So you are thinkng that the Duracell portable battery pack is better than improving your lead acid battery bank?
I am guessing, but you might be looking at a portable battery pack, perhaps 10 amp hours or maybe 15 amp hours. If it is over 30 pounds, then perhaps might be 20 amp hours, but my guess it is smaller, and will not really power the CPAP machine overnight.
I put 4 each 220 amp hour 6 volt batteries and a 400 watt solar system in one fifth wheel, with a 1,500 watt inverter. The batteries still needed to be recharged after a couple of days from a generator to keep the CPAP running all night long. But he was good for a really long weekend while it was sunny.
So what is it that you want to do?
Do you want to dry camp for 2 nights without running a generator? I can tell you what size battery bank you will need.
3 nights? Just add another pair of batteries.
More than three nights? You will either need solar panels or a generator to keep camping for a while. I was able to camp for weeks at a time with a 400 watt solar system and 4 golf cart batteries. But I did not have a CPAP at the time. If I want to run a CPAP, I will need to expand the solar system to about 600 watts, but can keep the battery bank at 440 AH. I might still need to run the generator a bit, but not as much as soneone without a solar system.
Fred.
