{ "node": { "id": "term:internal-resistance", "type": "Term", "label": "Internal resistance", "properties": { "id": "internal-resistance", "name": "Internal resistance", "abbr": "IR", "aka": [ "DC resistance", "DCIR" ], "section": "topic-units", "definition": "The resistance a cell presents to current, from its foils, electrolyte, interfaces and the reactions themselves. It converts part of the delivered energy into heat, sets the voltage drop under load, and rises as the cell ages; a large automotive cell has about a milliohm, a small cylindrical cell tens.", "unit": "mΩ", "related": [ "ohms-law", "ir-drop", "impedance-rise", "dcir", "area-specific-resistance", "resistance-capacity-product" ], "lesson": "fundamentals/battery-basics/#datasheet", "url": "https://lemonergy.com/learn/glossary/internal-resistance/", "mentions": [ "electrolyte", "cylindrical-cell" ] } }, "edges": [ { "id": "edge:50", "source": "term:internal-resistance", "target": "workflow:ocv-charge-balance", "type": "usedIn", "properties": { "sourceFile": "wiki-blocks.json" } }, { "id": "edge:280", "source": "term:internal-resistance", "target": "topic:topic-units", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:281", "source": "term:internal-resistance", "target": "term:ohms-law", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:282", "source": "term:internal-resistance", "target": "term:ir-drop", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:283", "source": "term:internal-resistance", "target": "term:impedance-rise", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:284", "source": "term:internal-resistance", "target": "term:dcir", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:285", "source": "term:internal-resistance", "target": "term:area-specific-resistance", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:286", "source": "term:internal-resistance", "target": "term:resistance-capacity-product", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/internal-resistance/electrolyte", "source": "term:internal-resistance", "target": "term:electrolyte", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:mentions/internal-resistance/cylindrical-cell", "source": "term:internal-resistance", "target": "term:cylindrical-cell", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:289", "source": "term:internal-resistance", "target": "lesson:fundamentals/battery-basics/", "type": "explainedIn", "properties": { "sourceFile": "terms.json", "url": "https://lemonergy.com/learn/fundamentals/battery-basics/#datasheet" } }, { "id": "edge:290", "source": "term:internal-resistance", "target": "visual:voltage", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } }, { "id": "edge:291", "source": "term:internal-resistance", "target": "reference:plett-modeling", "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-units", "type": "Topic", "label": "Units and electrical basics", "properties": { "id": "topic-units", "name": "Units and electrical basics", "lede": "The quantities every datasheet is written in, and how they relate.", "context": "Use consistent units and cell/pack basis.", "example": "10 A for 30 min transfers 5 Ah. At constant 3.6 V this is 18 Wh; varying voltage requires integration.", "lesson_url": "https://lemonergy.com/learn/fundamentals/capacity-and-c-rate/", "lesson_label": "Open capacity and C-rate" } }, { "id": "term:ohms-law", "type": "Term", "label": "Ohm’s law", "properties": { "id": "ohms-law", "name": "Ohm’s law", "section": "topic-units", "definition": "Voltage across a resistance equals current times that resistance. Applied to a cell it predicts the voltage drop under load from the internal resistance, which is the first-order reason terminal voltage sags.", "formula": "V = I × R", "related": [ "internal-resistance", "ir-drop", "ohm", "kirchhoffs-laws" ], "example": { "title": "Convert a resistance into a voltage drop", "text": "A 10 A current through a 20 mΩ resistance produces 0.2 V of voltage drop. Use 0.020 Ω in V = IR; inserting the number 20 without converting milliohms would be wrong." }, "url": "https://lemonergy.com/learn/glossary/ohms-law/", "mentions": [ "voltage" ] } }, { "id": "term:ir-drop", "type": "Term", "label": "IR drop", "properties": { "id": "ir-drop", "name": "IR drop", "aka": [ "ohmic drop", "voltage sag" ], "section": "topic-charging", "definition": "The instant step in terminal voltage when current starts or stops, equal to current times internal resistance. It is lost as heat and is the reason a cell’s voltage under load sits below its open-circuit voltage.", "formula": "ΔV = I × R", "unit": "V", "related": [ "internal-resistance", "ohms-law", "polarization", "open-circuit-voltage" ], "example": { "title": "Distinguish a current step from SOC change", "text": "When discharge current jumps from 0 A to 10 A through an illustrative 20 mΩ resistance, terminal voltage immediately drops by 0.2 V. Slower polarization and SOC change are separate effects." }, "url": "https://lemonergy.com/learn/glossary/ir-drop/", "mentions": [ "voltage", "closed-circuit-voltage" ] } }, { "id": "term:impedance-rise", "type": "Term", "label": "Impedance rise", "properties": { "id": "impedance-rise", "name": "Impedance rise", "aka": [ "resistance growth", "power fade" ], "section": "topic-aging", "definition": "An increase in a cell’s internal resistance as it ages. It costs voltage under load and therefore power, even while the stored charge is still there.", "related": [ "internal-resistance", "sei", "cei", "state-of-power", "state-of-health" ], "lesson": "fundamentals/battery-aging/#crystals", "url": "https://lemonergy.com/learn/glossary/impedance-rise/", "mentions": [ "closed-circuit-voltage" ] } }, { "id": "term:dcir", "type": "Term", "label": "DC internal resistance", "properties": { "id": "dcir", "name": "DC internal resistance", "abbr": "DCIR", "aka": [ "DC-IR", "pulse resistance" ], "section": "topic-testing", "definition": "Internal resistance measured from the voltage change during a current pulse of defined length, usually 10 s or 18 s. It is larger than the AC value because it includes charge-transfer and some diffusion, and it depends on SOC, temperature and pulse duration.", "unit": "mΩ", "related": [ "internal-resistance", "acir", "hppc", "impedance-rise" ], "url": "https://lemonergy.com/learn/glossary/dcir/", "mentions": [ "state-of-charge", "diffusion" ] } }, { "id": "term:area-specific-resistance", "type": "Term", "label": "Area-specific resistance", "properties": { "id": "area-specific-resistance", "name": "Area-specific resistance", "abbr": "ASR", "aka": [ "area-specific impedance", "ASI" ], "section": "topic-electrochemistry", "definition": "A cell’s or layer’s resistance multiplied by its electrode area, which makes resistance comparable between cells of any size. A 100 Ah cell with 2.5 m² of electrode area and 1 mΩ of resistance has an ASR of 25 Ω·cm²; cell designers and solid-state interface researchers both work in it.", "formula": "ASR = R · A", "unit": "Ω·cm²", "related": [ "internal-resistance", "areal-loading", "dcir", "impedance", "solid-electrolyte" ], "example": { "title": "Normalize by active area", "text": "An illustrative measured resistance of 0.2 Ω across 5 cm² corresponds to 1 Ω·cm². Use the same geometrical-area convention when comparing samples." }, "url": "https://lemonergy.com/learn/glossary/area-specific-resistance/", "mentions": [ "electrode" ] } }, { "id": "term:resistance-capacity-product", "type": "Term", "label": "Resistance–capacity product", "properties": { "id": "resistance-capacity-product", "name": "Resistance–capacity product", "aka": [ "ohm-ampere-hour", "mΩ·Ah", "siemens per watt-hour", "S/Wh" ], "section": "topic-ratings", "definition": "A cell’s internal resistance multiplied by its capacity, which cancels out size: ten 5 Ah, 20 mΩ cells in parallel make 50 Ah at 2 mΩ, both 100 mΩ·Ah. Lower values mean more power per unit of stored energy. Conductance divided by energy, in siemens per watt-hour, expresses the same figure of merit the other way up.", "formula": "R·Q (mΩ·Ah); G/E = 1/(R·E) (S/Wh)", "unit": "mΩ·Ah", "related": [ "internal-resistance", "power-cell-energy-cell", "specific-power", "nominal-capacity", "siemens", "dcir" ], "example": { "title": "Compare two cell sizes", "text": "A 5 Ah cell with 20 mΩ resistance and a 10 Ah cell with 10 mΩ resistance both have RQ = 100 mΩ·Ah. Compare like test conditions; identical RQ does not imply identical chemistry or thermal behavior." }, "url": "https://lemonergy.com/learn/glossary/resistance-capacity-product/", "mentions": [ "watt-hour" ] } }, { "id": "term:electrolyte", "type": "Term", "label": "Electrolyte", "properties": { "id": "electrolyte", "name": "Electrolyte", "section": "topic-electrolytes", "definition": "The ion-conducting medium between the electrodes. In a liquid-electrolyte cell it fills the pores of both electrodes and the separator, so it is not a separate structural layer.", "related": [ "lithium-salt", "carbonate-solvent", "electrolyte-additive", "ionic-conductivity", "solid-electrolyte", "ionic-liquid-electrolyte" ], "lesson": "fundamentals/cell-architecture/#electrolyte", "example": { "title": "Ions and electrons", "text": "Electrolyte carries ions between electrodes; the external circuit carries electrons. The two paths serve different roles." }, "url": "https://lemonergy.com/learn/glossary/electrolyte/", "mentions": [ "separator" ] } }, { "id": "term:cylindrical-cell", "type": "Term", "label": "Cylindrical cell", "properties": { "id": "cylindrical-cell", "name": "Cylindrical cell", "aka": [ "18650", "21700", "4680" ], "section": "topic-chemistries", "definition": "A cell made by winding the electrodes into a jelly roll and sealing it in a round metal can. Sizes are named by their dimensions: a 21700 cell is 21 mm across and 70 mm long.", "related": [ "jelly-roll", "can", "tabless-design", "prismatic-cell", "pouch-cell", "centre-pin" ], "lesson": "fundamentals/cell-production/#formats", "example": { "title": "Shape versus ratings", "text": "A cylindrical shape does not supply the model’s capacity, resistance or voltage limits; those belong to the actual cell." }, "url": "https://lemonergy.com/learn/glossary/cylindrical-cell/", "mentions": [ "winding" ] } }, { "id": "lesson:fundamentals/battery-basics/", "type": "Lesson", "label": "Lesson 0 · Battery basics", "properties": { "url": "https://lemonergy.com/learn/fundamentals/battery-basics/" } }, { "id": "visual:voltage", "type": "Visual", "label": "Voltage under load", "properties": { "title": "Voltage under load", "summary": "Discharge current creates an ohmic drop below open-circuit voltage.", "readout": "5 A through 20 mΩ gives 0.1 V ohmic drop.", "formula": "V_terminal = OCV − I_discharge R", "note": "Chosen OCV curve; no chemistry calibration, hysteresis or voltage cutoff.", "software": { "status": "studio", "label": "Voltage relationship in Studio", "body": "The native battery calculates terminal voltage from OCV and resistance. The curve here is an illustrative OCV relationship, not a fitted cell dataset.", "href": "https://design.lemonergy.com/cosim.html?example=charging-home" }, "html": "
Illustrative OCV and loaded voltage
Illustrative OCV and loaded voltageSOC (%) versus Voltage (V). Open circuit; Under load. Interpretation follows the graphs.1.802.42253.05503.67754.3100SOC (%)Voltage (V)
Open circuitUnder load (dashed)
" } }, { "id": "reference:plett-modeling", "type": "Reference", "label": "Extended Kalman filtering for battery management systems of LiPB-based HEV battery packs: Part 2. Modeling and identification", "properties": { "title": "Extended Kalman filtering for battery management systems of LiPB-based HEV battery packs: Part 2. Modeling and identification", "publisher": "Journal of Power Sources", "url": "https://doi.org/10.1016/j.jpowsour.2004.02.032", "type": "Research article", "scope": "Battery charge balance, open-circuit voltage, ohmic loss, polarization dynamics and model identification; parameters require cell-specific data.", "year": 2004, "authors": [ "Gregory L. Plett" ], "accessed": "2026-10-27" } } ] }