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TOOLS · CALCULATOR
CPAP battery calculator: how long will your battery last?
This CPAP battery calculator estimates how many hours a battery will run your machine at your pressure and humidifier setting, then plans how many batteries a trip needs and whether they can fly in the cabin. Treat the result as a planning estimate and test before you rely on it.
- About 1 minute
- Free, no sign-up
Free CPAP battery calculator. Estimate how many hours a battery runs your CPAP at your pressure and humidifier setting, plan a trip and check FAA carry-on limits.
What your result looks like
A sample result. Yours appears here the moment you finish, with what it means and what to do next. Every possible result is listed beside it.
Part of a night
6/7.5
07.5
This battery covers part of a night.
Turning the humidifier and heated tube off usually adds the most hours. A second battery or a larger one closes the gap.
- Usage hours and adherence
- Travelling with CPAP and your data
7.5–+Covers a full night
This battery should cover a full night at your settings.
Either side of 10000Part of a night
This battery covers part of a night.
Either side of 10000Too short
This battery will run out well before morning.
Use the calculator
Pick your machine, pressure, humidifier setting and battery. Add trip details for a full plan.
What this tool does
The battery calculator is for camping, power cuts, long flights and anywhere without a wall socket. It estimates runtime from published-style draw figures and your settings, and checks your batteries against US air travel rules.
It cannot measure your actual draw. Breathing pattern, leak, altitude and cold all change it. Run the battery for a full night at home before you depend on it, and check your machine maker's battery guide.
How the calculator works
Runtime in hours equals battery watt-hours times the usable fraction, divided by the machine's draw in watts.
Usable fraction. Not every watt-hour reaches the machine. On a DC connection, plan on about 85 percent. Through an AC inverter, conversion losses cut that to roughly 60 to 70 percent; we use 65. Batteries over two years old lose capacity, so we take off a further 20 percent.
Draw. Base draw at 10 cmH2O with the humidifier and heated tube off:
| Machine | Base draw (W) |
|---|---|
| ResMed AirSense 11 | ~10 |
| ResMed AirSense 10 | ~11 |
| ResMed AirCurve 10 / 11 | ~13 |
| ResMed AirMini | ~5–6 |
| Philips DreamStation 2 | ~10 |
| React Health Luna G3 | ~12 |
| Transcend Micro | ~6 |
Pressure factors: 6 cmH2O ×0.75, 8 ×0.85, 10 ×1.0, 12 ×1.15, 14 ×1.3, 16 ×1.45, 20 ×1.8. Humidifier add-ons: low +15 W, high +35 W, heated tube only +20 W, both +50 W.
Worked example. AirSense 10 at 10 cmH2O, humidifier off, 95 Wh battery on DC: 95 × 0.85 = 80.75 Wh usable. 80.75 ÷ 11 W = about 7.3 hours, just under one 7.5-hour night.
Reading your result
Covers a full night. Seven and a half hours or more. Still test at home first.
Part of a night. Four to under 7.5 hours. Switch humidification off or add a second battery.
Too short. Under four hours. Consider a larger battery, a DC connection or a travel machine.
Flying with CPAP batteries
US FAA rules for spare lithium-ion batteries in passenger baggage:
| Battery size | Cabin | Checked bag |
|---|---|---|
| Up to 100 Wh | Allowed | Not allowed as a spare |
| Over 100 to 160 Wh | Airline approval needed; two spares maximum | Not allowed as a spare |
| Over 160 Wh | Not allowed | Not allowed |
Spare batteries go in your carry-on with terminals protected. Airlines and other countries can be stricter, so check with your airline before you fly. Many airlines also ask you to arrange in-flight CPAP use in advance.
Your Apnealytics data helps here too. Your real pressure P95 gives a better estimate than your prescribed maximum, and the dashboard shows whether nights away kept up your usage.
Sources
- US Federal Aviation Administration. PackSafe: lithium batteries. faa.gov.
- US Code of Federal Regulations, 49 CFR 175.10, exceptions for passengers.
- ResMed, Philips, React Health and Transcend battery and power guides.
FAQ
How long will a 95 Wh battery run my CPAP?
At about 10 cmH2O with the humidifier off, a typical home machine drawing around 11 watts runs roughly seven hours on a 95 Wh battery over DC. Turn the humidifier on and that can fall to a few hours. Your own pressure and breathing change the figure, so test a full night at home.
Why does the humidifier drain the battery so fast?
Heating water and a heated tube takes far more power than moving air. On many machines the humidifier can use more energy than the blower. Switching it off, or using a waterless travel option, is usually the single biggest way to add hours on battery power.
Can I take a CPAP battery on a plane?
In the US, lithium-ion batteries up to 100 Wh can go in your carry-on. From 100 to 160 Wh you need airline approval and may carry two spares at most. Over 160 Wh is not allowed. Spares must not go in checked bags. Always confirm with your airline before travel.
Should I use DC or an inverter?
DC whenever you can. An inverter converts battery DC to household AC and the machine's power supply converts it back, losing energy both times. A DC cable or converter made for your machine typically gives noticeably more runtime from the same battery.
How does Apnealytics improve the estimate?
If you are signed in, the calculator can use your pressure P95 from the last 30 nights instead of a guess. That is the pressure your machine actually reached for most of the night, which is a better input than your set maximum. Your result is saved for the next trip.
Diagnosed and on CPAP? See if it's working.
Apnealytics reads your machine's SD card and shows residual AHI, leak and usage every night. Your first 30 nights are free.
