Battery knowledge · Applications and market
Road-load power demand
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.
- Also called
- road load, tractive power, traction power demand
- Unit
- W
- Relationship
- P = v·(½·ρ·C_d·A·v² + C_rr·m·g·cos θ + m·g·sin θ + m·a)
Example
Isolate the aerodynamic contribution
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.
Explore the graph
Separate steady rolling resistance from aerodynamic drag on a flat road.
At 100 km/h, wheel power is 12.78 kW: 7.877 kW drag and 4.903 kW rolling resistance.
P_wheel = v [½ρ(CdA)v² + Crr m g] for flat road and constant speed
Illustrative model. Air density 1.225 kg/m³, rolling coefficient 0.01, no wind, road gradient or acceleration. Drivetrain losses and auxiliary loads are excluded.
Use in Lemonergy
Design protocol or analysis tool
Replay a changing load
Replay applies an existing governed profile.
Equation or tool to use
- Dynamic profile
Replays selected power
Inputs & settings
- profileId
- passes
- scaleW
- Rest
Observes recovery
Inputs & settings
- s
This overview identifies the components to use. Follow the example in Lemonergy for their connections and settings.
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.
The selected profile determines regeneration. This is not an independent road-load or motor-efficiency model.
Open Design → Protocol bench →References & further reading
Further reading on this topic
These sources provide broader context; they are not presented as citations for every statement in this entry.
- DOE/EPRI 2013 Electricity Storage Handbook in Collaboration with NRECA
Sandia National Laboratories · 2013
Topic background · Storage technologies and grid services. The publisher notes that its historical cost and deployment figures are outdated.