{
  "node": {
    "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": []
    }
  },
  "edges": [
    {
      "id": "edge:4628",
      "source": "term:thermal-gradient",
      "target": "topic:topic-thermal",
      "type": "belongsTo",
      "properties": {
        "sourceFile": "terms.json"
      }
    },
    {
      "id": "edge:4629",
      "source": "term:thermal-gradient",
      "target": "term:hot-spot",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:4630",
      "source": "term:thermal-gradient",
      "target": "term:cell-to-cell-variation",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:4631",
      "source": "term:thermal-gradient",
      "target": "term:cooling-plate",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:4632",
      "source": "term:thermal-gradient",
      "target": "term:thermal-management",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:4633",
      "source": "term:thermal-gradient",
      "target": "term:biot-number",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; 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: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"
        ]
      }
    },
    {
      "id": "term:cell-to-cell-variation",
      "type": "Term",
      "label": "Cell-to-cell variation",
      "properties": {
        "id": "cell-to-cell-variation",
        "name": "Cell-to-cell variation",
        "section": "topic-state",
        "definition": "The spread in capacity, resistance and self-discharge between nominally identical cells, from manufacturing and from unequal temperatures in service. It is why packs need balancing and why grading matches cells before assembly.",
        "related": [
          "cell-balancing",
          "grading",
          "end-of-line-testing",
          "thermal-management"
        ],
        "url": "https://lemonergy.com/learn/glossary/cell-to-cell-variation/",
        "mentions": [
          "self-discharge"
        ]
      }
    },
    {
      "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: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:biot-number",
      "type": "Term",
      "label": "Biot number",
      "properties": {
        "id": "biot-number",
        "name": "Biot number",
        "abbr": "Bi",
        "section": "topic-thermal",
        "definition": "The ratio of the resistance to heat conduction inside a body to the resistance to convection at its surface. Below about 0.1 the body heats almost uniformly and a lumped thermal model is adequate; large, strongly cooled cells with poor through-plane conductivity exceed it and need a model that resolves the internal gradient.",
        "formula": "Bi = h·L / k",
        "related": [
          "heat-transfer-coefficient",
          "thermal-conductivity",
          "thermal-model",
          "thermal-gradient"
        ],
        "example": {
          "title": "Check a lumped-temperature assumption",
          "text": "For h = 10 W/(m²·K), characteristic length L = 0.005 m and k = 1 W/(m·K), Bi = 0.05. Small Bi supports a lumped-temperature approximation; the characteristic length must match the geometry."
        },
        "url": "https://lemonergy.com/learn/glossary/biot-number/",
        "mentions": [
          "heat-transfer-modes"
        ]
      }
    }
  ]
}