{
  "node": {
    "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": []
    }
  },
  "edges": [
    {
      "id": "edge:belongsTo/term:secondary-protection/topic:topic-pack",
      "source": "term:secondary-protection",
      "target": "topic:topic-pack",
      "type": "belongsTo",
      "properties": {
        "sourceFile": "terms.json"
      }
    },
    {
      "id": "edge:relatedTo/term:secondary-protection/term:protection-circuit",
      "source": "term:secondary-protection",
      "target": "term:protection-circuit",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:relatedTo/term:secondary-protection/term:overcharge",
      "source": "term:secondary-protection",
      "target": "term:overcharge",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:relatedTo/term:secondary-protection/term:fuse",
      "source": "term:secondary-protection",
      "target": "term:fuse",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:relatedTo/term:secondary-protection/term:thermal-cutoff",
      "source": "term:secondary-protection",
      "target": "term:thermal-cutoff",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:relatedTo/term:secondary-protection/term:overcurrent-protection",
      "source": "term:secondary-protection",
      "target": "term:overcurrent-protection",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    }
  ],
  "neighbors": [
    {
      "id": "topic:topic-pack",
      "type": "Topic",
      "label": "Modules, packs and battery management",
      "properties": {
        "id": "topic-pack",
        "name": "Modules, packs and battery management",
        "lede": "From a single cell to a working battery system, and the electronics that keep it safe.",
        "context": "Make series/parallel architecture explicit.",
        "example": "Twelve 3.6 V, 5 Ah cells in 6s2p give 21.6 V, 10 Ah and 216 Wh nominally before other restrictions.",
        "lesson_url": "https://lemonergy.com/learn/fundamentals/cell-architecture/",
        "lesson_label": "Open cell architecture"
      }
    },
    {
      "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:overcharge",
      "type": "Term",
      "label": "Overcharge",
      "properties": {
        "id": "overcharge",
        "name": "Overcharge",
        "section": "topic-charging",
        "definition": "Charging past the upper cutoff voltage. The positive electrode over-delithiates and releases oxygen, the electrolyte oxidises and lithium plates on the negative, so an unprotected overcharge can end in thermal runaway.",
        "related": [
          "cutoff-voltage",
          "thermal-runaway",
          "bms",
          "overcharge-test",
          "electrolyte-decomposition"
        ],
        "url": "https://lemonergy.com/learn/glossary/overcharge/",
        "mentions": [
          "electrode",
          "positive-electrode",
          "electrolyte"
        ]
      }
    },
    {
      "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: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": []
      }
    },
    {
      "id": "term:overcurrent-protection",
      "type": "Term",
      "label": "Overcurrent protection",
      "properties": {
        "id": "overcurrent-protection",
        "name": "Overcurrent protection",
        "abbr": "OCP",
        "aka": [
          "short-circuit protection",
          "discharge overcurrent",
          "charge overcurrent"
        ],
        "section": "topic-pack",
        "definition": "Opening a pack’s switches when current exceeds a set limit for longer than a set delay. Protection chips use tiers — a moderate overcurrent trips after milliseconds to seconds, a short circuit within microseconds — sensed across a shunt or the MOSFETs’ own on-resistance, with a fuse or PTC device as back-up.",
        "related": [
          "protection-circuit",
          "mosfet",
          "current-sensor",
          "fuse",
          "ptc",
          "short-circuit-test"
        ],
        "url": "https://lemonergy.com/learn/glossary/overcurrent-protection/",
        "mentions": [
          "short-circuit"
        ]
      }
    }
  ]
}