{
  "node": {
    "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"
      ]
    }
  },
  "edges": [
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      "id": "edge:2833",
      "source": "term:bms",
      "target": "topic:topic-pack",
      "type": "belongsTo",
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    },
    {
      "id": "edge:2834",
      "source": "term:bms",
      "target": "term:state-of-charge",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:2835",
      "source": "term:bms",
      "target": "term:cell-balancing",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:2836",
      "source": "term:bms",
      "target": "term:state-of-power",
      "type": "relatedTo",
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        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
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      "id": "edge:2837",
      "source": "term:bms",
      "target": "term:cell-supervision-circuit",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
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      "id": "edge:2838",
      "source": "term:bms",
      "target": "term:contactor",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:2839",
      "source": "term:bms",
      "target": "term:can-bus",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:mentions/bms/state-of-health",
      "source": "term:bms",
      "target": "term:state-of-health",
      "type": "mentions",
      "properties": {
        "sourceFile": "terms.json",
        "method": "build_glossary.mention_index + mentions",
        "field": "definition",
        "meaning": "Text mention; not a causal claim"
      }
    },
    {
      "id": "edge:mentions/bms/cell-voltage",
      "source": "term:bms",
      "target": "term:cell-voltage",
      "type": "mentions",
      "properties": {
        "sourceFile": "terms.json",
        "method": "build_glossary.mention_index + mentions",
        "field": "definition",
        "meaning": "Text mention; not a causal claim"
      }
    },
    {
      "id": "edge:2842",
      "source": "term:bms",
      "target": "lesson:fundamentals/battery-basics/",
      "type": "explainedIn",
      "properties": {
        "sourceFile": "terms.json",
        "url": "https://lemonergy.com/learn/fundamentals/battery-basics/#cell-module-pack"
      }
    },
    {
      "id": "edge:2843",
      "source": "term:bms",
      "target": "visual:balancing",
      "type": "illustratedBy",
      "properties": {
        "sourceFile": "visual-pages.json"
      }
    },
    {
      "id": "edge:2844",
      "source": "term:bms",
      "target": "reference:ti-bms",
      "type": "cites",
      "properties": {
        "sourceFile": "wiki-references.json",
        "scope": "direct technical reference"
      }
    }
  ],
  "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:state-of-charge",
      "type": "Term",
      "label": "State of charge",
      "properties": {
        "id": "state-of-charge",
        "name": "State of charge",
        "abbr": "SOC",
        "section": "topic-state",
        "definition": "How full a cell is, as a fraction of its available capacity. State of charge, like temperature, affects how fast a stored cell ages.",
        "unit": "%",
        "related": [
          "depth-of-discharge",
          "ocv-soc-curve",
          "coulomb-counting",
          "state-of-health",
          "bms"
        ],
        "lesson": "fundamentals/battery-aging/#storage-soc",
        "example": {
          "title": "Interpret a charge inventory",
          "text": "If available capacity is 5 Ah and 3 Ah remains by the chosen estimator, SOC is 60%. A different estimate of available capacity changes this percentage, so compare SOC values only with the capacity convention recorded."
        },
        "url": "https://lemonergy.com/learn/glossary/state-of-charge/",
        "mentions": [
          "usable-capacity"
        ]
      }
    },
    {
      "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:state-of-power",
      "type": "Term",
      "label": "State of power",
      "properties": {
        "id": "state-of-power",
        "name": "State of power",
        "abbr": "SOP",
        "section": "topic-state",
        "definition": "The maximum charge or discharge power a battery can deliver for the next few seconds without breaking a voltage, current or temperature limit. The BMS recomputes it continuously from SOC, temperature and resistance and sends it to the motor controller.",
        "unit": "W",
        "related": [
          "power",
          "state-of-charge",
          "continuous-current",
          "derating",
          "bms",
          "state-of-function"
        ],
        "url": "https://lemonergy.com/learn/glossary/state-of-power/",
        "mentions": []
      }
    },
    {
      "id": "term:cell-supervision-circuit",
      "type": "Term",
      "label": "Cell supervision circuit",
      "properties": {
        "id": "cell-supervision-circuit",
        "name": "Cell supervision circuit",
        "abbr": "CSC",
        "aka": [
          "cell monitoring unit",
          "CMU",
          "slave BMS"
        ],
        "section": "topic-pack",
        "definition": "The board on each module that measures its cell voltages and temperatures and switches its balancing resistors, reporting to the central BMS controller. It is usually built around a dedicated monitoring chip and linked by isoSPI or CAN.",
        "related": [
          "bms",
          "cell-balancing",
          "isospi",
          "voltage-sense",
          "afe",
          "wireless-bms"
        ],
        "url": "https://lemonergy.com/learn/glossary/cell-supervision-circuit/",
        "mentions": []
      }
    },
    {
      "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:can-bus",
      "type": "Term",
      "label": "CAN bus",
      "properties": {
        "id": "can-bus",
        "name": "CAN bus",
        "aka": [
          "Controller Area Network",
          "ISO 11898"
        ],
        "section": "topic-pack",
        "definition": "The serial network over which a BMS talks to the vehicle or inverter: a two-wire differential bus, defined in ISO 11898, carrying short prioritised messages at up to 1 Mbit/s, or faster with CAN FD. Every node hears every message, and a dominant bit wins arbitration without any collision.",
        "related": [
          "can-high-low",
          "can-fd",
          "termination-resistor",
          "bms",
          "lin-bus",
          "fms-interface"
        ],
        "url": "https://lemonergy.com/learn/glossary/can-bus/",
        "mentions": [
          "inverter"
        ]
      }
    },
    {
      "id": "term:state-of-health",
      "type": "Term",
      "label": "State of health",
      "properties": {
        "id": "state-of-health",
        "name": "State of health",
        "abbr": "SOH",
        "section": "topic-state",
        "definition": "A summary of how far a cell has aged, often expressed through remaining capacity or increased resistance compared with when it was new. By convention a cell has reached end of life at 80 % of its rated capacity.",
        "unit": "%",
        "related": [
          "capacity-fade",
          "impedance-rise",
          "end-of-life",
          "remaining-useful-life",
          "state-of-charge",
          "state-of-certified-energy"
        ],
        "lesson": "fundamentals/capacity-and-c-rate/#real-cells",
        "url": "https://lemonergy.com/learn/glossary/state-of-health/",
        "mentions": [
          "nominal-capacity"
        ]
      }
    },
    {
      "id": "term:cell-voltage",
      "type": "Term",
      "label": "Cell voltage",
      "properties": {
        "id": "cell-voltage",
        "name": "Cell voltage",
        "aka": [
          "electromotive force",
          "EMF"
        ],
        "section": "topic-electrochemistry",
        "definition": "The difference between the positive and negative electrode potentials at equilibrium: for NMC against graphite about 3.7 V. It is set by the chemistry, and the difference in Gibbs free energy of the cell reaction per unit charge.",
        "formula": "E = E₊ − E₋ = −ΔG / nF",
        "unit": "V",
        "related": [
          "electrode-potential",
          "gibbs-free-energy",
          "open-circuit-voltage",
          "nominal-voltage"
        ],
        "example": {
          "title": "Subtract equilibrium electrode potentials",
          "text": "If two illustrative electrode potentials are 4.0 V and 0.2 V versus the same reference, their equilibrium cell voltage is 3.8 V. Under load, resistance and polarization change the measured terminal voltage."
        },
        "url": "https://lemonergy.com/learn/glossary/cell-voltage/",
        "mentions": [
          "electrode",
          "negative-electrode",
          "graphite"
        ]
      }
    },
    {
      "id": "lesson:fundamentals/battery-basics/",
      "type": "Lesson",
      "label": "Lesson 0 · Battery basics",
      "properties": {
        "url": "https://lemonergy.com/learn/fundamentals/battery-basics/"
      }
    },
    {
      "id": "visual:balancing",
      "type": "Visual",
      "label": "The limiting cell matters",
      "properties": {
        "title": "The limiting cell matters",
        "summary": "A pack average can hide a cell that reaches its voltage limit first.",
        "readout": "Average: 3.93 V. Highest cell: 4.02 V. The highest cell can reach the charge limit first.",
        "formula": "V_max = max(V₁, V₂, …); V_average = ΣV_i / N",
        "note": "The 4.2 V ceiling is an example, not universal. Voltage alone does not uniquely determine SOC.",
        "software": {
          "status": "reference",
          "label": "Reference concept",
          "body": "Cell supervision uses individual voltages. The native Studio battery is an aggregate model; this chart does not claim it simulates cell balancing.",
          "href": "https://design.lemonergy.com/cosim.html?example=charging-home"
        },
        "html": "<figure class=\"visual-figure\"><figcaption>Four cells before balancing</figcaption><svg class=\"visual-chart\" viewBox=\"0 0 360 330\" role=\"img\" aria-labelledby=\"static-balancing-0-title static-balancing-0-desc\"><title id=\"static-balancing-0-title\">Four cells before balancing</title><desc id=\"static-balancing-0-desc\">Cell number versus Cell voltage (V). Individual voltages; Average; Example ceiling. Interpretation follows the graphs.</desc><path d=\"M74,238h268\" stroke=\"currentColor\" opacity=\".13\"/><text x=\"64\" y=\"242\" text-anchor=\"end\" font-size=\"13\" fill=\"currentColor\">3.7</text><text x=\"74\" y=\"265\" text-anchor=\"middle\" font-size=\"13\" fill=\"currentColor\">1</text><path d=\"M74,188.5h268\" stroke=\"currentColor\" opacity=\".13\"/><text x=\"64\" y=\"192.5\" text-anchor=\"end\" font-size=\"13\" fill=\"currentColor\">3.85</text><text x=\"141\" y=\"265\" text-anchor=\"middle\" font-size=\"13\" fill=\"currentColor\">1.75</text><path d=\"M74,139h268\" stroke=\"currentColor\" opacity=\".13\"/><text x=\"64\" y=\"143\" text-anchor=\"end\" font-size=\"13\" fill=\"currentColor\">4</text><text x=\"208\" y=\"265\" text-anchor=\"middle\" font-size=\"13\" fill=\"currentColor\">2.5</text><path d=\"M74,89.49999999999986h268\" stroke=\"currentColor\" opacity=\".13\"/><text x=\"64\" y=\"93.49999999999986\" text-anchor=\"end\" font-size=\"13\" fill=\"currentColor\">4.15</text><text x=\"275\" y=\"265\" text-anchor=\"middle\" font-size=\"13\" fill=\"currentColor\">3.25</text><path d=\"M74,40h268\" stroke=\"currentColor\" opacity=\".13\"/><text x=\"64\" y=\"44\" text-anchor=\"end\" font-size=\"13\" fill=\"currentColor\">4.3</text><text x=\"342\" y=\"265\" text-anchor=\"middle\" font-size=\"13\" fill=\"currentColor\">4</text><path d=\"M74,40v198h268\" fill=\"none\" stroke=\"currentColor\" opacity=\".3\"/><polyline fill=\"none\" stroke=\"#6953a8\" stroke-width=\"2.8\" points=\"74.00,172.00 163.33,158.80 252.67,185.20 342.00,132.40\"/><polyline fill=\"none\" stroke=\"#2459a8\" stroke-width=\"2.8\" stroke-dasharray=\"7 4\" points=\"74.00,162.10 342.00,162.10\"/><polyline fill=\"none\" stroke=\"#a45b2b\" stroke-width=\"2.8\" points=\"74.00,73.00 342.00,73.00\"/><text transform=\"translate(208 303)\" text-anchor=\"middle\" font-size=\"14\" fill=\"currentColor\"><tspan x=\"0\" dy=\"0\">Cell number</tspan></text><text transform=\"translate(20 139) rotate(-90)\" text-anchor=\"middle\" font-size=\"14\" fill=\"currentColor\"><tspan x=\"0\" dy=\"0\">Cell voltage (V)</tspan></text></svg><div class=\"visual-legend\"><span><i style=\"background:#6953a8\"></i>Individual voltages</span><span><i style=\"background:#2459a8\"></i>Average (dashed)</span><span><i style=\"background:#a45b2b\"></i>Example ceiling</span></div></figure>"
      }
    },
    {
      "id": "reference:ti-bms",
      "type": "Reference",
      "label": "Getting Started with the BQ76925",
      "properties": {
        "title": "Getting Started with the BQ76925",
        "publisher": "Texas Instruments",
        "url": "https://www.ti.com/lit/an/slua619b/slua619b.pdf",
        "type": "Application report",
        "scope": "A concrete BMS analog front-end example: cell voltage, current, temperature measurement and MCU integration.",
        "year": 2019,
        "accessed": "2026-10-27"
      }
    }
  ]
}