(05-08-2013 08:06 PM)TinyL Wrote: Went and purchased a lithium battery for when I am camping with the ResMed DC Converter and that sets me up as far as camping. But now I am looking for home battery usage. I was just going to go get a big deep cycle battery and keep it handy...but then I was wondering if one of these uninteruptable power supplys would be enough to get 8-9 hours of full service with the humidifier on. Was thinking this would be good bang for the buck since you get surge protection, battery back-up and don't have to wake up to change over. But I am not really sharp at figuring out this whole amp hours and what / how big a unit I would need to operate a S9 AutoSet running 9 H20 with humidifier on. I know APC and other companys make lots of different sizes but I don't know what would work. I can find lots of threads on camping batterys but nothing talking about the UPS units. Do they have enough oumph?
Like you, I have a lithium pack for outdoor activities and air travel.
As far as home backup solutions go, I use an off-the shelf Cyberpower Systems pure sine wave UPS rated at 1000VA.
This UPS puts out a pure sine wave (I use a Resmed machine), is small, ultra quiet, relatively cheap, and has a muteable low battery alarm. You also get 350k$ of surge damage insurance for connected equipment (just a nice-to-have). The 1000VA model is available at Amazon for 110$US. Amazon also sells the 1500VA model for 180$US.
Since the 1000VA UPS has a 9Ah battery, it can run my S8 Autoset II + H4i humidifier for a full 30 minutes. However, I only need a few minutes when an outage happens since I then switch over to my lithium pack.
I use the UPS mainly for protection against surges and power fluctuations but also as a nighttime "alarm" to wake me up when a power outage actually occurs while I am sleeping. I then manually switch over to my small Li-Ion power pack (3 lbs., about the size of a book) which can last me 3-4 nights (sans humidifier). This is not quite as convenient as just sleeping through the outage but I have to get up anyway to switch off power bars on computer and home entertainment systems to avoid damage from the fluctuations on the power lines as the utility restores power. Since I already have the Li-Ion pack for fishing/camping/trekking/travelling, this approach allows me to avoid building a custom CPAP UPS and dealing with the bulk and maintenance of a deep cycle battery.
Power outages here only happen a few times a year and last from 1 to 3 days. If the frequency of power outages in your area is higher and if you are less concerned about damage to your computers and home entertainment systems than I am, the custom deep cycle battery approach makes sense.