{ "node": { "id": "term:rate-capability", "type": "Term", "label": "Rate capability", "properties": { "id": "rate-capability", "name": "Rate capability", "section": "topic-ratings", "definition": "How much of its capacity a cell can still deliver as the C-rate rises. It is measured by discharging at a series of rates and falls faster for thick, dense electrodes and at low temperature.", "related": [ "c-rate", "ideal-duration", "polarization", "tortuosity", "peukert" ], "url": "https://lemonergy.com/learn/glossary/rate-capability/", "mentions": [] } }, "edges": [ { "id": "edge:960", "source": "term:rate-capability", "target": "topic:topic-ratings", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:961", "source": "term:rate-capability", "target": "term:c-rate", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:962", "source": "term:rate-capability", "target": "term:ideal-duration", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:963", "source": "term:rate-capability", "target": "term:polarization", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:964", "source": "term:rate-capability", "target": "term:tortuosity", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:965", "source": "term:rate-capability", "target": "term:peukert", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:966", "source": "term:rate-capability", "target": "visual:peukert", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } } ], "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: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.", "formula": "C-rate = I / Q_nominal", "unit": "h⁻¹", "related": [ "nominal-capacity", "ideal-duration", "current", "e-rate", "fast-charging" ], "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": [] } }, { "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:polarization", "type": "Term", "label": "Polarization", "properties": { "id": "polarization", "name": "Polarization", "aka": [ "overvoltage" ], "section": "topic-charging", "definition": "The gap between a cell’s terminal voltage under load and its open-circuit voltage. It has ohmic, charge-transfer and concentration parts, grows with current and falling temperature, and is where delivered energy is lost.", "unit": "V", "related": [ "overpotential", "ir-drop", "concentration-polarization", "open-circuit-voltage", "polarisation-curve" ], "url": "https://lemonergy.com/learn/glossary/polarization/", "mentions": [ "voltage", "closed-circuit-voltage" ] } }, { "id": "term:tortuosity", "type": "Term", "label": "Tortuosity", "properties": { "id": "tortuosity", "name": "Tortuosity", "abbr": "τ", "section": "topic-transport", "definition": "How winding the path through a porous layer is, compared with a straight line through it. High tortuosity means ions travel much further than the layer is thick, which limits how fast a thick, dense electrode can be charged or discharged.", "unit": "—", "related": [ "porosity", "bruggeman-relation", "porous-electrode", "rate-capability", "ionic-path" ], "lesson": "fundamentals/cell-architecture/#porosity", "url": "https://lemonergy.com/learn/glossary/tortuosity/", "mentions": [ "electrode", "winding" ] } }, { "id": "term:peukert", "type": "Term", "label": "Peukert’s law", "properties": { "id": "peukert", "name": "Peukert’s law", "section": "topic-ratings", "definition": "An empirical rule that delivered capacity falls as a power of the discharge current, with an exponent of 1.1–1.3 for lead–acid. For lithium-ion the exponent is close to 1, so the law is rarely used.", "formula": "t = H·(C/(I·H))^k", "related": [ "rate-capability", "lead-acid", "nominal-capacity" ], "example": { "title": "Compare ideal and Peukert durations", "text": "Consider a hypothetical lead-acid rating of 100 Ah at the 20 h rate, with k = 1.2. At 10 A, t = 20 × (100/(10 × 20))^1.2 gives about 8.7 h, rather than the ideal 10 h." }, "notes": [ "The exponent must be fitted to the battery and test conditions; do not transfer this example to lithium-ion cells." ], "url": "https://lemonergy.com/learn/glossary/peukert/", "mentions": [] } }, { "id": "visual:peukert", "type": "Visual", "label": "High current and usable capacity", "properties": { "title": "High current and usable capacity", "summary": "An empirical exponent changes the ideal inverse-current duration.", "readout": "At 5 A the ideal duration is 2 h; the chosen exponent gives 1.45 h (7.248 Ah delivered).", "formula": "t = H [C / (I H)]ᵏ", "note": "Not fitted cell data. A Ragone plot compares specific power and specific energy across measured or modeled conditions.", "software": { "status": "reference", "label": "Reference concept", "body": "This uses a 10 Ah rating at a 10-hour discharge. Peukert coefficients are empirical and chemistry-specific. ideal_duration_hours assumes ideal inverse-current behavior.", "href": "../fundamentals/capacity-and-c-rate/" }, "html": "
Empirical versus ideal duration
Empirical versus ideal durationDischarge current (A) versus Duration (h). Peukert example; Ideal 10 Ah / I. Interpretation follows the graphs.012.53.2555.57.57.751010Discharge current (A)Duration (h)
Peukert exampleIdeal 10 Ah / I (dashed)
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