{
  "node": {
    "id": "term:hot-spot",
    "type": "Term",
    "label": "Hot spot",
    "properties": {
      "id": "hot-spot",
      "name": "Hot spot",
      "aka": [
        "hotspot"
      ],
      "section": "topic-thermal",
      "definition": "A small region that runs markedly hotter than its surroundings — near a tab, at a high-resistance weld or busbar joint, in the centre of a large cell or around an internal short. Because aging speeds up roughly twofold for every 10 °C, that spot ages fastest, and a temperature sensor a few centimetres away may not see it.",
      "related": [
        "thermal-gradient",
        "joule-heating",
        "temperature-sensor",
        "thermography",
        "arrhenius",
        "thermal-runaway"
      ],
      "url": "https://lemonergy.com/learn/glossary/hot-spot/",
      "mentions": [
        "busbar"
      ]
    }
  },
  "edges": [
    {
      "id": "edge:4620",
      "source": "term:hot-spot",
      "target": "topic:topic-thermal",
      "type": "belongsTo",
      "properties": {
        "sourceFile": "terms.json"
      }
    },
    {
      "id": "edge:4621",
      "source": "term:hot-spot",
      "target": "term:thermal-gradient",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:4622",
      "source": "term:hot-spot",
      "target": "term:joule-heating",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:4623",
      "source": "term:hot-spot",
      "target": "term:temperature-sensor",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:4624",
      "source": "term:hot-spot",
      "target": "term:thermography",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:4625",
      "source": "term:hot-spot",
      "target": "term:arrhenius",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:4626",
      "source": "term:hot-spot",
      "target": "term:thermal-runaway",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:mentions/hot-spot/busbar",
      "source": "term:hot-spot",
      "target": "term:busbar",
      "type": "mentions",
      "properties": {
        "sourceFile": "terms.json",
        "method": "build_glossary.mention_index + mentions",
        "field": "definition",
        "meaning": "Text mention; not a causal claim"
      }
    }
  ],
  "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:thermal-gradient",
      "type": "Term",
      "label": "Thermal gradient",
      "properties": {
        "id": "thermal-gradient",
        "name": "Thermal gradient",
        "aka": [
          "temperature gradient",
          "temperature spread",
          "temperature uniformity"
        ],
        "section": "topic-thermal",
        "definition": "A change of temperature with position — within a cell from core to surface, or across a pack from coolant inlet to outlet. Packs are commonly designed to keep cells within about 5 °C of each other, because warmer cells age faster and, in parallel, carry more current, so a gradient grows into an imbalance.",
        "related": [
          "hot-spot",
          "cell-to-cell-variation",
          "cooling-plate",
          "thermal-management",
          "biot-number"
        ],
        "url": "https://lemonergy.com/learn/glossary/thermal-gradient/",
        "mentions": []
      }
    },
    {
      "id": "term:joule-heating",
      "type": "Term",
      "label": "Joule heating",
      "properties": {
        "id": "joule-heating",
        "name": "Joule heating",
        "aka": [
          "ohmic heating",
          "resistive heating",
          "I²R loss"
        ],
        "section": "topic-thermal",
        "definition": "Heat produced by current flowing through a resistance, equal to the current squared times the resistance. Doubling the current quadruples it: a 1 mΩ cell gives 10 W at 100 A but 40 W at 200 A. It dominates heat generation at high C-rates and also warms busbars, welds and connectors.",
        "formula": "P = I²·R",
        "unit": "W",
        "related": [
          "heat-generation",
          "internal-resistance",
          "busbar",
          "hot-spot",
          "ohms-law"
        ],
        "example": {
          "title": "See the squared-current penalty",
          "text": "A 10 mΩ resistance dissipates 1 W at 10 A and 4 W at 20 A. Doubling current quadruples resistive heat when resistance stays constant."
        },
        "url": "https://lemonergy.com/learn/glossary/joule-heating/",
        "mentions": []
      }
    },
    {
      "id": "term:temperature-sensor",
      "type": "Term",
      "label": "Temperature sensor",
      "properties": {
        "id": "temperature-sensor",
        "name": "Temperature sensor",
        "abbr": "NTC",
        "aka": [
          "thermistor"
        ],
        "section": "topic-thermal",
        "definition": "Usually a negative-temperature-coefficient thermistor glued to a busbar or cell surface, with a few per module. Because sensors read the surface, the hottest point inside a cell can run several degrees higher than the BMS sees.",
        "unit": "°C",
        "related": [
          "bms",
          "thermal-management",
          "operating-temperature",
          "derating",
          "thermocouples-rtds",
          "virtual-temperature-sensor"
        ],
        "url": "https://lemonergy.com/learn/glossary/temperature-sensor/",
        "mentions": [
          "busbar"
        ]
      }
    },
    {
      "id": "term:thermography",
      "type": "Term",
      "label": "Thermography",
      "properties": {
        "id": "thermography",
        "name": "Thermography",
        "aka": [
          "infrared thermography",
          "thermal imaging",
          "IR camera"
        ],
        "section": "topic-thermal",
        "definition": "Imaging surface temperature with an infrared camera, which converts the radiation a surface emits into a temperature map. It reveals hot welds, busbar joints and uneven cell heating at a glance, but bare metal reflects more than it emits, so shiny surfaces are usually coated matt black before measuring.",
        "related": [
          "hot-spot",
          "heat-transfer-modes",
          "temperature-sensor",
          "thermal-gradient",
          "laser-welding"
        ],
        "url": "https://lemonergy.com/learn/glossary/thermography/",
        "mentions": [
          "busbar"
        ]
      }
    },
    {
      "id": "term:arrhenius",
      "type": "Term",
      "label": "Arrhenius law",
      "properties": {
        "id": "arrhenius",
        "name": "Arrhenius law",
        "section": "topic-aging",
        "definition": "The rule that a rate constant is proportional to exp(−Ea/RT), so a thermally activated reaction speeds up steeply with temperature. Near room temperature many degradation reactions roughly double their rate for every +10 °C.",
        "formula": "k = A·exp(−Eₐ/RT)",
        "related": [
          "activation-energy",
          "calendar-aging",
          "operating-temperature",
          "accelerated-aging",
          "celsius-kelvin"
        ],
        "lesson": "fundamentals/battery-aging/#arrhenius",
        "example": {
          "title": "Compare reaction-rate factors",
          "text": "For an illustrative activation energy of 40 kJ/mol, increasing temperature from 25 °C to 35 °C multiplies the modeled rate by about 1.69. Convert both temperatures to kelvin before evaluating the exponential."
        },
        "notes": [
          "A reaction-rate factor alone is not a prediction of battery lifetime."
        ],
        "url": "https://lemonergy.com/learn/glossary/arrhenius/",
        "mentions": []
      }
    },
    {
      "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:busbar",
      "type": "Term",
      "label": "Busbar",
      "properties": {
        "id": "busbar",
        "name": "Busbar",
        "section": "topic-pack",
        "definition": "A rigid copper or aluminium conductor that joins cell terminals into series and parallel groups, and modules into the pack. Its cross-section is sized for current and heating, and its joints — welded or bolted — are a classic source of resistance and failure.",
        "related": [
          "series-parallel",
          "terminal",
          "laser-welding",
          "internal-resistance",
          "wire-bonding"
        ],
        "url": "https://lemonergy.com/learn/glossary/busbar/",
        "mentions": []
      }
    }
  ]
}