{ "node": { "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" ] } }, "edges": [ { "id": "edge:154", "source": "term:ohms-law", "target": "workflow:ohm-circuit", "type": "usedIn", "properties": { "sourceFile": "wiki-blocks.json" } }, { "id": "edge:273", "source": "term:ohms-law", "target": "topic:topic-units", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:274", "source": "term:ohms-law", "target": "term:internal-resistance", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:275", "source": "term:ohms-law", "target": "term:ir-drop", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:276", "source": "term:ohms-law", "target": "term:ohm", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:277", "source": "term:ohms-law", "target": "term:kirchhoffs-laws", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/ohms-law/voltage", "source": "term:ohms-law", "target": "term:voltage", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:279", "source": "term:ohms-law", "target": "visual:voltage", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } } ], "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-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: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" ] } }, { "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:ohm", "type": "Term", "label": "Ohm", "properties": { "id": "ohm", "name": "Ohm", "abbr": "Ω", "section": "topic-units", "definition": "The SI unit of electrical resistance: one volt per ampere. Cell internal resistance is about a milliohm for a large automotive cell and tens of milliohms for a small cylindrical one.", "unit": "Ω", "related": [ "internal-resistance", "ohms-law", "impedance" ], "url": "https://lemonergy.com/learn/glossary/ohm/", "mentions": [ "ampere", "volt" ] } }, { "id": "term:kirchhoffs-laws", "type": "Term", "label": "Kirchhoff’s laws", "properties": { "id": "kirchhoffs-laws", "name": "Kirchhoff’s laws", "aka": [ "Kirchhoff’s current law", "Kirchhoff’s voltage law", "KCL", "KVL" ], "section": "topic-units", "definition": "Two rules of circuit analysis: the currents flowing into any node sum to zero, and the voltages around any closed loop sum to zero. In a pack they explain why every cell in a series string carries the same current, and why cells in a parallel group share current unequally when their resistances differ.", "formula": "ΣI = 0 at a node; ΣV = 0 around a loop", "related": [ "series-parallel", "ohms-law", "current", "voltage", "internal-resistance", "cell-to-cell-variation" ], "example": { "title": "Balance a parallel junction", "text": "If 6 A enters a junction and 2 A leaves through one branch, 4 A must leave through the other branch in a steady circuit. Voltage differences around a closed loop must also sum to zero." }, "url": "https://lemonergy.com/learn/glossary/kirchhoffs-laws/", "mentions": [ "string" ] } }, { "id": "term:voltage", "type": "Term", "label": "Voltage", "properties": { "id": "voltage", "name": "Voltage", "aka": [ "terminal voltage" ], "section": "topic-units", "definition": "The potential difference between a cell’s two terminals. It comes from the chemical difference between the electrodes, moves with state of charge, and sags under load because of internal resistance.", "unit": "V", "related": [ "open-circuit-voltage", "nominal-voltage", "internal-resistance", "ir-drop" ], "lesson": "fundamentals/cell-anatomy/#voltage", "url": "https://lemonergy.com/learn/glossary/voltage/", "mentions": [ "state-of-charge" ] } }, { "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)
" } } ] }