{
  "node": {
    "id": "term:battery-disconnect-unit",
    "type": "Term",
    "label": "Battery disconnect unit",
    "properties": {
      "id": "battery-disconnect-unit",
      "name": "Battery disconnect unit",
      "abbr": "BDU",
      "aka": [
        "battery junction box"
      ],
      "section": "topic-hvsafety",
      "definition": "The box inside the pack that holds the contactors, pre-charge circuit, main fuse or pyrofuse and current sensor, where the pack’s high-voltage connections are made and broken.",
      "related": [
        "contactor",
        "pre-charge",
        "fuse",
        "pyrofuse",
        "current-sensor"
      ],
      "url": "https://lemonergy.com/learn/glossary/battery-disconnect-unit/",
      "mentions": []
    }
  },
  "edges": [
    {
      "id": "edge:2892",
      "source": "term:battery-disconnect-unit",
      "target": "topic:topic-hvsafety",
      "type": "belongsTo",
      "properties": {
        "sourceFile": "terms.json"
      }
    },
    {
      "id": "edge:2893",
      "source": "term:battery-disconnect-unit",
      "target": "term:contactor",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:2894",
      "source": "term:battery-disconnect-unit",
      "target": "term:pre-charge",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:2895",
      "source": "term:battery-disconnect-unit",
      "target": "term:fuse",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:2896",
      "source": "term:battery-disconnect-unit",
      "target": "term:pyrofuse",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:2897",
      "source": "term:battery-disconnect-unit",
      "target": "term:current-sensor",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    }
  ],
  "neighbors": [
    {
      "id": "topic:topic-hvsafety",
      "type": "Topic",
      "label": "High-voltage and functional safety",
      "properties": {
        "id": "topic-hvsafety",
        "name": "High-voltage and functional safety",
        "lede": "Keeping people safe from the pack’s voltage and keeping its electronics safe when they fail: insulation, switching, fusing and the functional-safety process.",
        "context": "Relate protection to faults, detection and response.",
        "example": "Normal-operation current limits do not demonstrate correct contactor behavior under a welded-contact or sensor fault.",
        "lesson_url": "https://lemonergy.com/learn/fundamentals/battery-basics/",
        "lesson_label": "Open battery basics"
      }
    },
    {
      "id": "term:contactor",
      "type": "Term",
      "label": "Contactor",
      "properties": {
        "id": "contactor",
        "name": "Contactor",
        "section": "topic-hvsafety",
        "definition": "A heavy-duty electrically operated switch that connects the pack to the vehicle or inverter and opens it on fault or shutdown. Packs use at least two, one per pole, plus a pre-charge path to avoid welding them on the first connection.",
        "related": [
          "pre-charge",
          "battery-disconnect-unit",
          "pyrofuse",
          "bms"
        ],
        "url": "https://lemonergy.com/learn/glossary/contactor/",
        "mentions": [
          "inverter"
        ]
      }
    },
    {
      "id": "term:pre-charge",
      "type": "Term",
      "label": "Pre-charge circuit",
      "properties": {
        "id": "pre-charge",
        "name": "Pre-charge circuit",
        "section": "topic-hvsafety",
        "definition": "A resistor and small contactor that charge the inverter’s capacitors slowly before the main contactor closes. Without it the inrush into empty capacitors can reach thousands of amperes and weld the main contactor shut.",
        "related": [
          "contactor",
          "battery-disconnect-unit",
          "inverter"
        ],
        "url": "https://lemonergy.com/learn/glossary/pre-charge/",
        "mentions": [
          "inrush-current"
        ]
      }
    },
    {
      "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:pyrofuse",
      "type": "Term",
      "label": "Pyrofuse",
      "properties": {
        "id": "pyrofuse",
        "name": "Pyrofuse",
        "aka": [
          "pyrotechnic disconnect"
        ],
        "section": "topic-hvsafety",
        "definition": "A high-voltage disconnect fired by a small pyrotechnic charge on command, typically from the airbag controller in a crash. It cuts the pack from the vehicle in milliseconds, faster and more reliably than a contactor can open under fault current.",
        "related": [
          "fuse",
          "contactor",
          "battery-disconnect-unit",
          "high-voltage-interlock"
        ],
        "url": "https://lemonergy.com/learn/glossary/pyrofuse/",
        "mentions": []
      }
    },
    {
      "id": "term:current-sensor",
      "type": "Term",
      "label": "Current sensor",
      "properties": {
        "id": "current-sensor",
        "name": "Current sensor",
        "aka": [
          "shunt",
          "Hall sensor"
        ],
        "section": "topic-pack",
        "definition": "The device that measures pack current for coulomb counting and protection: a precision shunt resistor read by an amplifier, or a Hall-effect sensor around the cable. Offset error in this sensor is what makes SOC drift between OCV corrections.",
        "related": [
          "coulomb-counting",
          "bms",
          "battery-disconnect-unit",
          "state-of-charge"
        ],
        "url": "https://lemonergy.com/learn/glossary/current-sensor/",
        "mentions": [
          "coulomb",
          "open-circuit-voltage"
        ]
      }
    }
  ]
}