Calculator
Example Data Table
| Vehicle type | Mass kg | Payload kg | Crr | Speed km/h | Grade % | Voltage V |
|---|---|---|---|---|---|---|
| Small electric car | 1450 | 180 | 0.012 | 80 | 0 | 400 |
| Delivery van | 2600 | 650 | 0.015 | 65 | 2 | 520 |
| Utility cart | 650 | 250 | 0.025 | 25 | 4 | 72 |
Formula Used
Total mass: m = vehicle mass + payload mass
Effective coefficient: Crr effective = base Crr × surface factor × pressure factor × temperature factor
Rolling resistance: Frr = Crr effective × m × g × cos(theta)
Grade force: Fgrade = m × g × sin(theta)
Aerodynamic force: Faero = 0.5 × air density × Cd × frontal area × relative air speed²
Wheel power: Pwheel = total road force × vehicle speed
Battery power: Pbattery = positive wheel power ÷ drivetrain efficiency + auxiliary load
Current: I = Pbattery ÷ bus voltage
How to Use This Calculator
Enter the vehicle mass and payload first. Add the rolling coefficient for the tire and road condition. Use 0.010 to 0.015 for many passenger tires on good pavement. Use higher values for rough surfaces.
Next, enter tire pressure, road grade, speed, route distance, drivetrain efficiency, bus voltage, and auxiliary load. Enable aerodynamic drag when highway speed or headwind matters. Press Calculate to view force, power, current, and energy. Use CSV or PDF buttons to save the same calculated report.
Vehicle Rolling Resistance and Electrical Demand
Understanding rolling resistance
Rolling resistance is the force that appears when tires deform under load. It is small compared with a hard climb, yet it never disappears while the vehicle moves. For electric vehicles, this force is important because it converts battery energy into heat inside the tires and road contact patch.
Why the result matters
A lower rolling force reduces wheel power at every steady speed. It also reduces current draw from the battery. That can improve range, reduce motor heating, and support better cable, fuse, and controller selection. Heavy payloads, low tire pressure, cold tires, and rough surfaces all raise the coefficient. A small coefficient change can become large on long routes.
Electrical view
The calculator links mechanical road load with electrical demand. It first finds normal force from total mass and road grade. It then multiplies that force by the effective rolling coefficient. Wheel power is force times speed. Battery power is higher than wheel power because the drivetrain has losses. The tool also adds auxiliary power, so lights, pumps, fans, and electronics are not ignored.
Advanced planning
The grade input helps compare flat roads with climbs. A positive grade adds tractive force. A negative grade may create regeneration potential. The optional aerodynamic section is useful when speed is high. At city speeds, tires and mass may dominate. At highway speeds, drag can exceed rolling load.
Practical interpretation
Use realistic values rather than perfect laboratory numbers. Passenger tires often use a coefficient near 0.010 to 0.015 on good pavement. Efficient tires may be lower. Off road tires, gravel, and soft ground can be much higher. Tire pressure affects the answer, so compare actual pressure with the recommended value. Cold weather can also increase losses.
Design use
Use the current result to check battery discharge, motor controller limits, and conductor sizing. Use energy per kilometer to estimate route consumption. Use rolling equivalent grade to explain the tire loss as a hill-like load. Recalculate after changing payload, speed, tire pressure, or surface. This makes the calculator useful for vehicle audits, conversions, delivery routes, and electric drivetrain studies. Keep one record for each route. Compare reports to see which change gives the best energy saving before spending money.
FAQs
What is rolling resistance?
Rolling resistance is the opposing force caused mainly by tire deformation, road contact, and material losses. It acts against motion whenever the vehicle rolls.
Why is this useful for electric vehicles?
It converts tire force into wheel power, battery power, current, and trip energy. These values help with range checks and electrical component sizing.
What Crr value should I enter?
Use tire test data when available. For many passenger tires on good pavement, 0.010 to 0.015 is a practical starting range.
Does tire pressure affect the result?
Yes. Lower tire pressure usually increases tire deformation and rolling losses. This calculator adjusts the coefficient using actual and recommended pressure.
Why include road grade?
Grade adds or subtracts tractive force. A climb raises required power. A descent may reduce traction power or create regeneration potential.
Should I include aerodynamic drag?
Use it for high speed, headwind, or route energy estimates. For slow industrial carts, rolling resistance may be the larger concern.
What does battery current mean?
Battery current is the estimated power demand divided by bus voltage. It helps check controller, cable, fuse, and battery discharge limits.
Can this replace road testing?
No. It is an engineering estimate. Use real vehicle testing to confirm tire behavior, drivetrain losses, wind effects, and route conditions.