{ "node": { "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" ] } }, "edges": [ { "id": "edge:160", "source": "term:voltage-sense", "target": "workflow:ohm-circuit", "type": "usedIn", "properties": { "sourceFile": "wiki-blocks.json" } }, { "id": "edge:2854", "source": "term:voltage-sense", "target": "topic:topic-pack", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:2855", "source": "term:voltage-sense", "target": "term:cell-supervision-circuit", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:2856", "source": "term:voltage-sense", "target": "term:bms", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:2857", "source": "term:voltage-sense", "target": "term:busbar", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:2858", "source": "term:voltage-sense", "target": "term:open-circuit-voltage", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:2859", "source": "term:voltage-sense", "target": "term:afe", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/voltage-sense/state-of-charge", "source": "term:voltage-sense", "target": "term:state-of-charge", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:2861", "source": "term:voltage-sense", "target": "visual:balancing", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } }, { "id": "edge:2862", "source": "term:voltage-sense", "target": "reference:ti-bms", "type": "cites", "properties": { "sourceFile": "wiki-references.json", "scope": "direct technical reference" } } ], "neighbors": [ { "id": "workflow:ohm-circuit", "type": "Workflow", "label": "Relate current and voltage", "properties": { "id": "ohm-circuit", "title": "Relate current and voltage", "kind": "studio", "summary": "Conserving components solve constitutive relations and node balance.", "steps": [ "Inspect source and resistor in the RC example.", "Compare branch current with resistor voltage." ], "example": "A 1 V drop across 2 Ω implies 0.5 A.", "observe": "Topology sets individual element voltages.", "limits": "The RC example includes a capacitor: transient current varies and source voltage is not always resistor voltage.", "url": "https://design.lemonergy.com/cosim.html?example=physical-rc", "label": "Open the electrical circuit", "evidence": [ "js/physical-network.js", "js/studio-examples.js" ] } }, { "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: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: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:busbar", "type": "Term", "label": "Busbar", "properties": { "id": "busbar", "name": "Busbar", "section": "topic-pack", "definition": "A rigid copper or aluminium conductor that joins cell terminals into series and parallel groups, and modules into the pack. Its cross-section is sized for current and heating, and its joints — welded or bolted — are a classic source of resistance and failure.", "related": [ "series-parallel", "terminal", "laser-welding", "internal-resistance", "wire-bonding" ], "url": "https://lemonergy.com/learn/glossary/busbar/", "mentions": [] } }, { "id": "term:open-circuit-voltage", "type": "Term", "label": "Open-circuit voltage", "properties": { "id": "open-circuit-voltage", "name": "Open-circuit voltage", "abbr": "OCV", "section": "topic-state", "definition": "The voltage across a cell’s terminals when no current flows and the cell has rested long enough for the voltage to settle. It depends on state of charge and temperature, and a cell whose open-circuit voltage falls unusually fast in storage may have an internal short.", "unit": "V", "related": [ "ocv-soc-curve", "relaxation", "voltage-hysteresis", "k-value", "internal-short-circuit" ], "lesson": "fundamentals/cell-production/#finishing", "url": "https://lemonergy.com/learn/glossary/open-circuit-voltage/", "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: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": "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" } } ] }