Best CPAP backup battery?

I love the portable outlet battery. I use it with my resmed AS 11. I camp off grid. the power pack will use only 50 percent of battery capacity with air only 8 hours. it takes about 3 hours to recharge the battery back to 100 percent. you have two ways to recharge it. use the plug that comes with it. plug to ac. when off grid. I use the portable inverter you can buy to recharge it from a deep cycle battery. the batteries they put in it are excellent quality lithium. this power pack will last if you use it wisely. never run down battery capacity below 20 percent. try to keep it around 50 percent. I paid 300 for mine. if you shop around. I know you can get the same price too. this is a very good product. only bad thing I can say about it. its expensive. you get what you pay for when you buy lithium. not all lithium batteries are the same quality. there are a lot of junk lithium batteries out there too. yes the batteries are made in china. if you want American made. put people back in office that put the United States first, if you want American made.

It's fairly easy to build a 12 volt battery pack with a 35 Ah AGM battery, which combined with a simple adapter, will power a resmed (no humidifier) for somewhere in the range of 3-6 nights. Not very portable, but not expensive, and best of all, will take you through more than a night or two without power. Search is your friend.