{ "node": { "id": "term:adiabatic-isothermal", "type": "Term", "label": "Adiabatic and isothermal conditions", "properties": { "id": "adiabatic-isothermal", "name": "Adiabatic and isothermal conditions", "aka": [ "adiabatic", "isothermal" ], "section": "topic-thermal", "definition": "Two idealised thermal boundaries used in testing. Adiabatic means no heat escapes, so every joule raises the sample’s temperature — the principle of accelerating rate calorimetry and the worst case for a pack whose cooling fails. Isothermal means the sample is held at constant temperature while the heat it releases is measured, as in isothermal calorimetry.", "related": [ "accelerating-rate-calorimetry", "heat-generation", "thermal-characterisation", "thermal-runaway" ], "url": "https://lemonergy.com/learn/glossary/adiabatic-isothermal/", "mentions": [ "joule", "isothermal-calorimetry" ] } }, "edges": [ { "id": "edge:4641", "source": "term:adiabatic-isothermal", "target": "topic:topic-thermal", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:4642", "source": "term:adiabatic-isothermal", "target": "term:accelerating-rate-calorimetry", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:4643", "source": "term:adiabatic-isothermal", "target": "term:heat-generation", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:4644", "source": "term:adiabatic-isothermal", "target": "term:thermal-characterisation", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:4645", "source": "term:adiabatic-isothermal", "target": "term:thermal-runaway", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/adiabatic-isothermal/joule", "source": "term:adiabatic-isothermal", "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:mentions/adiabatic-isothermal/isothermal-calorimetry", "source": "term:adiabatic-isothermal", "target": "term:isothermal-calorimetry", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:4648", "source": "term:adiabatic-isothermal", "target": "visual:thermal", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } } ], "neighbors": [ { "id": "topic:topic-thermal", "type": "Topic", "label": "Thermal management and heat transfer", "properties": { "id": "topic-thermal", "name": "Thermal management and heat transfer", "lede": "How heat is made, moved and removed in cells and packs, and the hardware that keeps a battery at the right temperature.", "context": "Select spatial detail for the question.", "example": "Equal total heat in different layouts can produce different gradients. Average temperature can miss a hot spot.", "lesson_url": "https://lemonergy.com/learn/fundamentals/battery-aging/", "lesson_label": "Open temperature and aging" } }, { "id": "term:accelerating-rate-calorimetry", "type": "Term", "label": "Accelerating rate calorimetry", "properties": { "id": "accelerating-rate-calorimetry", "name": "Accelerating rate calorimetry", "abbr": "ARC", "section": "topic-safety", "definition": "A test in which a cell sits in an adiabatic chamber that follows its temperature, so any self-heating is not lost to the surroundings. It measures the onset temperature, the self-heating rate and the temperature at which runaway becomes unstoppable.", "related": [ "onset-temperature", "thermal-runaway", "differential-scanning-calorimetry" ], "url": "https://lemonergy.com/learn/glossary/accelerating-rate-calorimetry/", "mentions": [ "adiabatic-isothermal" ] } }, { "id": "term:heat-generation", "type": "Term", "label": "Heat generation", "properties": { "id": "heat-generation", "name": "Heat generation", "aka": [ "Bernardi equation" ], "section": "topic-thermal", "definition": "The heat a cell produces in operation: an irreversible part equal to current times overpotential, and a reversible part from the entropy change, I·T·dE/dT. The Bernardi equation sums them and feeds every thermal model.", "formula": "q = I(V − E_OCV) + I·T·(dE/dT)", "unit": "W", "related": [ "entropy-coefficient", "internal-resistance", "thermal-model", "thermal-management", "exothermic" ], "example": { "title": "Keep reversible and irreversible heat separate", "text": "With charging current +5 A and terminal voltage 0.10 V above OCV, the irreversible term is 0.50 W. At 300 K with dE/dT = +0.1 mV/K, the reversible contribution is +0.15 W, giving 0.65 W under this sign convention." }, "url": "https://lemonergy.com/learn/glossary/heat-generation/", "mentions": [ "overpotential" ] } }, { "id": "term:thermal-characterisation", "type": "Term", "label": "Thermal characterisation", "properties": { "id": "thermal-characterisation", "name": "Thermal characterisation", "aka": [ "heat capacity test", "entropy test" ], "section": "topic-testing", "definition": "Measuring the thermal properties a model needs: specific heat capacity in a calorimeter, thermal conductivity through and along the layers, the entropy coefficient from OCV against temperature, and heat generation under load. Without them a thermal model is a guess.", "related": [ "heat-generation", "entropy-coefficient", "thermal-model", "accelerating-rate-calorimetry" ], "url": "https://lemonergy.com/learn/glossary/thermal-characterisation/", "mentions": [ "open-circuit-voltage", "thermal-conductivity", "specific-heat-capacity" ] } }, { "id": "term:thermal-runaway", "type": "Term", "label": "Thermal runaway", "properties": { "id": "thermal-runaway", "name": "Thermal runaway", "section": "topic-safety", "definition": "Self-accelerating heating in a cell: heat speeds up reactions that release more heat, until the cell vents, catches fire or ruptures. An internal short, overcharge or external heating can trigger it.", "related": [ "onset-temperature", "thermal-propagation", "venting", "separator-shutdown", "thermal-runaway-energy", "exothermic" ], "lesson": "fundamentals/cell-anatomy/#short-circuit", "url": "https://lemonergy.com/learn/glossary/thermal-runaway/", "mentions": [ "overcharge" ] } }, { "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": "term:isothermal-calorimetry", "type": "Term", "label": "Isothermal calorimetry", "properties": { "id": "isothermal-calorimetry", "name": "Isothermal calorimetry", "aka": [ "isothermal microcalorimetry", "IMC", "heat-flow calorimetry" ], "section": "topic-testing", "definition": "Holding a cell at constant temperature inside a calorimeter and measuring the heat it gives off, down to microwatts, while it cycles or rests. It separates reversible entropic heat from irreversible losses and reveals the parasitic heat of slow side reactions, a quick indicator of how long a cell will last.", "related": [ "heat-generation", "entropy-coefficient", "thermal-characterisation", "accelerating-rate-calorimetry", "ultra-high-precision-coulometry" ], "url": "https://lemonergy.com/learn/glossary/isothermal-calorimetry/", "mentions": [] } }, { "id": "visual:thermal", "type": "Visual", "label": "Heat approaches an equilibrium", "properties": { "title": "Heat approaches an equilibrium", "summary": "Thermal resistance sets the steady temperature rise; thermal mass sets the response time.", "readout": "Steady rise: 10 K. Time constant: 8.333 min.", "formula": "ΔT = P R_th [1 − exp(−t / (C_th R_th))]", "note": "C_th = 500 J/K, fixed ambient and heat input, uniform temperature.", "software": { "status": "reference", "label": "Reference concept", "body": "Analysis → Charge session supports optional lumped thermal behavior. This independent explanation uses a 500 J/K thermal mass and constant heat input; it is not an application simulation result.", "href": "https://design.lemonergy.com/" }, "html": "
Temperature above ambient
Temperature above ambientTime (min) versus Temperature rise (K). Lumped response. Interpretation follows the graphs.001515303045456060Time (min)Temperature rise (K)
Lumped response
" } } ] }