{ "node": { "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" ] } }, "edges": [ { "id": "edge:4745", "source": "term:heat-sink", "target": "topic:topic-thermal", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:4746", "source": "term:heat-sink", "target": "term:heat-transfer-coefficient", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:4747", "source": "term:heat-sink", "target": "term:radiator", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:4748", "source": "term:heat-sink", "target": "term:passive-thermal-management", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:4749", "source": "term:heat-sink", "target": "term:cell-balancing", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:4750", "source": "term:heat-sink", "target": "term:heat-pipe", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/heat-sink/bms", "source": "term:heat-sink", "target": "term:bms", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:mentions/heat-sink/dc-dc-converter", "source": "term:heat-sink", "target": "term:dc-dc-converter", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:mentions/heat-sink/heat-transfer-modes", "source": "term:heat-sink", "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:4754", "source": "term:heat-sink", "target": "visual:thermal", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } }, { "id": "edge:4755", "source": "term:heat-sink", "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:heat-transfer-coefficient", "type": "Term", "label": "Heat transfer coefficient", "properties": { "id": "heat-transfer-coefficient", "name": "Heat transfer coefficient", "abbr": "h", "aka": [ "convection coefficient", "film coefficient" ], "section": "topic-thermal", "definition": "The heat carried away per unit area per kelvin of difference between a surface and the fluid passing it. Typical values are 5–25 W/(m²·K) for still air, 25–250 for forced air and hundreds to thousands for pumped liquid, which is why fast-charging packs are liquid-cooled. Thermal models use it as their cooling boundary.", "formula": "Q = h·A·ΔT", "unit": "W/(m²·K)", "related": [ "heat-transfer-modes", "heat-flux", "biot-number", "thermal-model", "cooling-plate", "coolant" ], "example": { "title": "Estimate convective cooling", "text": "For an illustrative h = 20 W/(m²·K), area 0.1 m² and surface-to-fluid temperature difference 10 K, hAΔT gives 20 W of cooling. The coefficient depends on the actual flow and geometry." }, "url": "https://lemonergy.com/learn/glossary/heat-transfer-coefficient/", "mentions": [] } }, { "id": "term:radiator", "type": "Term", "label": "Radiator", "properties": { "id": "radiator", "name": "Radiator", "section": "topic-thermal", "definition": "A finned coolant-to-air heat exchanger, usually behind the vehicle’s front grille, through which a fan draws air. It can only cool the coolant to a few degrees above the outside air, so it handles the battery in mild weather and the chiller takes over when it is hot or the charging load is high.", "related": [ "heat-exchanger", "chiller", "coolant", "heat-sink", "thermal-management" ], "url": "https://lemonergy.com/learn/glossary/radiator/", "mentions": [] } }, { "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" ] } }, { "id": "term:cell-balancing", "type": "Term", "label": "Cell balancing", "properties": { "id": "cell-balancing", "name": "Cell balancing", "section": "topic-state", "definition": "Equalising the state of charge of cells in series, since the pack is limited by its emptiest cell on discharge and its fullest on charge. Passive balancing bleeds charge from high cells through resistors; active balancing moves it between cells.", "related": [ "bms", "series-parallel", "state-of-charge", "cell-to-cell-variation" ], "example": { "title": "Pack average versus cell limits", "text": "Average pack SOC can look acceptable while one series cell reaches its voltage limit. One aggregate SOC state does not demonstrate cell balancing." }, "url": "https://lemonergy.com/learn/glossary/cell-balancing/", "mentions": [ "active-balancing" ] } }, { "id": "term:heat-pipe", "type": "Term", "label": "Heat pipe", "properties": { "id": "heat-pipe", "name": "Heat pipe", "aka": [ "vapour chamber" ], "section": "topic-thermal", "definition": "A sealed tube holding a little working fluid that evaporates at the hot end, condenses at the cold end and returns through a wick. It moves heat with an effective conductivity many times that of copper and little temperature drop. Common in electronics, it has been studied for spreading heat along cells, but packs still rely on cooling plates.", "related": [ "heat-sink", "thermal-conductivity", "cooling-plate", "passive-thermal-management" ], "url": "https://lemonergy.com/learn/glossary/heat-pipe/", "mentions": [] } }, { "id": "term:bms", "type": "Term", "label": "Battery management system", "properties": { "id": "bms", "name": "Battery management system", "abbr": "BMS", "section": "topic-pack", "definition": "The electronics and software that keep a battery inside its safe window: measuring every cell voltage and many temperatures, estimating SOC and SOH, balancing cells, computing current limits, controlling the contactors and reporting over the vehicle network.", "related": [ "state-of-charge", "cell-balancing", "state-of-power", "cell-supervision-circuit", "contactor", "can-bus" ], "lesson": "fundamentals/battery-basics/#cell-module-pack", "url": "https://lemonergy.com/learn/glossary/bms/", "mentions": [ "state-of-health", "cell-voltage" ] } }, { "id": "term:dc-dc-converter", "type": "Term", "label": "DC/DC converter", "properties": { "id": "dc-dc-converter", "name": "DC/DC converter", "section": "topic-pack", "definition": "The power electronics that step the high-voltage pack down to 12 V or 48 V for the auxiliary systems, replacing the alternator of a combustion car. Boost converters also appear between an 800 V pack and a 400 V charger.", "related": [ "auxiliary-battery", "inverter", "pack-voltage" ], "url": "https://lemonergy.com/learn/glossary/dc-dc-converter/", "mentions": [ "charger" ] } }, { "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" } } ] }