Good thread, fun stuff. Here are a few non-technical contributions:
Resmed versus others: I want to gripe about the Resmed-bashing that has been inspired by the connector conspiracy. ("I'd like to complain about people who hold things up by complaining about people complaining.") There are far more important things here than which manufacturers let you use a 12V battery without a converter. Shouldn't we decide which machine we want to use based on the
internal features and performance in objective comparisons of the various makes & models, rather than whether we have to buy another cable (or maybe build one)? Deciding based on the cable is absurd. Elsewhere, I mentioned all the good points I could think of about the De Vilbiss DV54, then I said "But none of these has anything to do with CPAP! What is wrong with this picture?" Judged as a CPAP/APAP machine rather than a UPS, the DV54 turns out to be mediocre.
In my experience, Resmed does many things right except for (speaking of Resmed-bashing) the vile P10 mask (I fart in its general direction) and the lack of an on/off switch for the cellular modem. The Air10 machine itself, either Airsense or Aircurve depending on your needs, is ab fab. So anyone who is shopping around and deciding what to buy shouldn't pay any attention to complaints about the special cable. Buying that converter is a little bite, not a big one. Or if you want to make a converter, that's great. If you already have an A10 or an S9, there's no reason to get a different machine unless you need to minimize weight for backpacking. As for dropping Resmed and buying some other brand just because of the connector conspiracy, as someone mentioned way back in the thread, that's even more absurd. Anyone who is willing to give up all the benefits of the excellent Resmed firmware for that trivial reason needs a check-up from the neck up.
Off-the-shelf DC-DC converters for Resmed: For anyone who doesn't want to do the home-brewed stuff, the Battery
Power Solutions DC-DC converter, which I think has BPS part number FBA_BPSC-24V-RES (at least that's what it's called on Amazon), around US$70, is more versatile than the Resmed 37297, which is specific to the A10: the BPS has more options for cables & connectors, not just a cigar-lighter plug on one end and the Resmed DC plug on the other. In addition to the A10 & S9, it can be used to
power other devices, not only CPAP machines, that take 24VDC without the Resmed Masonic handshake. As was mentioned upthread, the Resmed converter can use either 12V or 24V as input, and the same is true of the BPS, in case you have a 24V
power source and you want to add the Resmed handshake to that.
Off-the-shelf DC-DC converters for others: For any device that needs 24V without the Resmed thang, a slightly less expensive 12-to-24 converter is the Bix
power DD90M-24V, US$50, which the manufacturer claims is very efficient, 96%. One reason I mention it is that the Philips Dreamstation Go wants 24V but its proprietary battery costs about US$300, ouch!, for a puny 62 watt-hours (one night's worth).
Li-ion batteries: There have been more lithium-ion battery products, at least (I don't know about SLA/AGM, etc.), introduced in the last few years, so it's a good idea to do a lot of window-shopping before buying anything expensive. A while ago I started a thread in the Other Product Reviews forum about
a Gissaral 130-Wh Li-ion battery, and that includes some more general information, although it's about backpacking rather than UPS setups at home where the weight doesn't matter. I don't recommend the Gissaral for reasons mentioned there, but some similar products look very good, including one from Renogy (266 Wh) and one from XT
Power (195 Wh). These days, you should be able to get three nights of unheated CPAP use from a high-capacity Li-ion battery before recharging, if you don't mind that the battery weighs about 3 pounds.
So there's no need to settle for the lame Li-ion batteries that are sold specifically for CPAP: the ones branded Resmed, Philips, BPS, Medistrom, Bix
power, and
Powermod. Each of those has a capacity under 100 Wh, is good for only one night of CPAP, and costs between two and eight times one of the alternatives I've mentioned. However, if you have money to burn and you'll be using the thing as part of a UPS setup at home where the max duration of the "
power outrage" (sic) will be 8 hours, those CPAP-intended products should work fine (with the machine's heaters switched off).
With a full-size machine and an arbitrary third-party battery, be sure to plan for the startup current, probably 3.75A or thereabouts.