95% of our camping is boonedocking and I use a cpap. Here is my progression over the last 5 years.
I bought the Harbor Freight 5 in 1 power pack. First weekend I used it's inverter and the machine's 110 plug. It would not last more than 6 hours without a recharge.
The next trip, I had bought a 12v power cord for the cpap and used the 12v outlet on the power pack. Much better without the inverter on, and it would go for a couple of nights.
I won a Optima Red Top battery at a Jeep Jamboree raffle. Completely sealed maintenance free battery. Made to fit in a Jeep, so not as huge as some car batteries. I had just bought a new battery for the Jeep. So, I picked up a 12v outlet with alligator clips to attach to the Optima, and it's been my cpap power source. I have yet to run out of power for my cpap even after a week out. Simply hook the battery to the charger/maintainer when home and it's good to go for the next trip. Having a extra battery around can come in handy also in a pinch.
