Am adding to this thread instead of any other battery thread because, I guess, it has Oldguide's table summarizing some other battery research, and just because there are too many relevant threads to choose from. This is not about canoe camping, but it is about the opposite end of the product range from, for instance, a large lead-acid battery being used in an RV.
I found a fairly good (for my purposes) cheapie Li-ion battery to provide 12VDC for only one night at a time, at up to 5A peak (startup): the
Gissaral GIS09B-AP3, 130 watt-hours, weight 1.4 pounds, about $80 at Amazon (search for "Gissaral 35000mAh power bank external battery portable charger"). That watt-hour figure is assuming that the stated capacity of 35 amp-hours is at 3.7V, which seems to be the practice of the various manufacturers when publishing those numbers. Using its 12V output, the thing should give a solid 8 or 9 hours of CPAP use at an assumed sustained draw of 1A (no heater, of course!) without completely draining it, and in my initial testing at home, it does that. The stated charging time is 4 hours maximum using the included AC brick (fairly light, about half a pound) with its 15VDC output, or 15 hours through a 5V micro-USB power-in port (fuggedaboudit). The battery has outputs of 5V via several USB jacks and 12V or 15V via the usual 5.5x2.5mm jack, so you can also use it with your phone, tablet, laptop, etc.
The fast-charging input is labeled "15V-20V", and I assume that for motor-vehicle travelers (I'm not one) it must be a serious flaw not to be able to use 12V to charge it, so presumably that would rule out this product for those folks? If so, then use this post only as a general outline of what's possible, and look for a similar but better product that can be charged from 12V. Or else, I guess, do use this product but plan to use an inverter to charge it, further increasing your friendly local entropy. Or make a custom DC-to-DC converter. Whatever works.
Anyroad, the Gissaral unit, and many similar ones from various mfrs, can be paired with the
Battery Power Solutions 24V Power Converter for Air 10/S9 Series and Freedom or C-100 CPAP Battery (Az search), which is around $70 at Az, maybe slightly more at some of Suppliers #1 through #n. That's one of several available converter devices providing the Resmed secret Masonic handshake on pin 3, and I think (someone correct me if I'm wrong) that it's the only one other than Resmed's that is sold as a separate component.
Gissaral and BPS devices, large images behind thumbnails, courtesy of the mfrs:
I'm glad that BPS does sell that Resmed converter separately, but I'm also bugged that its price is ridiculously high. I'd still rather pay $80 + $70 = $150 than a total of $330 for the BPS Freedom kit with a 97 Wh battery, even though that one has a nice digital display ... or $340 for the Medistrom Pilot-24 (also 97 Wh), or $265 for the Bixpower CP170-S10 (higher capacity ... 159 Wh?), or $250 for the Powermod "Knyte Power". All of those products include a Resmed-compatible 24V converter, but I'm enough of a cheapskate and just barely enough of an electronics tinkerer to balk at those prices and to plug together an equivalent kit from off-the-shelf components. And if you think those four are overpriced, try $700 for the Resmed Power Station II. The operative principle seems to be "Never give a sucker an even break, and never smarten up a chump." (I do know how that goes from a chump's point of view; over the years I have paid unreasonably high prices for a few items of consumer electronics, as I'm sure most of us have at one time or another. I just didn't want to add another item to that list, thus my recent consumerdroid research ending, at least for now, in the selection of the Gissaral gizmo.)
What gets me about the price gouging is that a DC-only power supply doesn't have a Medicare HCPCS number and isn't considered essential equipment by the insurers, so you pay for it yourself. That point is even in BPS's own FAQ. (Of course, BPS is doing great by cutting Resmed's retail price in half; end of story, right?)
I haven't bought the Resmed-compatible converter yet, so initially I'm testing my Gissaral at home with a De Vilbiss DV54, which is in the IntelliPAP 1 series (not IntelliPAP 2, whose power requirements are different). In the case of the DV5x machines, a straight-through power cable from the battery's 5.5x2.5mm jack to the DV's 5.5x2.1mm jack, 12VDC with the usual tip positive, is all that's needed. The DV5x automatically disables its heater (assuming that the humidifier base unit is attached to begin with) when using DC power. Depending on how you're providing the DC power and whether you want heat, that could be good or bad. With a small Li-ion battery, it's good, or at least necessary, and you can still use passive humidification.
The battery will also work with other machines that can take 12VDC, including PR.
ISTR that it was OMMOHY who pointed out here a while back (and it's in the user's manual) that De Vilbiss machines include the circuitry to implement a UPS if you have both AC and DC power plugged in, so that's a plus for use at home. OTOH, the automatic switch to DC will disable the heater for the duration, so that might wake you up or give you bad dreams even though there's no audible power-loss alarm as there is with most UPSes.
However and off-topic, having used both DV and Resmed for many months each at this point, I have to say that Resmed's algorithms beat the hell out of DV's, and I've come to appreciate that, so the only brand I recommend for comfortable & uninterrupted sleep is Resmed. I'm an anti-fan of Philips Respironics for other reasons including that company's lockout-with-PIN dirty tricks (the patient is not the customer; the patient is the enemy).
How this exercise in creative shopping got started was that I've been super-disgusted with all four of the available portable/travel CPAP machines, I refuse to buy any of them, and therefore I'm stuck with what I've got (full-size machines) both at home and at large.
Here are some further items of trivia learned while browsing & reading:
- The standard first step in psyching yourself down for this, if you'll need to use a lightweight battery, is to forget about the humidifier heater and the heated hose: get over it! In eschewing (I've always wanted to use that word) the humidifier entirely, I have learned to occasionally put up with a very minor nosebleed, from all that dry air, just after waking up.
- With the Gissaral, before plugging in the DC-out cable, be sure to switch the 12V/15V output to 12V by pressing the button a couple of times until the LEDs go from green to red. Green = 15V (default); red = 12V. You have to do this every time you use the damned thing, so that's a minor gotcha. It could be worse than minor if you forget to switch it and thereby let some magic smoke out, so that's another reason (besides the lack of 12V charging) to look for a battery that's better than the Gissaral.
- With a Resmed-compatible converter box, you need to give the converter its DC power feed before plugging the 24V output into the CPAP machine, otherwise it won't work and the machine will play dead. I assume that must be FAQ #1 for all of those Resmed-handshake products.
- Of course, use a voltmeter to check the voltage & polarity before plugging together a home-brewed setup for the first time, and compare those with what your machine and the 12-to-24 converter are expecting, and modify your cables & connectors if necessary.
- Some power cables with 5.5x2.5mm plugs on both ends are foolishly advertised by clueless sellers as also fitting 5.5x2.1mm jacks just because the outer diameters are the same, but I don't recommend ever using that, because the center connection at the 2.1 end will be intermittent and flaky. Go for an actual 2.5-to-2.1 cable. Otherwise you can kluge one together from a same-connector cable and a different-connector plug-and-jack attachment, for instance "Longdex DC Power Adapter 5.5x2.1mm Female Jack to 5.5x2.5mm Male Plug" (Az search).
- I considered and rejected the Talentcell YB12011000, 132 Wh, 1.5 pounds, $65 ... rejected only because the manufacturer's description says that to extend the life of the battery, it's designed to use a slow charge: 10 hours! Maybe OK for use in a motor vehicle with all-day driving.
- Also rejected was the well-known Maxoak or Poweroak K2, $100 to $140, advertised as 50 Ah (185 Wh?), also sold re-badged as GBTiger and Renogy among others. For me, it's too heavy, about 3 pounds. Except for the weight, that product looks good because of its high capacity.
- The XTPower MP-50000, 195 Wh, $150, 3 pounds, is also overkill for me, but probably useful to many other CPAP users. That's the one I would go for if weight & size & cost were not so important to me.
- The XTPower XT-20000QC2 at $80 is great except that its capacity is only about 75 Wh (as is obvious from the 20000 mAh number in the product name). I wish there were a midrange XTPower model, 35000 mAh.
- There are many other makes & models of "power bank" that have only 5V USB-jack outputs and are therefore no good for us.
- Engine-starting batteries like the Micro-Start XP-1 (and many similar) are also not appropriate for CPAP use.
- The Medistrom Pilot-24, besides being overpriced, uses the Resmed machine's heavy power brick for charging ... another situation where it's not a big deal as long as you're using a motor vehicle to carry everything around.
- The Resmed model # 37297 12-to-24V converter for the A10 and S9 is too bulky for my purposes and I didn't want to have to cut off the cigar-lighter plug and attach a 5.5x2.5mm plug; thus my choice of the BPS item instead, at about the same price.
- An updated edition (August 2018) of the Resmed Battery Guide is available on the Resmed web site here (PDF).
Non-commercial disclaimer: I have no affiliation with any of the manufacturers & suppliers mentioned in this post, except as an anonymous consumerdroid.
Edited to add: The old photo above of the Gissaral product has a DC-in jack labeled "16.8V/20V", but the product that I bought recently has "15V-20V" and its AC adapter puts out 15V at up to 4A.