Only the ResMed is 24 volt...the rest of them are 12 volt or something in that neighborhood.
The ResMed can be easily converted though...just need a little converter.https://www.resmed.com/uk/en/consumer/p ... erter.htmlhttps://www.resmed.com/uk/en/consumer/p ... erter.html
This would be used with batteries that are 12 volt
Are you wanting a battery back up for other small devices or a full grown generator?
Did you say "generator" but mean "battery"?
Big difference in what they put out. I have a portable generator that is gas powered and big enough to power the basics in my house plus the cpap machine and I have it wired into the house so all I do is plug into the same electric outlet. It sits outside the house though.
A battery would be inside the house and size of the battery would depend on how you want to use it...and for how long and how are you going to recharge it.
Were you maybe looking at the portable batteries targeted for powering cpap and small devices like phones, etc?