{
  "node": {
    "id": "term:kelvin-sensing",
    "type": "Term",
    "label": "Kelvin sensing",
    "properties": {
      "id": "kelvin-sensing",
      "name": "Kelvin sensing",
      "aka": [
        "four-wire sensing",
        "four-terminal sensing",
        "4-wire measurement",
        "separate sense and balancing leads"
      ],
      "section": "topic-data",
      "definition": "Measuring voltage through a separate pair of leads that carry no current, so the drop along current-carrying wires and joints is left out. In a BMS, 100 mA of balancing current through 0.5 Ω of sense wire would add a 50 mV error, so designs either give balancing its own leads or pause balancing while measuring.",
      "related": [
        "voltage-sense",
        "cell-balancing",
        "current-sensor",
        "contact-resistance",
        "dcir",
        "thermoelectric-error"
      ],
      "url": "https://lemonergy.com/learn/glossary/kelvin-sensing/",
      "mentions": [
        "bms"
      ]
    }
  },
  "edges": [
    {
      "id": "edge:5269",
      "source": "term:kelvin-sensing",
      "target": "topic:topic-data",
      "type": "belongsTo",
      "properties": {
        "sourceFile": "terms.json"
      }
    },
    {
      "id": "edge:5270",
      "source": "term:kelvin-sensing",
      "target": "term:voltage-sense",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5271",
      "source": "term:kelvin-sensing",
      "target": "term:cell-balancing",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5272",
      "source": "term:kelvin-sensing",
      "target": "term:current-sensor",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5273",
      "source": "term:kelvin-sensing",
      "target": "term:contact-resistance",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5274",
      "source": "term:kelvin-sensing",
      "target": "term:dcir",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5275",
      "source": "term:kelvin-sensing",
      "target": "term:thermoelectric-error",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:mentions/kelvin-sensing/bms",
      "source": "term:kelvin-sensing",
      "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-data",
      "type": "Topic",
      "label": "Data, communication and electronics",
      "properties": {
        "id": "topic-data",
        "name": "Data, communication and electronics",
        "lede": "The control units, chips, protocols and file formats through which a battery is measured, controlled and logged.",
        "context": "Separate quantities from encoding and transport.",
        "example": "2500 in a log might mean 25.00 °C, 2.5 V or raw counts. Units and scale must accompany the value.",
        "lesson_url": "https://lemonergy.com/learn/fundamentals/battery-basics/",
        "lesson_label": "Open battery basics"
      }
    },
    {
      "id": "term:voltage-sense",
      "type": "Term",
      "label": "Voltage sensing",
      "properties": {
        "id": "voltage-sense",
        "name": "Voltage sensing",
        "aka": [
          "cell tap",
          "sense line"
        ],
        "section": "topic-pack",
        "definition": "Measuring each series cell group’s voltage through a wire or flexible circuit from its busbar to the monitoring chip. Millivolt accuracy matters because the BMS reads SOC and detects faults from these numbers.",
        "unit": "mV",
        "related": [
          "cell-supervision-circuit",
          "bms",
          "busbar",
          "open-circuit-voltage",
          "afe"
        ],
        "url": "https://lemonergy.com/learn/glossary/voltage-sense/",
        "mentions": [
          "state-of-charge"
        ]
      }
    },
    {
      "id": "term:cell-balancing",
      "type": "Term",
      "label": "Cell balancing",
      "properties": {
        "id": "cell-balancing",
        "name": "Cell balancing",
        "section": "topic-state",
        "definition": "Equalising the state of charge of cells in series, since the pack is limited by its emptiest cell on discharge and its fullest on charge. Passive balancing bleeds charge from high cells through resistors; active balancing moves it between cells.",
        "related": [
          "bms",
          "series-parallel",
          "state-of-charge",
          "cell-to-cell-variation"
        ],
        "example": {
          "title": "Pack average versus cell limits",
          "text": "Average pack SOC can look acceptable while one series cell reaches its voltage limit. One aggregate SOC state does not demonstrate cell balancing."
        },
        "url": "https://lemonergy.com/learn/glossary/cell-balancing/",
        "mentions": [
          "active-balancing"
        ]
      }
    },
    {
      "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"
        ]
      }
    },
    {
      "id": "term:contact-resistance",
      "type": "Term",
      "label": "Electrical contact resistance",
      "properties": {
        "id": "contact-resistance",
        "name": "Electrical contact resistance",
        "aka": [
          "contact resistance",
          "joint resistance",
          "constriction resistance"
        ],
        "section": "topic-pack",
        "definition": "The extra resistance where two conductors touch, because current passes only through microscopic contact spots and any oxide film on them. It falls with contact force and good plating and rises with corrosion and fretting. At 300 A a joint of 50 µΩ dissipates 4.5 W, enough to overheat a poorly cooled connection.",
        "formula": "P = I²·R_contact",
        "unit": "Ω",
        "related": [
          "bolted-busbar-joint",
          "busbar",
          "internal-resistance",
          "ohms-law",
          "kelvin-sensing"
        ],
        "example": {
          "title": "Find heating at a joint",
          "text": "An illustrative 0.5 mΩ joint carrying 100 A dissipates 5 W. Even a small contact resistance matters at high current; its actual temperature rise depends on the local thermal path."
        },
        "url": "https://lemonergy.com/learn/glossary/contact-resistance/",
        "mentions": []
      }
    },
    {
      "id": "term:dcir",
      "type": "Term",
      "label": "DC internal resistance",
      "properties": {
        "id": "dcir",
        "name": "DC internal resistance",
        "abbr": "DCIR",
        "aka": [
          "DC-IR",
          "pulse resistance"
        ],
        "section": "topic-testing",
        "definition": "Internal resistance measured from the voltage change during a current pulse of defined length, usually 10 s or 18 s. It is larger than the AC value because it includes charge-transfer and some diffusion, and it depends on SOC, temperature and pulse duration.",
        "unit": "mΩ",
        "related": [
          "internal-resistance",
          "acir",
          "hppc",
          "impedance-rise"
        ],
        "url": "https://lemonergy.com/learn/glossary/dcir/",
        "mentions": [
          "state-of-charge",
          "diffusion"
        ]
      }
    },
    {
      "id": "term:thermoelectric-error",
      "type": "Term",
      "label": "Thermoelectric voltage error",
      "properties": {
        "id": "thermoelectric-error",
        "name": "Thermoelectric voltage error",
        "aka": [
          "Seebeck error",
          "thermal EMF",
          "thermocouple effect"
        ],
        "section": "topic-data",
        "definition": "A small voltage, the Seebeck effect, that appears wherever two different metals meet at different temperatures. Negligible for cell voltages, it matters for shunt current sensing: on a 100 µΩ shunt each microvolt reads as 10 mA, which coulomb counting integrates into SOC drift. Manganin is used for shunts partly because its thermal EMF against copper is under 1 µV/K.",
        "related": [
          "current-sensor",
          "coulomb-counting",
          "adc",
          "kelvin-sensing",
          "state-of-charge"
        ],
        "url": "https://lemonergy.com/learn/glossary/thermoelectric-error/",
        "mentions": [
          "coulomb"
        ]
      }
    },
    {
      "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"
        ]
      }
    }
  ]
}