Battery size for camping with CPAP using heated humidifier

Hi, I've been doing a ton of research on what size battery or power bank I would need to power my dreamstation 2 for a full night using the heated humidifier. I have gotten so much info it's making my head spin. I know that my machine pulls 12volts at 6.67amp at the power source. And that if I could power my machine by DC power instead of going from AC to DC it would be much more efficient. I looked up the manufacturer's battery but they only power the cpap machine for the most part, and I'm looking for something that can run the cpap as well as a fan etc. So many of the power banks/batteries on Amazon state that they can power anything but the reviews say differently especially when using the humidifier which really helps. And I don't want to spend thousands of dollars on a device that I may only use twice a year. Any help is appreciated.

Here is the ResMed Battery guide.

https://document.resmed.com/documents/a ... lo_eng.pdf

I know you don't have a ResMed, but if you know what your draw is, you can find an equivalent draw, and look up what size battery (measured in AH) would suffice.

That is until you say, "as well as a fan etc".

buy 100 amp battery

The Resmed battery guide posted above is a great resource to give you an idea of CPAP power draw with and without a humidifier. It nicely illustrates how power draw varies per therapy pressure and the humidification setting. Ballpark per this guide the typical machine and therapy settings will draw .5 to .75 amps per hour for the machine alone and with humidification this jumps to roughly 3 -5 amps per hour. Note that extreme settings (e.g. max pressure and max humidification can go outside this range). The 6.67 amps noted in the OPs message is likely the max power rating of the device/power brick, not the actual power drawn as that will vary per your therapy and humidification setting.

Using 5 amps per hour, as a likely power requirement for 8 hours of sleep, requires 5x8 or 40 amp hours of power with humidification. Two nights of use will require 80 amp hours. For 80 amp hours of power the post above recommending a 100 amp hour batter will work though this is the minimum capacity required if you decide to use a lead-acid AGM battery. AGM batteries should not be cycled (drawn down) by more than 80% of capacity. For camping it's ideal to have some reserve so a 125 amp hour battery may make more sense. For just one night a 50 amp hour or more ideally a 75 amp hour AGM battery, to ensure adequate reserve, should work. For safety make sure you install these in a battery box with safe connectors, wiring and fusing that minimize the chance of a short circuit. I've seen videos of folks just placing clamps on the exposed connectors of these batteries while camping which is not safe. If you drop a metallic object on the exposed battery terminals the short circuit of 100's of amps over a few seconds will weld the object to the battery and create a fire hazard.

These are heavy batteries with 100 ah and 125 ah batteries weighing roughly 65 and 75 pounds respectively - you are not going to back pack with these and may need two people to move them. Costs run from $175 to $250+ for these batteries. Additionally you will need connectors, wiring, fusing, etc and a battery box. See the thread from Capn Loki that has lots of instructions, including my own, on how to do this. Note if your CPAP does not run directly on 12 volts you will need a converter and extra capacity given conversion inefficiency.

For comparison purposes 100ah Lithium Ion battery now seem to be selling for around $300 on Amazon and only weigh around 25 pounds. This battery chemistry can be drawn down to almost 100% of capacity so for two nights 100ah should be plenty of capacity. You will need to research how to charge, wire and fuse one of these safely as I've only built my camping power packs with lead-acid AGM batteries.

If you can live without the humidifier battery requirements fall dramatically. My power packs (have 2) are build around much smaller 20 amp hour AGM batteries that easily support my CPAP at 10 cm of pressure (only draws 0.6 amps per hour) for two nights with plenty of reserve left over for running a small fan at night (.45 amps per hour) and charging cell phones etc. The batteries only weigh about 13-14 lbs. With two of these and a 30 watt solar panel we camped for a full week during the summer on a beach camping site a few years ago. Note that for camping during a less sunny time of year or location one would need to at least double the solar panel capacity.