{ "node": { "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" ] } }, "edges": [ { "id": "edge:43", "source": "term:state-of-charge", "target": "workflow:ocv-charge-balance", "type": "usedIn", "properties": { "sourceFile": "wiki-blocks.json" } }, { "id": "edge:1220", "source": "term:state-of-charge", "target": "topic:topic-state", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:1221", "source": "term:state-of-charge", "target": "term:depth-of-discharge", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:1222", "source": "term:state-of-charge", "target": "term:ocv-soc-curve", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:1223", "source": "term:state-of-charge", "target": "term:coulomb-counting", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:1224", "source": "term:state-of-charge", "target": "term:state-of-health", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:1225", "source": "term:state-of-charge", "target": "term:bms", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/state-of-charge/usable-capacity", "source": "term:state-of-charge", "target": "term:usable-capacity", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:1227", "source": "term:state-of-charge", "target": "lesson:fundamentals/battery-aging/", "type": "explainedIn", "properties": { "sourceFile": "terms.json", "url": "https://lemonergy.com/learn/fundamentals/battery-aging/#storage-soc" } }, { "id": "edge:1228", "source": "term:state-of-charge", "target": "visual:soc", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } }, { "id": "edge:1229", "source": "term:state-of-charge", "target": "reference:plett-estimation", "type": "cites", "properties": { "sourceFile": "wiki-references.json", "scope": "direct technical reference" } } ], "neighbors": [ { "id": "workflow:ocv-charge-balance", "type": "Workflow", "label": "Connect SOC and voltage", "properties": { "id": "ocv-charge-balance", "title": "Connect SOC and voltage", "kind": "studio", "summary": "The battery integrates charge and combines OCV with resistance.", "steps": [ "Inspect capacity, initial SOC and OCV endpoints.", "Compare OCV with terminal voltage." ], "example": "OCV endpoints of 300 and 420 V give 360 V at 50% SOC. Charging at 10 A through 0.08 Ω adds 0.8 V.", "observe": "At unity coulombic efficiency, 10 A for 1 h adds ten percentage points to 100 Ah.", "limits": "Internal model SOC is not an estimate of an unknown physical battery. OCV is linear and resistance fixed.", "url": "https://design.lemonergy.com/cosim.html?example=charging-home", "label": "Open the Studio example", "evidence": [ "js/charging-control.js", "js/charging-scenarios.js", "docs/CHARGING_BLOCKS_SPEC.md" ] } }, { "id": "topic:topic-state", "type": "Topic", "label": "State estimation", "properties": { "id": "topic-state", "name": "State estimation", "lede": "The quantities a battery management system estimates but cannot measure directly.", "context": "Distinguish internal states from noisy measurement estimates.", "example": "Current-sensor bias accumulates in coulomb counting. Exact model SOC does not establish real estimator accuracy.", "lesson_url": "https://lemonergy.com/learn/fundamentals/capacity-and-c-rate/", "lesson_label": "Open charge balance" } }, { "id": "term:depth-of-discharge", "type": "Term", "label": "Depth of discharge", "properties": { "id": "depth-of-discharge", "name": "Depth of discharge", "abbr": "DOD", "section": "topic-state", "definition": "How much of a cell’s capacity is used in a cycle. Deep cycles cause more mechanical stress in the active materials than shallow ones.", "unit": "%", "related": [ "state-of-charge", "cycle-life", "particle-cracking", "usable-capacity" ], "lesson": "fundamentals/battery-aging/#cracking", "url": "https://lemonergy.com/learn/glossary/depth-of-discharge/", "mentions": [] } }, { "id": "term:ocv-soc-curve", "type": "Term", "label": "OCV–SOC curve", "properties": { "id": "ocv-soc-curve", "name": "OCV–SOC curve", "section": "topic-state", "definition": "The characteristic relation between a cell’s open-circuit voltage and its state of charge, measured once at low current and stored in the BMS. A steep curve, as for NMC, makes SOC easy to read from voltage; LFP’s flat curve does not.", "related": [ "open-circuit-voltage", "state-of-charge", "coulomb-counting", "lfp", "voltage-plateau", "ocv-test" ], "url": "https://lemonergy.com/learn/glossary/ocv-soc-curve/", "mentions": [ "bms" ] } }, { "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-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: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:usable-capacity", "type": "Term", "label": "Usable capacity", "properties": { "id": "usable-capacity", "name": "Usable capacity", "aka": [ "available capacity" ], "section": "topic-ratings", "definition": "The part of a cell’s capacity that a system actually lets it use, after the BMS reserves margins at the top and bottom of the state-of-charge window. An electric-car pack may use 90–95 % of its gross capacity.", "related": [ "nominal-capacity", "depth-of-discharge", "state-of-charge", "bms" ], "url": "https://lemonergy.com/learn/glossary/usable-capacity/", "mentions": [] } }, { "id": "lesson:fundamentals/battery-aging/", "type": "Lesson", "label": "Lesson 4 · Battery aging", "properties": { "url": "https://lemonergy.com/learn/fundamentals/battery-aging/" } }, { "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)
" } }, { "id": "reference:plett-estimation", "type": "Reference", "label": "Extended Kalman filtering for battery management systems of LiPB-based HEV battery packs: Part 3. State and parameter estimation", "properties": { "title": "Extended Kalman filtering for battery management systems of LiPB-based HEV battery packs: Part 3. State and parameter estimation", "publisher": "Journal of Power Sources", "url": "https://doi.org/10.1016/j.jpowsour.2004.02.033", "type": "Research article", "scope": "Model-based battery state-of-charge and parameter estimation with extended Kalman filtering, including uncertainty and model dependence.", "year": 2004, "authors": [ "Gregory L. Plett" ], "accessed": "2026-10-27" } } ] }