{ "node": { "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": [] } }, "edges": [ { "id": "edge:2845", "source": "term:cell-supervision-circuit", "target": "topic:topic-pack", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:2846", "source": "term:cell-supervision-circuit", "target": "term:bms", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:2847", "source": "term:cell-supervision-circuit", "target": "term:cell-balancing", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:2848", "source": "term:cell-supervision-circuit", "target": "term:isospi", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:2849", "source": "term:cell-supervision-circuit", "target": "term:voltage-sense", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:2850", "source": "term:cell-supervision-circuit", "target": "term:afe", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:2851", "source": "term:cell-supervision-circuit", "target": "term:wireless-bms", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:2852", "source": "term:cell-supervision-circuit", "target": "visual:balancing", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } }, { "id": "edge:2853", "source": "term:cell-supervision-circuit", "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: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" ] } }, { "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:isospi", "type": "Term", "label": "isoSPI", "properties": { "id": "isospi", "name": "isoSPI", "aka": [ "daisy-chain interface" ], "section": "topic-pack", "definition": "A transformer-isolated, two-wire version of the SPI interface used to chain cell-monitoring chips across modules that sit at different voltages. It carries their measurements to the BMS controller without a separate isolated CAN node per module.", "related": [ "cell-supervision-circuit", "bms", "can-bus" ], "url": "https://lemonergy.com/learn/glossary/isospi/", "mentions": [] } }, { "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:afe", "type": "Term", "label": "Analog front end", "properties": { "id": "afe", "name": "Analog front end", "abbr": "AFE", "aka": [ "cell monitoring IC", "battery monitor IC", "BMIC" ], "section": "topic-data", "definition": "The integrated circuit that measures a stack of series cells — typically 6 to 18 per chip — with millivolt accuracy, reads thermistors, switches balancing and talks to the controller over an isolated daisy chain. It is the part of a BMS that touches the cells, and its accuracy limits how well SOC can be known.", "related": [ "cell-supervision-circuit", "isospi", "voltage-sense", "cell-balancing", "adc", "bmu" ], "url": "https://lemonergy.com/learn/glossary/afe/", "mentions": [ "state-of-charge", "bms" ] } }, { "id": "term:wireless-bms", "type": "Term", "label": "Wireless BMS", "properties": { "id": "wireless-bms", "name": "Wireless BMS", "abbr": "wBMS", "section": "topic-pack", "definition": "A pack architecture in which each cell supervision circuit talks to the controller by radio instead of a wiring harness, saving cable, connectors and assembly time. It needs its own redundancy and security design to reach the same safety level.", "related": [ "cell-supervision-circuit", "bms", "isospi" ], "url": "https://lemonergy.com/learn/glossary/wireless-bms/", "mentions": [ "wiring-harness" ] } }, { "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": "
Four cells before balancing
Four cells before balancingCell number versus Cell voltage (V). Individual voltages; Average; Example ceiling. Interpretation follows the graphs.3.713.851.7542.54.153.254.34Cell numberCell voltage (V)
Individual voltagesAverage (dashed)Example ceiling
" } }, { "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" } } ] }