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Target-duration planning

Run a CPAP for 2 nights from a power station

This pilot uses an explicit 8-hour-per-night planning target and the no-heated-humidifier CPAP scenario. Change the hours and watts if your prescribed setup differs.

Target

2 nights (16 hours)

Planning load

40 W

  • Running watts: 40 W
  • Duty cycle (%): 100%

Estimated nominal battery

850 Wh+

Scenario confidence

estimated

Verify your watts

  • Check the device label for running watts or input amps and volts.
  • Use a plug-in watt meter for AC loads when the result matters.
  • For cycling loads, measure long enough to capture on/off behavior.

Open wattage library

Check output path

  • AC inverter loads usually lose more energy than direct DC loads.
  • Keep reserve for cold weather, battery age, and load changes.
  • Do not treat label capacity as fully usable watt-hours.

Read the method

Medical-device planning

  • Use this site as a planning estimate, not medical advice.
  • Follow the device manufacturer's battery guidance.
  • Test the full setup before relying on it overnight.

Reverse runtime formula

This page solves for battery Wh instead of asking how long a battery lasts.

Load energy

40 W × 2 nights (16 hours) = 640 Wh

Usable factor

85% × 90% × 100% × 100% = 0.77

Estimated nominal battery

640 Wh ÷ 0.77 ≈ 850 Wh

Scenario behavior

The CPAP no-humidifier scenario is treated as a continuous load. Heated humidifiers, heated tubes, pressure, mask leaks, and AC vs DC power paths can change draw materially.

Wh-class guidance

Use the computed Wh as a no-humidifier planning floor. Add a larger margin or switch to the heated-humidifier scenario when comfort accessories are enabled.

Assumptions used

  • CPAP without heated humidifier: 30-60 W
  • Efficiency (%): 85%
  • Reserve kept unused (%): 10%
  • Output path: AC inverter
  • Battery health (%): 100%
  • Cold weather loss (%): 0%

Caveats

  • This is a comfort-focused estimate, not medical advice. Use the device manufacturer's battery guidance for critical backup planning.
  • For critical medical backup planning, follow the device manufacturer's battery guidance.
  • Test the exact CPAP setup before relying on it overnight.
  • Keep an independent backup plan for medical-adjacent use.

Sources

Humidifiers and heated tubes can more than double power draw. This is a comfort-focused estimate, not medical advice. Use the CPAP manufacturer's battery guidance for critical planning.

Next steps

This pilot uses an explicit 8-hour-per-night planning target and the no-heated-humidifier CPAP scenario. Change the hours and watts if your prescribed setup differs.