What is the Peukert/efficiency factor?

Real batteries deliver less energy than their rated capacity due to heat, internal resistance, and discharge-rate losses. A factor of 1.0 means 100% of rated capacity is available; 0.85 is typical for LiPo/Li-Ion packs; 0.7–0.8 for older NiMH packs. Lower values give more conservative (safer) estimates.

Which input should I use — mAh or Wh?

Use mAh when you know the battery nominal voltage (common for single-cell or standard packs). Use Wh when the manufacturer provides energy directly (common for larger multi-cell packs). The calculator accepts both; if you enter mAh it multiplies by voltage internally.

Why does my calculated runtime differ from the manufacturer spec?

Manufacturer specs are usually measured at a very low, constant discharge rate. Real robots draw variable, often high, currents — motors during acceleration peak significantly above idle. Use the efficiency factor to model this gap.

Can I use this for drones?

Yes. Enter total pack capacity (mAh × voltage = Wh), set the average draw in watts (hover power is a common estimate), and apply an efficiency of 0.80–0.90. Drone packs discharge faster so a lower factor gives safer estimates.

Robot Battery Runtime Calculator

Estimate how long a robot battery will last given capacity, voltage, current draw, and efficiency.

Battery & Load Parameters

Capacity Input Type

Battery Capacity (mAh)

Nominal Voltage (V)

Load Input Type

Average Load (W)

Efficiency Factor (0.01 – 1.00)

0.85 = 85% usable. LiPo: 0.80–0.90. NiMH: 0.70–0.80.

Enter battery and load values, then click Calculate Runtime.

Quick Examples

Summary

Calculate robot battery runtime from capacity (mAh or Wh), operating voltage, average current draw (W or A), and an efficiency/Peukert derating factor. Results show estimated runtime in hours and minutes, usable energy, and consumed power.

How it works

Enter battery capacity in mAh or Wh and operating voltage.
Enter average current draw in watts or amps.
Set a Peukert/efficiency factor (0–1) to account for real-world losses; 0.85 is a common default.
The calculator converts mAh to Wh when needed, applies the efficiency factor, then divides usable energy by power draw.
Runtime (hours) = (Capacity_Wh × Efficiency) ÷ Load_W.

Use cases

Estimating field-mission duration for an autonomous ground robot.
Sizing replacement batteries for hobby drones and RC vehicles.
Comparing battery packs with different voltages and capacities.
Validating power budgets during robot design before hardware is ordered.

Frequently Asked Questions

Last updated: 2026-06-18 · Reviewed by Nham Vu