Very good advice on Solar as stated above. :)
Quote from RoyB "your CPAP draining 12VDC@3AMPS needing to run for 8 hours will consume 24AHs of capacity"
Thing is, you have TWO to run. The draw is also determined by whether you use one or both with or without a humidifier.
How often do you Dry Camp ? For how long of time ? What converter/charger do you have ?
Myself, I cannot go without my CPAP. I use a dedicated sealed battery for it & charge as needed with my portable battery charger & generator. My converter/charger is old & worthless for charging purposes.