{ "node": { "id": "term:thermal-resistance", "type": "Term", "label": "Thermal resistance", "properties": { "id": "thermal-resistance", "name": "Thermal resistance", "section": "topic-thermal", "definition": "The temperature difference needed to drive one watt of heat along a path, in kelvin per watt. A 1 mm layer of gap filler at 3 W/(m·K) over 100 cm² has about 0.03 K/W, so 30 W through it costs 1 K. Resistances in series add like electrical ones, which is how cell-to-coolant paths are budgeted.", "formula": "R_th = ΔT / Q = L / (k·A)", "unit": "K/W", "related": [ "thermal-conductivity", "thermal-interface-material", "cooling-plate", "heat-flux", "thermal-model" ], "example": { "title": "Translate heat into a temperature difference", "text": "A 2 K/W thermal path carrying a steady 5 W heat flow has a 10 K temperature difference across it. The temperature at the cold boundary is needed to obtain an absolute hot-side temperature." }, "url": "https://lemonergy.com/learn/glossary/thermal-resistance/", "mentions": [ "watt" ] } }, "edges": [ { "id": "edge:111", "source": "term:thermal-resistance", "target": "workflow:charge-thermal", "type": "usedIn", "properties": { "sourceFile": "wiki-blocks.json" } }, { "id": "edge:4563", "source": "term:thermal-resistance", "target": "topic:topic-thermal", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:4564", "source": "term:thermal-resistance", "target": "term:thermal-conductivity", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:4565", "source": "term:thermal-resistance", "target": "term:thermal-interface-material", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:4566", "source": "term:thermal-resistance", "target": "term:cooling-plate", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:4567", "source": "term:thermal-resistance", "target": "term:heat-flux", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:4568", "source": "term:thermal-resistance", "target": "term:thermal-model", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/thermal-resistance/watt", "source": "term:thermal-resistance", "target": "term:watt", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:4570", "source": "term:thermal-resistance", "target": "visual:thermal", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } }, { "id": "edge:4571", "source": "term:thermal-resistance", "target": "reference:openstax-heat", "type": "cites", "properties": { "sourceFile": "wiki-references.json", "scope": "direct technical reference" } } ], "neighbors": [ { "id": "workflow:charge-thermal", "type": "Workflow", "label": "Inspect pack temperature", "properties": { "id": "charge-thermal", "title": "Inspect pack temperature", "kind": "protocol", "summary": "The separate Charge session can include a lumped thermal node.", "steps": [ "Provide thermal mass and conductance.", "Compare two ambient temperatures." ], "example": "100 kJ/K thermal mass and 100 W/K conductance give a 1000 s no-source temperature-difference time constant.", "observe": "Temperature limits can pause charge; heater and mass are separate.", "limits": "One node does not resolve gradients, coolant geometry or runaway. Studio’s native charger instead uses external temperature.", "url": "https://design.lemonergy.com/", "label": "Open Design → Charge session", "evidence": [ "js/charger.js" ] } }, { "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:thermal-conductivity", "type": "Term", "label": "Thermal conductivity", "properties": { "id": "thermal-conductivity", "name": "Thermal conductivity", "abbr": "k", "aka": [ "λ", "through-plane conductivity", "in-plane conductivity" ], "section": "topic-thermal", "definition": "How readily a material conducts heat: the heat flux per unit temperature gradient. Cells are strongly anisotropic — around 25–45 W/(m·K) in-plane, along the metal foils, but below 1 W/(m·K) through-plane, across separators and coatings — so the side a cell is cooled from decides how hot its core runs.", "formula": "q″ = −k·dT/dx", "unit": "W/(m·K)", "related": [ "thermal-resistance", "thermal-diffusivity", "thermal-characterisation", "thermal-interface-material", "biot-number", "thermal-model" ], "example": { "title": "Calculate a slab heat flow", "text": "An illustrative 2 mm layer with k = 1 W/(m·K), area 0.01 m² and a 10 K temperature difference transfers 50 W in steady one-dimensional conduction. Contact resistances and edge losses are omitted." }, "url": "https://lemonergy.com/learn/glossary/thermal-conductivity/", "mentions": [ "heat-flux", "thermal-gradient" ] } }, { "id": "term:thermal-interface-material", "type": "Term", "label": "Thermal interface material", "properties": { "id": "thermal-interface-material", "name": "Thermal interface material", "abbr": "TIM", "aka": [ "gap filler" ], "section": "topic-thermal", "definition": "A soft, thermally conductive paste or pad that fills the gap between cells and the cooling plate so heat does not have to cross air. It is dispensed by the kilogram in a pack and is a surprising share of its cost.", "related": [ "cooling-plate", "thermal-management" ], "url": "https://lemonergy.com/learn/glossary/thermal-interface-material/", "mentions": [] } }, { "id": "term:cooling-plate", "type": "Term", "label": "Cooling plate", "properties": { "id": "cooling-plate", "name": "Cooling plate", "aka": [ "cold plate" ], "section": "topic-thermal", "definition": "A flat aluminium channel assembly under or between the cells through which coolant, usually a water–glycol mix, is pumped. Heat crosses from cell to plate through a thermal interface material; the plate also sets the pack’s temperature uniformity.", "related": [ "thermal-management", "thermal-interface-material", "immersion-cooling" ], "url": "https://lemonergy.com/learn/glossary/cooling-plate/", "mentions": [ "thermal-gradient", "coolant" ] } }, { "id": "term:heat-flux", "type": "Term", "label": "Heat flux", "properties": { "id": "heat-flux", "name": "Heat flux", "abbr": "q″", "section": "topic-thermal", "definition": "The rate of heat flow through a surface per unit area. Dividing a cell’s heat by its cooled area gives the flux the cooling must carry: a 21700 cell shedding 5 W through its roughly 46 cm² side sees about 1 kW/m². Cooling only one face concentrates the flux and steepens the gradient inside.", "formula": "q″ = Q / A", "unit": "W/m²", "related": [ "heat-transfer-coefficient", "thermal-conductivity", "thermal-resistance", "thermal-gradient", "cooling-plate" ], "example": { "title": "Compare equal heat across different areas", "text": "A 10 W heat flow spread uniformly across 0.02 m² has an average flux of 500 W/m². Concentrating the same heat into half the area doubles the average flux." }, "url": "https://lemonergy.com/learn/glossary/heat-flux/", "mentions": [ "cylindrical-cell" ] } }, { "id": "term:thermal-model", "type": "Term", "label": "Thermal model", "properties": { "id": "thermal-model", "name": "Thermal model", "aka": [ "lumped thermal model" ], "section": "topic-thermal", "definition": "A model of cell temperature: at its simplest one thermal mass with heat generation inside and convection outside, at its most detailed a 3D simulation of the pack. Temperature feeds back into every rate, so electrical and thermal models are usually solved together.", "related": [ "heat-generation", "thermal-management", "arrhenius", "newman-model", "thermal-characterisation" ], "url": "https://lemonergy.com/learn/glossary/thermal-model/", "mentions": [ "thermal-mass", "heat-transfer-modes" ] } }, { "id": "term:watt", "type": "Term", "label": "Watt", "properties": { "id": "watt", "name": "Watt", "abbr": "W", "section": "topic-units", "definition": "The SI unit of power: one joule per second, or in a circuit, volts times amperes. A cell delivering 20 A at 3.6 V is supplying 72 W.", "formula": "P = V × I", "unit": "W", "related": [ "power", "watt-hour", "specific-power" ], "example": { "title": "Calculate electrical power", "text": "At a particular instant, a terminal voltage of 12 V and current magnitude of 3 A correspond to 36 W. State whether the battery is receiving or supplying that power." }, "url": "https://lemonergy.com/learn/glossary/watt/", "mentions": [ "joule" ] } }, { "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
" } }, { "id": "reference:openstax-heat", "type": "Reference", "label": "University Physics Volume 2, §1.6: Mechanisms of Heat Transfer", "properties": { "title": "University Physics Volume 2, §1.6: Mechanisms of Heat Transfer", "publisher": "OpenStax, Rice University", "url": "https://openstax.org/books/university-physics-volume-2/pages/1-6-mechanisms-of-heat-transfer", "type": "Textbook section", "scope": "Conduction, convection, radiation and thermal resistance.", "accessed": "2026-10-27" } } ] }