{ "node": { "id": "term:road-load-power", "type": "Term", "label": "Road-load power demand", "properties": { "id": "road-load-power", "name": "Road-load power demand", "aka": [ "road load", "tractive power", "traction power demand" ], "section": "topic-applications", "definition": "The power a vehicle needs at its wheels to overcome aerodynamic drag, rolling resistance, gradient and inertia at a given moment. Drag power rises with the cube of speed, which is why motorway driving drains a battery so much faster than town driving; integrated over a drive cycle it gives energy consumption and range.", "formula": "P = v·(½·ρ·C_d·A·v² + C_rr·m·g·cos θ + m·g·sin θ + m·a)", "unit": "W", "related": [ "range", "load-profile", "regenerative-braking", "traction-motor", "power" ], "example": { "title": "Isolate the aerodynamic contribution", "text": "Using illustrative ρ = 1.2 kg/m³, drag coefficient 0.30, frontal area 2.2 m² and speed 20 m/s, aerodynamic power alone is about 3.17 kW. Rolling resistance, grade, acceleration and drivetrain losses add to it." }, "url": "https://lemonergy.com/learn/glossary/road-load-power/", "mentions": [] } }, "edges": [ { "id": "edge:147", "source": "term:road-load-power", "target": "workflow:drive-profile", "type": "usedIn", "properties": { "sourceFile": "wiki-blocks.json" } }, { "id": "edge:6914", "source": "term:road-load-power", "target": "topic:topic-applications", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:6915", "source": "term:road-load-power", "target": "term:range", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:6916", "source": "term:road-load-power", "target": "term:load-profile", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:6917", "source": "term:road-load-power", "target": "term:regenerative-braking", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:6918", "source": "term:road-load-power", "target": "term:traction-motor", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:6919", "source": "term:road-load-power", "target": "term:power", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:6920", "source": "term:road-load-power", "target": "visual:road-load", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } } ], "neighbors": [ { "id": "workflow:drive-profile", "type": "Workflow", "label": "Replay a changing load", "properties": { "id": "drive-profile", "title": "Replay a changing load", "kind": "protocol", "summary": "Replay applies an existing governed profile.", "steps": [ "Open Drive-cycle replay.", "Inspect profile and scale; compare current and SOC." ], "example": "40 kW at 400 V needs about 100 A before losses; at 350 V it needs about 114 A.", "observe": "Current rises as voltage falls under fixed power.", "limits": "The selected profile determines regeneration. This is not an independent road-load or motor-efficiency model.", "url": "https://design.lemonergy.com/", "label": "Open Design → Protocol bench", "evidence": [ "js/test-protocol.js" ] } }, { "id": "topic:topic-applications", "type": "Topic", "label": "Applications and market", "properties": { "id": "topic-applications", "name": "Applications and market", "lede": "Where batteries are used, and the terms used to buy, size and compare them.", "context": "Start with mission energy, peak power and operating conditions.", "example": "20 kWh total energy and a ten-second 100 kW peak constrain different design aspects.", "lesson_url": "https://lemonergy.com/learn/fundamentals/capacity-and-c-rate/", "lesson_label": "Open energy and power" } }, { "id": "term:range", "type": "Term", "label": "Range", "properties": { "id": "range", "name": "Range", "section": "topic-applications", "definition": "How far an electric vehicle travels on a full charge: usable energy divided by consumption per kilometre. Cold weather, speed and heating cut it, and the gap between official and real range is usually consumption, not battery capacity.", "unit": "km", "related": [ "usable-capacity", "state-of-energy", "electric-vehicle", "energy-density", "energy-consumption-per-distance", "road-load-power" ], "url": "https://lemonergy.com/learn/glossary/range/", "mentions": [] } }, { "id": "term:load-profile", "type": "Term", "label": "Load profile", "properties": { "id": "load-profile", "name": "Load profile", "aka": [ "duty cycle", "drive cycle" ], "section": "topic-charging", "definition": "The current or power a battery must deliver as a function of time in its application — a drive cycle for a car, a daily charge–discharge pattern for storage. Aging tests built on a realistic profile predict life better than constant-current cycling.", "related": [ "cycle", "depth-of-discharge", "cycle-aging", "regenerative-braking", "load" ], "url": "https://lemonergy.com/learn/glossary/load-profile/", "mentions": [] } }, { "id": "term:regenerative-braking", "type": "Term", "label": "Regenerative braking", "properties": { "id": "regenerative-braking", "name": "Regenerative braking", "section": "topic-charging", "definition": "Using a vehicle’s motor as a generator while slowing down, so braking energy charges the battery in short high-current pulses. A cold or full battery cannot accept it, which is one reason a BMS computes charge power limits continuously.", "related": [ "state-of-power", "fast-charging", "electric-vehicle", "load-profile" ], "url": "https://lemonergy.com/learn/glossary/regenerative-braking/", "mentions": [ "bms" ] } }, { "id": "term:traction-motor", "type": "Term", "label": "Traction motor", "properties": { "id": "traction-motor", "name": "Traction motor", "aka": [ "e-motor", "electric machine", "drive motor" ], "section": "topic-applications", "definition": "The electric machine that drives a vehicle’s wheels, fed by the inverter from the battery and run as a generator during regenerative braking. Most are permanent-magnet synchronous motors with neodymium magnets; induction and wound-rotor machines avoid rare earths. Its peak power, often 100–300 kW in a car, sets the discharge power the pack must supply.", "related": [ "inverter", "regenerative-braking", "state-of-power", "electric-vehicle", "specific-power" ], "url": "https://lemonergy.com/learn/glossary/traction-motor/", "mentions": [] } }, { "id": "term:power", "type": "Term", "label": "Power", "properties": { "id": "power", "name": "Power", "section": "topic-units", "definition": "The rate at which a cell delivers or absorbs energy: voltage times current, in watts. Power is limited by internal resistance and temperature long before capacity runs out.", "formula": "P = V × I", "unit": "W", "related": [ "watt", "specific-power", "state-of-power", "internal-resistance" ], "example": { "title": "Separate power from energy", "text": "A 100 W load running for 30 min uses 50 Wh. Power tells you how fast energy is transferred; the duration determines how much energy is transferred." }, "url": "https://lemonergy.com/learn/glossary/power/", "mentions": [] } }, { "id": "visual:road-load", "type": "Visual", "label": "Aerodynamic power rises with speed cubed", "properties": { "title": "Aerodynamic power rises with speed cubed", "summary": "Separate steady rolling resistance from aerodynamic drag on a flat road.", "readout": "At 100 km/h, wheel power is 12.78 kW: 7.877 kW drag and 4.903 kW rolling resistance.", "formula": "P_wheel = v [½ρ(CdA)v² + Crr m g] for flat road and constant speed", "note": "Air density 1.225 kg/m³, rolling coefficient 0.01, no wind, road gradient or acceleration. Drivetrain losses and auxiliary loads are excluded.", "software": { "status": "reference", "label": "Reference concept", "body": "This analytical road-load example is a reference calculation. It does not execute the product vehicle model or predict battery-side consumption over a drive cycle.", "href": "../chapter-1/" }, "html": "
Steady wheel power
Steady wheel powerVehicle speed (km/h) versus Wheel power (kW). Total; Aerodynamic drag; Rolling resistance. Interpretation follows the graphs.005.9232.511.86517.897.523.7130Vehicle speed (km/h)Wheel power (kW)
TotalAerodynamic drag (dashed)Rolling resistance
" } } ] }