Harlan,
If your machine is like mine, it really doesn't draw all that much.
Mine uses less than 2 amps while I'm using it. This is less than many
of my cabin lights and a lot less than the computer I'm typing on.

I have 3 group 27 batteries of no particular brand (2 are LTH, a Mexican
brand and one I got at Costco). We are conservative with our electrical
use, especially in cloudy weather since all our power comes from solar
panels and can go 4 - 5 consecutive cloudy days before having to start
the engine to charge them. We also have a dedicated starting battery so
if we do draw the house bank down too far, we can always start the
engine. I would strongly recommend that you install a Link 10 battery
monitor like we have (or some equivalent) as it takes all of the mystery
out of managing your power.

Whatever you do, don't elect to go without the CPAP machine. As you are
no doubt aware, for those of us with sleep apnea, life sucks without it
and night watches are virtually impossible.

Have fun - Dan

Harlan Lachman wrote:

I have sleep apnea. That means I have to hook up my nose to a machine
blowing air into me all night long. Heated humidification makes it
better but in the summer, if humidity levels are high enough is not as
important.

This takes electricity. At a dock and plugged in, no problem. But since
I have been plugged in, I have not had the joy of dropping a hook in a
beautiful gunkhole. This is gonna change.

Anyone have a recommendation for a deep cycle battery with lots of (the
most?) amp hours which I can drain at night and rely on fully recharging
during the day?

harlan