It sounds simple, but it is not a real easy thing to do. First I would suggest reading this ResMed Battery Guide document. It gives you an idea of what size a battery you need in amp hours. However there are many complications. First is that ResMed runs their equipment on 24 volts instead of 12 volts. For that reason you need to use your standard power supply and plug that into an inverter, which is in turn powered by a battery. That is the least efficient method, but potentially the most reliable. We use a 5th wheel travel trailer and both myself and my wife use a CPAP. When we are plugged in to AC there is no problem. But when off the grid we need to run off the 12 volt DC. An inverter works but if you push it too hard the cooling fan will come on during the night and make a lot of noise. Assuming it is for short term use the best thing you can do is change the settings on your machine so it does not use the humidifier and does not use the heated hose. This greatly reduces the current draw. When off the grid I have a 70 watt solar panel that I use to recharge the 12 volt batteries in the trailer. To recover from each night, I bought the DC to DC converters that ResMed sells and are described in that document, and are claimed to be more efficient. The one for my AirSense 10 seems to work well. However, the one for my wife's S9 does not. Unless she turns off the heated hose and humidifier it trips out repeatedly during the night. I am on converter #3 from ResMed and the problem still exists.
The next issue is the battery to take on a plane. You can look up in the tables in that document what size a battery you need, but it is significant. A motorcycle battery might work, but it is not really designed for deep cycle, and I really doubt they would let you take it on a plane. They are probably going to be looking for something that is from ResMed and considered to be medical equipment, and even then if it is Lithium Ion, alarm bells are going to go off. In short I am not sure how you could get something to use on the plane. Your machine is a specialized unit and an ordinary CPAP is not going to work. There are very portable version of a CPAP that have an included battery, like the Z1 auto or possibly now the Z2 auto. Those you are likely to get on a plane and survive for the length of a flight. But they are basic APAP machines, not ASV machines.
So in summary, off the grid, but not on a plane, a deep cycle 12 volt battery will work, with a 12 volt DC to 24 volt DC converter, or with an inverter. A 70 to 100 watt solar panel should recharge it on most days if you shut off the humidifier and heated hose. A larger battery than the minimum size recommended in that document will give you more reserve.
Hope that helps some,
Wow! My electrical competence is limited to plugging in a plug, turning the TV on and off and changing a light bulb. The Resmed battery guide is incomprehensible to me. I was hoping for a simple solution but there doesn't seem to be one. Thanks for your comments Sierra.
Let me try to help a bit. First off, I am not sure how one could get a battery arrangement for a full sized home machine on an airplane. Not optimistic there is a solution, with regulations today, but their might be. I believe some planes do have 110 volt ac on them and if you had that, then you could just plug in your normal power supply. There may be a current limit, but if you turned the humidifier off and heated hose off, you could be within that limit.
In a home or camping battery situation, the most straightforward way would be to get a 12 volt deep cycle battery at Canadian tire. They have their own standard lead acid brand, or you could go for an AGM type for more reliability and less chance of spilling acid at an extra (2-3 times more...) cost. If you use a 12 volt to 24 volt converter from ResMed that is the most energy efficient way to get the needed 24 volts. They are about $130, but you should check with ResMed or the dealer that they will fit your ASV machine. The other way is to just use a 300 watt inverter available at Canadian Tire. They are cheaper but not as efficient. As far as battery size have a look at this table.
The top situation is without a heated hose and the humidifier turned off. At a 16 cm IPAP it suggests that current draw (at 12 volts) would be 1.23 amps and a 15 amp hour battery is recommended. That is a fairly small battery and a lawn tractor or motorcycle battery might work. However they are not deep cycle and can be expensive. A full sized 24 or 27 deep cycle battery may be more practical, but much heavier. If you take the more normal second last case in this table with the heated hose and humidifier on in Auto, and a 16 cm IPAP, it says 4.21 amps and a 51 amp hour battery. That is pretty close to a normal size 24 battery like this one at Canadian Tire, which is rated at 65 amp hours.
Based on our camping experience, I would suggest a 100 watt solar panel is about the size needed to recover each day from the night before.
Hopefully that helps some.
Thank you Sierra. The information is very helpful. I was originally thinking of a Freedom lithium battery which I could take on a plane but I do not think its strong enough.I will just buy a deep cycle battery when I am in Mexico. I assume that my ASV will use a little more power.It is not listed above.