I have a Maxoak CPAP battery backup, which is supposed to be good for three nights, but I have not had to use it yet. It was $250 from Amazon when I bought it.

Thanks Lars I will have him look into that one.

CPAP battery descriptions are often stated (in the sales specs) in blah blah evasive ways. Forget how many nights and hours of use are claimed, what size battery you need is something a buyer needs to determine themself. Higher pressure settings draw higher amounts of power. Having the humidifier on (a bad idea when using battery power) will drain any battery quickly.

Refer to the CPAP device manufacturer info (even call them) or other info source to get the power draw in watts or amps. Let that guide the battery selection.

Two other tips:

1- Most CPAP devices run internally on DC -the boxy device on your power cord is a transformer. Most will run on direct DC input. However, some batteries don't have DC sockets to plug into (they look like the old cigarette lighter sockets in cars).

Think of how dumb this is to understand how power gets wasted when there's no DC socket:

To allow an AC connection, the battery needs to have an internal inverter (the opposite of a transformer) to change its native DC into AC. Then, on the power cord, there's a transformer to convert the AC back to DC. The conversion of DC to AC and then back to DC consumes power and will limit the hours of use the battery will produce. Better to get a battery with a DC socket and a proper cord to plug into it and the CPAP machine.

2- My CPAP doc suggested using a form of Power Station device. Sometimes used by campers, sometimes for construction teams, they tend to be priced without a "medical device" premium and also most have DC sockets.

Good luck.

Thanks Elmer. My DH has already gone into the fact that I normally use a hose heat and humidity. I tell him I can turn that off in the middle of the night if the power goes out. Awkard but doable. I have to have high pressure and that I cant change anyway. He just wants as much info as possible. I read him what you wrote and he seems to know what it all means. He is not concerned about cost as much as will it work. Our power can go out a lot.

Yes, I get it. I bought my first battery maybe 20 years ago and have learned the hard way.

Another option I didn't mention that some use - it's a bit bulky, unsightly, and can be slightly unsafe if not used carefully. But guaranteed to work and a tad cheaper....

A "deep cycle" 12 volt marine or RV battery. Deep cycle means it's made to sustain a low power discharge over a long period of time. Many batteries can't. It looks like a car battery but smaller.

To use one, you need a V-shaped device with an attachment for each battery terminal on the two ends, that to join to form a 12 volt socket at the base where the two legs meet. The same kind of socket for 12 volts I described above. Plug in your 12 volt plug with the suitable CPAP male plug on the other end and then sweet dreams.

Such batteries are recharged using a charger intended for a car battery.

Thanks Elmer. You two are thinking a like. Like you he understands this stuff. I do not do electricity. I just lean toward more tidy than trickle chargers on ugly batteries with wires everywhere. He just wants the best possible system and of course we have to be sure it is compatible with my oh so expensive machine. For me it is an issue of UIP vs just a big battery that I would switch to with the hose heat and humidity turned off I think.

I hope I helped. Believe me, I mostly don't understand electricity either. I tried some years ago to understand it in many respects, including how the semiconductor devices my clients made or used in their products work and ditto for other solid-state devices. I just can get with the flow. ;-)

My knowledge is the hard knocks kind, having previously bought wrong batteries because of relying on the marketing information. They led me astray but also led me to dig in more to understand what works and why and what doesn't and why.

I need to replace what I have (an old ResMed lead acid battery that will no longer hold a charge) and I'm leaning toward a power station type device. My sleep doc takes hers camping regularly and she said her pressure settings are about the same as mine. I also had lithium ion batteries a few iterations ago and they worked fine but didn't last long. And, at that time, the price to capacity ratio was high and what I needed (again at the time) cost over $500. They're cheaper now.

For more info, you can go to a Sleep Apnea Forum and ask questions there. That is where I got information before I bought my battery. I don't have my login info for this forum with me at the moment, but when I go back to my regular computer, I will be able to find it.

My issue now is that I bought my battery for my ResMed 9, and today I have a ResMed 11, and I'm not sure that the battery is compatible - mainly because of the power cord from the battery to the machine. I'll have to check it.

I still have my old machine, and so I could always use that, if necessary. I'm still in the process of moving, and so I still have half of my stuff at each house.

Lars, electricity is electricity. Check the plug in to the device, I'll bet it's the same. You could also compare the plugs on the wall cords too.

Fortunately I have a stand-by generator for my house. It's really gives me peace of mind (I have an all-electric house).

I have a small generator that I use for our fairly frequent winter outages. I bought a battery pack and the adapters necessary to fit my cpap. I was not good about keeping the battery charged per their recommendation to charge it monthly, I believe, and when I went to make sure it was charged for a coming winter storm, it would not charge more than 60% and did not hold the charge. For the few times I actually used it before then, I just recharged the battery pack daily with my generator. It also had an adapter to charge in your car, if needed. I also ran it directly off of the generator a time or two, which allowed me to use the humidifier and heated hose.

Usually the power goes off in the winter and the heat from my woodstove doesn’t reach my bedroom, so cold air being blown into my nose isn’t pleasant. I have a different cpap now so will be shopping for a new battery pack, too. I will be interested in what you select, Patricia. I bought one for my Starlink set up that keeps the system from going offline every time there is a blib in electric service, which requires rebooting and reconfiguring everything. I can use that one for my cpap in a pinch.