{ "node": { "id": "term:passive-thermal-management", "type": "Term", "label": "Passive thermal management", "properties": { "id": "passive-thermal-management", "name": "Passive thermal management", "aka": [ "passive cooling", "thermal insulation" ], "section": "topic-thermal", "definition": "Controlling battery temperature without pumps, fans or compressors. Heat leaves by conduction to the enclosure and natural convection, sometimes helped by fins or phase change material, while insulation slows heat gain in summer and keeps a parked pack warm in winter. It suits small, low-power packs such as phones and e-bikes, not fast-charging vehicles.", "related": [ "phase-change-material", "heat-sink", "thermal-management", "enclosure", "thermal-mass" ], "url": "https://lemonergy.com/learn/glossary/passive-thermal-management/", "mentions": [ "heat-transfer-modes" ] } }, "edges": [ { "id": "edge:4769", "source": "term:passive-thermal-management", "target": "topic:topic-thermal", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:4770", "source": "term:passive-thermal-management", "target": "term:phase-change-material", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:4771", "source": "term:passive-thermal-management", "target": "term:heat-sink", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:4772", "source": "term:passive-thermal-management", "target": "term:thermal-management", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:4773", "source": "term:passive-thermal-management", "target": "term:enclosure", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:4774", "source": "term:passive-thermal-management", "target": "term:thermal-mass", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/passive-thermal-management/heat-transfer-modes", "source": "term:passive-thermal-management", "target": "term:heat-transfer-modes", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:4776", "source": "term:passive-thermal-management", "target": "visual:thermal", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } }, { "id": "edge:4777", "source": "term:passive-thermal-management", "target": "reference:openstax-heat", "type": "cites", "properties": { "sourceFile": "wiki-references.json", "scope": "direct technical reference" } } ], "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:phase-change-material", "type": "Term", "label": "Phase change material", "properties": { "id": "phase-change-material", "name": "Phase change material", "abbr": "PCM", "aka": [ "paraffin wax", "latent heat storage" ], "section": "topic-thermal", "definition": "A material that melts at a chosen temperature, around 30–45 °C for batteries, absorbing a large latent heat — roughly 200 J/g for paraffin wax — with little temperature rise. Packed around cells, often in a graphite matrix to lift its poor conductivity, it caps peaks during short heavy loads, but it must be cooled to reset and adds mass.", "related": [ "passive-thermal-management", "thermal-mass", "thermal-management", "thermal-conductivity" ], "url": "https://lemonergy.com/learn/glossary/phase-change-material/", "mentions": [ "graphite" ] } }, { "id": "term:heat-sink", "type": "Term", "label": "Heat sink", "properties": { "id": "heat-sink", "name": "Heat sink", "aka": [ "fins", "cooling fins", "finned heat sink" ], "section": "topic-thermal", "definition": "A metal body, often extruded aluminium with fins, that draws heat from a component and enlarges the surface it can lose that heat from. Fins multiply the area for convection to air; in batteries heat sinks serve air-cooled cell blocks and, above all, the balancing resistors and power switches of the BMS and DC/DC converter.", "related": [ "heat-transfer-coefficient", "radiator", "passive-thermal-management", "cell-balancing", "heat-pipe" ], "url": "https://lemonergy.com/learn/glossary/heat-sink/", "mentions": [ "bms", "dc-dc-converter", "heat-transfer-modes" ] } }, { "id": "term:thermal-management", "type": "Term", "label": "Thermal management", "properties": { "id": "thermal-management", "name": "Thermal management", "abbr": "TMS", "aka": [ "battery thermal management system", "BTMS" ], "section": "topic-thermal", "definition": "Keeping cells in their comfortable range, roughly 15–35 °C, and within a few degrees of each other: liquid cooling plates, refrigerant plates or immersion for heat removal, and heaters or waste heat for warming before fast charging in the cold.", "related": [ "cooling-plate", "thermal-interface-material", "operating-temperature", "heat-generation", "preconditioning", "temperature-sensor" ], "url": "https://lemonergy.com/learn/glossary/thermal-management/", "mentions": [ "fast-charging" ] } }, { "id": "term:enclosure", "type": "Term", "label": "Enclosure", "properties": { "id": "enclosure", "name": "Enclosure", "aka": [ "battery housing", "battery tray" ], "section": "topic-pack", "definition": "The sealed case that carries the modules, protects them in a crash, keeps water out to an IP67 rating or better and vents gas in a thermal event. In many cars it is a structural part of the body.", "related": [ "pack", "ip-rating", "cell-to-chassis", "venting", "gigacasting", "ul-94" ], "url": "https://lemonergy.com/learn/glossary/enclosure/", "mentions": [] } }, { "id": "term:thermal-mass", "type": "Term", "label": "Thermal mass", "properties": { "id": "thermal-mass", "name": "Thermal mass", "aka": [ "thermal inertia", "thermal time constant" ], "section": "topic-thermal", "definition": "A body’s total heat capacity seen as a buffer against temperature change. A 500 kg pack at about 1 kJ/(kg·K) stores roughly 500 kJ per kelvin, so 10 kW of uncooled heat warms it only about 1.2 K a minute. Together with the thermal resistance to the coolant it sets the pack’s thermal time constant.", "formula": "τ = m·cₚ·R_th", "related": [ "specific-heat-capacity", "thermal-resistance", "thermal-model", "phase-change-material", "thermal-management" ], "example": { "title": "Calculate a thermal time constant", "text": "With mass 0.5 kg, cₚ = 900 J/(kg·K) and R_th = 2 K/W, the lumped thermal time constant is 900 s, or 15 min. The calculation assumes a nearly uniform internal temperature." }, "url": "https://lemonergy.com/learn/glossary/thermal-mass/", "mentions": [] } }, { "id": "term:heat-transfer-modes", "type": "Term", "label": "Heat transfer modes", "properties": { "id": "heat-transfer-modes", "name": "Heat transfer modes", "aka": [ "conduction", "convection", "thermal radiation" ], "section": "topic-thermal", "definition": "The three ways heat moves: conduction through solids and still fluids, convection carried by a moving fluid, and radiation emitted as infrared by every warm surface. In a pack, conduction takes heat from the cell into the cooling plate and convection carries it away in the coolant; radiation matters mainly at the high temperatures of thermal runaway.", "related": [ "thermal-conductivity", "heat-transfer-coefficient", "thermography", "cooling-plate", "thermal-propagation" ], "url": "https://lemonergy.com/learn/glossary/heat-transfer-modes/", "mentions": [ "thermal-runaway" ] } }, { "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" } } ] }