I just picked up a new 24V CPAP machine (ResMed AirSense 10). This replaced a 20 yr old machine that I ran off AC at home and 12V DC in the RV (used the 12v TV outlet in the bedroom). Two questions:...
The specific device shown in this link is not likely what you need (not enough current handling capability, or if you like "Not big enough") but it is a CLASS of device that you may wish to consider.