{
  "node": {
    "id": "term:thermal-cutoff",
    "type": "Term",
    "label": "Thermal cutoff",
    "properties": {
      "id": "thermal-cutoff",
      "name": "Thermal cutoff",
      "abbr": "TCO",
      "aka": [
        "thermal fuse",
        "bimetal protector",
        "thermal protector",
        "thermal switch"
      ],
      "section": "topic-safety",
      "definition": "A temperature-operated switch placed against the cells that opens the current path when they get too hot. One-shot thermal fuses melt a pellet or alloy link and stay open; bimetal protectors snap open at roughly 70–90 °C and close again on cooling. It backs up the electronic protection, especially in laptop and power-tool packs.",
      "related": [
        "ptc",
        "secondary-protection",
        "fuse",
        "protection-circuit",
        "thermal-runaway"
      ],
      "url": "https://lemonergy.com/learn/glossary/thermal-cutoff/",
      "mentions": []
    }
  },
  "edges": [
    {
      "id": "edge:belongsTo/term:thermal-cutoff/topic:topic-safety",
      "source": "term:thermal-cutoff",
      "target": "topic:topic-safety",
      "type": "belongsTo",
      "properties": {
        "sourceFile": "terms.json"
      }
    },
    {
      "id": "edge:relatedTo/term:thermal-cutoff/term:ptc",
      "source": "term:thermal-cutoff",
      "target": "term:ptc",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:relatedTo/term:thermal-cutoff/term:secondary-protection",
      "source": "term:thermal-cutoff",
      "target": "term:secondary-protection",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:relatedTo/term:thermal-cutoff/term:fuse",
      "source": "term:thermal-cutoff",
      "target": "term:fuse",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:relatedTo/term:thermal-cutoff/term:protection-circuit",
      "source": "term:thermal-cutoff",
      "target": "term:protection-circuit",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:relatedTo/term:thermal-cutoff/term:thermal-runaway",
      "source": "term:thermal-cutoff",
      "target": "term:thermal-runaway",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    }
  ],
  "neighbors": [
    {
      "id": "topic:topic-safety",
      "type": "Topic",
      "label": "Safety and abuse",
      "properties": {
        "id": "topic-safety",
        "name": "Safety and abuse",
        "lede": "How cells fail dangerously, how that is tested, and what is built in to stop it.",
        "context": "Connect mechanisms with appropriate test evidence.",
        "example": "A low normal-load temperature does not demonstrate thermal-runaway containment.",
        "lesson_url": "https://lemonergy.com/learn/fundamentals/battery-aging/",
        "lesson_label": "Open degradation mechanisms"
      }
    },
    {
      "id": "term:ptc",
      "type": "Term",
      "label": "Positive temperature coefficient device",
      "properties": {
        "id": "ptc",
        "name": "Positive temperature coefficient device",
        "abbr": "PTC",
        "section": "topic-safety",
        "definition": "A polymer element in series with a cell whose resistance jumps when it heats, choking an external short-circuit current. It resets as it cools, unlike a fuse, but adds resistance and does not help against internal faults.",
        "related": [
          "external-short-circuit",
          "fuse",
          "current-interrupt-device"
        ],
        "url": "https://lemonergy.com/learn/glossary/ptc/",
        "mentions": []
      }
    },
    {
      "id": "term:secondary-protection",
      "type": "Term",
      "label": "Secondary protection",
      "properties": {
        "id": "secondary-protection",
        "name": "Secondary protection",
        "aka": [
          "secondary protection IC",
          "self-control protector",
          "three-terminal fuse",
          "overvoltage protector",
          "chemical fuse"
        ],
        "section": "topic-pack",
        "definition": "A second, independent protection layer in a lithium-ion pack that acts if the primary protection circuit fails. A separate chip watches each cell’s voltage and, on overcharge, drives a heater inside a three-terminal fuse so that it blows for good; the same fuse also opens on overcurrent. Laptop and power-tool packs routinely carry one.",
        "related": [
          "protection-circuit",
          "overcharge",
          "fuse",
          "thermal-cutoff",
          "overcurrent-protection"
        ],
        "url": "https://lemonergy.com/learn/glossary/secondary-protection/",
        "mentions": []
      }
    },
    {
      "id": "term:fuse",
      "type": "Term",
      "label": "Fuse",
      "properties": {
        "id": "fuse",
        "name": "Fuse",
        "section": "topic-hvsafety",
        "definition": "A link that melts and opens the circuit when current exceeds its rating. Packs use a main fuse in the high-voltage path and often a small fuse on each parallel cell connection, so one shorted cell does not drain its neighbours into the fault.",
        "related": [
          "external-short-circuit",
          "pyrofuse",
          "battery-disconnect-unit",
          "series-parallel",
          "cell-level-fuse"
        ],
        "url": "https://lemonergy.com/learn/glossary/fuse/",
        "mentions": []
      }
    },
    {
      "id": "term:protection-circuit",
      "type": "Term",
      "label": "Protection circuit module",
      "properties": {
        "id": "protection-circuit",
        "name": "Protection circuit module",
        "abbr": "PCM",
        "aka": [
          "protection board",
          "PCB"
        ],
        "section": "topic-pack",
        "definition": "The small circuit on a consumer cell or pack that disconnects it on overvoltage, undervoltage, overcurrent or overtemperature, using MOSFETs as switches. It is the minimum BMS; it protects but does not estimate state or balance.",
        "related": [
          "bms",
          "overcharge",
          "over-discharge",
          "fuel-gauge",
          "secondary-protection",
          "overcurrent-protection"
        ],
        "url": "https://lemonergy.com/learn/glossary/protection-circuit/",
        "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"
        ]
      }
    }
  ]
}