{
  "node": {
    "id": "term:contactor-weld-detection",
    "type": "Term",
    "label": "Contactor weld detection",
    "properties": {
      "id": "contactor-weld-detection",
      "name": "Contactor weld detection",
      "aka": [
        "welded contactor",
        "stuck contactor diagnostic",
        "contactor diagnostics"
      ],
      "section": "topic-hvsafety",
      "definition": "A diagnostic that checks a contactor really opened when told to. The BMS compares voltages on each side of each contactor — if the load side still shows pack voltage after opening, the contacts have welded — or reads mirror auxiliary contacts. A welded contactor is latched as a fault, because the pack can no longer be fully disconnected.",
      "related": [
        "contactor",
        "pre-charge",
        "battery-disconnect-unit",
        "dtc",
        "contactor-arc-suppression"
      ],
      "url": "https://lemonergy.com/learn/glossary/contactor-weld-detection/",
      "mentions": [
        "pack-voltage",
        "bms"
      ]
    }
  },
  "edges": [
    {
      "id": "edge:5106",
      "source": "term:contactor-weld-detection",
      "target": "topic:topic-hvsafety",
      "type": "belongsTo",
      "properties": {
        "sourceFile": "terms.json"
      }
    },
    {
      "id": "edge:5107",
      "source": "term:contactor-weld-detection",
      "target": "term:contactor",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5108",
      "source": "term:contactor-weld-detection",
      "target": "term:pre-charge",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5109",
      "source": "term:contactor-weld-detection",
      "target": "term:battery-disconnect-unit",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5110",
      "source": "term:contactor-weld-detection",
      "target": "term:dtc",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5111",
      "source": "term:contactor-weld-detection",
      "target": "term:contactor-arc-suppression",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:mentions/contactor-weld-detection/pack-voltage",
      "source": "term:contactor-weld-detection",
      "target": "term:pack-voltage",
      "type": "mentions",
      "properties": {
        "sourceFile": "terms.json",
        "method": "build_glossary.mention_index + mentions",
        "field": "definition",
        "meaning": "Text mention; not a causal claim"
      }
    },
    {
      "id": "edge:mentions/contactor-weld-detection/bms",
      "source": "term:contactor-weld-detection",
      "target": "term:bms",
      "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-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: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": []
      }
    },
    {
      "id": "term:dtc",
      "type": "Term",
      "label": "Diagnostic trouble code",
      "properties": {
        "id": "dtc",
        "name": "Diagnostic trouble code",
        "abbr": "DTC",
        "aka": [
          "fault code"
        ],
        "section": "topic-data",
        "definition": "A coded fault a controller stores when a check fails — a cell overvoltage, a sensor out of range, an isolation fault — with a status and often a snapshot of conditions when it occurred. Reading and interpreting DTCs is the first step of any battery root-cause analysis.",
        "related": [
          "uds",
          "bmu",
          "insulation-resistance",
          "freeze-frame"
        ],
        "url": "https://lemonergy.com/learn/glossary/dtc/",
        "mentions": [
          "insulation-fault"
        ]
      }
    },
    {
      "id": "term:contactor-arc-suppression",
      "type": "Term",
      "label": "Contactor arc suppression",
      "properties": {
        "id": "contactor-arc-suppression",
        "name": "Contactor arc suppression",
        "aka": [
          "magnetic blow-out",
          "arc quenching",
          "arc chute",
          "gas-filled contactor"
        ],
        "section": "topic-hvsafety",
        "definition": "The means by which a high-voltage DC contactor breaks current under load. Permanent magnets push the arc sideways to stretch and cool it — so many contactors are polarised and break less current in reverse — and hermetically sealed chambers filled with hydrogen or hydrogen–nitrogen gas cool the arc and keep the contacts clean.",
        "related": [
          "contactor",
          "arcing",
          "contactor-weld-detection",
          "battery-disconnect-unit",
          "pyrofuse"
        ],
        "url": "https://lemonergy.com/learn/glossary/contactor-arc-suppression/",
        "mentions": []
      }
    },
    {
      "id": "term:pack-voltage",
      "type": "Term",
      "label": "Pack voltage",
      "properties": {
        "id": "pack-voltage",
        "name": "Pack voltage",
        "aka": [
          "400 V system",
          "800 V system"
        ],
        "section": "topic-pack",
        "definition": "The nominal voltage of the full series string, about 400 V in most electric cars and 800 V in newer ones. Doubling the voltage halves the current for the same power, so cables, connectors and losses shrink and charging can be faster.",
        "unit": "V",
        "related": [
          "series-parallel",
          "dc-fast-charging",
          "high-voltage-interlock",
          "insulation-resistance"
        ],
        "url": "https://lemonergy.com/learn/glossary/pack-voltage/",
        "mentions": [
          "nominal-voltage",
          "string"
        ]
      }
    },
    {
      "id": "term:bms",
      "type": "Term",
      "label": "Battery management system",
      "properties": {
        "id": "bms",
        "name": "Battery management system",
        "abbr": "BMS",
        "section": "topic-pack",
        "definition": "The electronics and software that keep a battery inside its safe window: measuring every cell voltage and many temperatures, estimating SOC and SOH, balancing cells, computing current limits, controlling the contactors and reporting over the vehicle network.",
        "related": [
          "state-of-charge",
          "cell-balancing",
          "state-of-power",
          "cell-supervision-circuit",
          "contactor",
          "can-bus"
        ],
        "lesson": "fundamentals/battery-basics/#cell-module-pack",
        "url": "https://lemonergy.com/learn/glossary/bms/",
        "mentions": [
          "state-of-health",
          "cell-voltage"
        ]
      }
    }
  ]
}