Offgrid is correct. I have the same cPap and that is what I used. I installed a cigarette lighter outlet on the panel under the bed. You may want to upgrade to better batteries though; you don’t want the battery(s) to discharge less than 50%. You’ll also want to shut off the humidifier. It’s a major power hog. 

You may find this useful - https://www.cpapsupplyusa.com/PDFs/resmed%20batteryguide.pdf

Check a site called cpap.com.  Back in 2016 I purchased a "DC Converter 24V 90 Watt for S9 Machines" to power my S9 ResMed CPAP unit.  The converter package included a cigarette lighter plug, the converter brick, and wires to connect the brick to the CPAP machine.  The package also provides wires with alligator clips if you want to go directly from a battery.  The unit cost $84.95 at that time.  Also check www.cpap.com/productpage/dc-conveter-for-s9-machines.html  which provides detailed information with regard to current draw at 12v DC, battery amp-hour requirements for different treatment pressures and a lot of other good information.  The unit has worked very well for me.  The 800 number for cpap.com (at least in 2016) is 800-356-5221.  I would guess they make converters for many ResMed series machines.  Good Luck.

Okay, I did a real quick web search. Your Resmed Airsense 10 runs on 24V. https://www.resmed.com/uk/en/consumer/products/accessories/air-10-dc-dc-converter.html

You would need to get a 12V to 24V converter. You could check Amazon for this item.

I think its not a fuse because it can work on the cpap battery but not on either car. We also have this weird cord that has a 12 volt socket on one end and little clips like jumper cables on the other.  I think that can connect directly to one of the camper batteries but we'd have to slam the door on the cord.  

how fun is all this?

If you don't have any leak problems and all your appliances and fixtures work as they should (check both gas end electric operation before you go in) then I can't think of anything else you might want to have the RV place check for you. 

I'm still messing with strategies for my traveling companion's CPAP. 

We're taking the pod in tomorrow to have bearings repacked, brakes and tires checked and were going to have a DC socket installed because we have a power cord for the CPAP that plugs into the device on one end and a CPAP battery on the other with a DC socket.  (Before you ask the external CPAP battery won't last long enough to be more than a backup option).  The CPAP battery does work but the DC plug won't run the CPAP in either of our cars.

Any thought on why this would be? Is it because this particular CPAP might need an inverter and the battery supplies one?  If it won't work in the car it won't work with a DC outlet installed in the camper either, will it?

While we're at it, is there anything else we should have looked at while we're at the RV shop?  This will be our first visit there and while the 2016 pod is in great shape we don't know what's ever been done (we have been maintaining the batteries).

I'll appreciate your opinions.