Ideal duration: 1 h (60 min).", "formula": "I = Q × C-rate; t_ideal = 1 / C-rate", "note": "Voltage cutoff, losses, temperature and rate-dependent capacity are excluded.", "software": { "status": "implemented", "label": "Implemented in battery-core", "body": "current_from_c_rate calculates I = Q × C-rate; ideal_duration_hours calculates 1 / C-rate. Neither predicts voltage-cutoff time or real usable capacity.", "href": "../fundamentals/capacity-and-c-rate/" }, "html": "
Ideal remaining charge
Ideal remaining chargeTime (h) versus Remaining charge (Ah). 1C. Interpretation follows the graphs.001.2512.523.75354Time (h)Remaining charge (Ah)
1C
" } }, { "id": "reference:sandia-performance", "type": "Reference", "label": "DOE Energy Storage Handbook, Chapter 16: Energy Storage Performance Testing", "properties": { "title": "DOE Energy Storage Handbook, Chapter 16: Energy Storage Performance Testing", "publisher": "Sandia National Laboratories", "url": "https://www.sandia.gov/app/uploads/sites/163/2021/09/ESHB_Ch16_Testing_Rosewater.pdf", "type": "Technical handbook chapter", "scope": "Section 2.1.2.1 explains capacity, C-rate and the distinction between capacity and energy; also covers pulse characterization.", "accessed": "2026-10-27" } } ] }