D · Interactive tool · Module 03
Power Budget & Battery Runtime Estimator
Sum the loads, apply converter losses, size the battery and the converter, and check the voltage drop in a cable run.
Preliminary engineering guidance. Results depend on the assumptions listed below and on simplified models. Verify with manufacturer datasheets and a test on your own hardware before committing to a design.
Loads
| Load | Average (W) | Peak (W) | Duty (0–1) | Via DC-DC | Remove |
|---|
Battery and converter
Depth of discharge you will allow.
From the battery datasheet; 0 to skip.
Result
Cable voltage drop (copper, round trip)
Assumptions and limitations
- Runtime = nominal energy (V × Ah) × usable fraction × (1 − aging derate) ÷ average battery power. Loads behind the converter draw power ÷ efficiency.
- Not modelled: Peukert effect, temperature, voltage sag under load, converter efficiency varying with load, motor regeneration. Treat the runtime as an upper-bound planning figure and measure it with a discharge test.
- Average power depends on the duty cycle you enter; the figure is only as good as your duty-cycle estimate. Measure real current with a logging shunt on the prototype.
- Converter rating = peak output power of the loads it feeds × margin. Check the datasheet for the input voltage range, peak versus continuous current and thermal derating.
- Cable drop uses copper at 20 °C (1.68×10⁻⁸ Ω·m) for supply plus return conductors. Resistance rises with temperature and with every connector; the figure excludes connector resistance.
- Default values are placeholders to show the layout, not recommendations.
References
- Copper resistivity at 20 °C: 1.68×10⁻⁸ Ω·m (standard reference value).