{ "node": { "id": "term:fuel-gauge", "type": "Term", "label": "Fuel gauge", "properties": { "id": "fuel-gauge", "name": "Fuel gauge", "aka": [ "gas gauge" ], "section": "topic-pack", "definition": "The single chip in a phone, laptop or power tool that does the BMS’s state-estimation job for one or a few cells: coulomb counting corrected by an OCV model, with impedance tracking in better parts. It reports remaining capacity over SMBus or I²C.", "related": [ "coulomb-counting", "state-of-charge", "smbus", "consumer-electronics", "afe" ], "url": "https://lemonergy.com/learn/glossary/fuel-gauge/", "mentions": [ "coulomb", "impedance", "open-circuit-voltage", "bms" ] } }, "edges": [ { "id": "edge:3037", "source": "term:fuel-gauge", "target": "topic:topic-pack", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:3038", "source": "term:fuel-gauge", "target": "term:coulomb-counting", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:3039", "source": "term:fuel-gauge", "target": "term:state-of-charge", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:3040", "source": "term:fuel-gauge", "target": "term:smbus", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:3041", "source": "term:fuel-gauge", "target": "term:consumer-electronics", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:3042", "source": "term:fuel-gauge", "target": "term:afe", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/fuel-gauge/coulomb", "source": "term:fuel-gauge", "target": "term:coulomb", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:mentions/fuel-gauge/impedance", "source": "term:fuel-gauge", "target": "term:impedance", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:mentions/fuel-gauge/open-circuit-voltage", "source": "term:fuel-gauge", "target": "term:open-circuit-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/fuel-gauge/bms", "source": "term:fuel-gauge", "target": "term:bms", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:3047", "source": "term:fuel-gauge", "target": "visual:soc", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } } ], "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:coulomb-counting", "type": "Term", "label": "Coulomb counting", "properties": { "id": "coulomb-counting", "name": "Coulomb counting", "aka": [ "ampere-hour counting" ], "section": "topic-state", "definition": "Estimating state of charge by integrating the measured current over time. Simple and fast, but sensor offset accumulates, so it is corrected against the OCV–SOC curve at rest or fused with it in a Kalman filter.", "formula": "SOC(t) = SOC₀ − ∫ I dt / Q", "related": [ "state-of-charge", "ocv-soc-curve", "kalman-filter", "current-sensor" ], "example": { "title": "Integrate a discharge step", "text": "Starting at 80% SOC with a 5 Ah available capacity, an ideal 2 A discharge for 30 min removes 1 Ah and lowers SOC to 60%. This example takes discharge current as positive and ignores efficiency and sensor error." }, "url": "https://lemonergy.com/learn/glossary/coulomb-counting/", "mentions": [ "open-circuit-voltage" ] } }, { "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. 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The Smart Battery Data specification defines the register set, so any compliant charger can read it.", "related": [ "bms", "fuel-gauge", "consumer-electronics", "charger" ], "url": "https://lemonergy.com/learn/glossary/smbus/", "mentions": [] } }, { "id": "term:consumer-electronics", "type": "Term", "label": "Consumer electronics", "properties": { "id": "consumer-electronics", "name": "Consumer electronics", "section": "topic-applications", "definition": "Phones, laptops, wearables and tools: the first mass market for lithium-ion and still the one that pays for the highest energy density. It favours pouch cells with LCO or high-nickel positives and silicon-blended negatives.", "related": [ "lco", "pouch-cell", "fuel-gauge", "smbus", "iec-62133" ], "url": "https://lemonergy.com/learn/glossary/consumer-electronics/", "mentions": [ "energy-density" ] } }, { "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:coulomb", "type": "Term", "label": "Coulomb", "properties": { "id": "coulomb", "name": "Coulomb", "abbr": "C", "section": "topic-units", "definition": "The SI unit of electric charge; one ampere flowing for one second. Battery engineers prefer the ampere-hour, which is 3600 coulombs, because cells deliver their charge over hours.", "unit": "C", "related": [ "ampere-hour", "faradays-constant" ], "url": "https://lemonergy.com/learn/glossary/coulomb/", "mentions": [ "ampere", "electric-charge" ] } }, { "id": "term:impedance", "type": "Term", "label": "Impedance", "properties": { "id": "impedance", "name": "Impedance", "abbr": "Z", "section": "topic-units", "definition": "The frequency-dependent generalisation of resistance, with a magnitude and a phase. A cell’s impedance separates ohmic, charge-transfer and diffusion contributions that a single DC resistance lumps together.", "unit": "Ω", "related": [ "internal-resistance", "electrochemical-impedance-spectroscopy", "nyquist-plot" ], "url": "https://lemonergy.com/learn/glossary/impedance/", "mentions": [ "diffusion" ] } }, { "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: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": "visual:soc", "type": "Visual", "label": "Charge balance and state of charge", "properties": { "title": "Charge balance and state of charge", "summary": "SOC rises with accumulated charge; depth of discharge falls by the same amount.", "readout": "From 20% SOC, ideal full charge takes 48 min. Integration stops at 100%.", "formula": "SOC = SOC₀ + ∫ I_charge dt / Q; DOD = 1 − SOC", "note": "Current is positive into the cell. Constant capacity and 100% charge efficiency; no CC-CV taper.", "software": { "status": "studio", "label": "Charge balance in Studio", "body": "Battery state advances by integrating current over each time step. This illustration assumes fixed capacity and 100% charge efficiency; it does not implement an estimator or correct sensor drift.", "href": "https://design.lemonergy.com/cosim.html?example=charging-home" }, "html": "
Complementary charge fractions
Complementary charge fractionsTime (h) versus Capacity fraction (%). SOC; DOD. Interpretation follows the graphs.002515027531004Time (h)Capacity fraction (%)
SOCDOD (dashed)
" } } ] }