{ "node": { "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": [] } }, "edges": [ { "id": "edge:967", "source": "term:peukert", "target": "topic:topic-ratings", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:968", "source": "term:peukert", "target": "term:rate-capability", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:969", "source": "term:peukert", "target": "term:lead-acid", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:970", "source": "term:peukert", "target": "term:nominal-capacity", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:971", "source": "term:peukert", "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: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": [] } }, { "id": "term:lead-acid", "type": "Term", "label": "Lead–acid battery", "properties": { "id": "lead-acid", "name": "Lead–acid battery", "section": "topic-other-chemistries", "definition": "The oldest rechargeable chemistry, lead and lead dioxide electrodes in sulfuric acid, at 2 V per cell. Heavy and short-lived in deep cycling but cheap, recyclable and good at cold cranking, it still starts most cars and backs up most telecom sites.", "related": [ "nominal-voltage", "recycling", "specific-energy" ], "lesson": "labs/battery-materials-lab/#bml-market", "url": "https://lemonergy.com/learn/glossary/lead-acid/", "mentions": [] } }, { "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": "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)
" } } ] }