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  • CPAP system backup/camping power

    I'm gleaning through several threads to compile this data.
    If your CPAP unit has a 12VDC power supply, great ! If you don't need the humidifier, even better, you will likely be able to lift the battery pack.

    The medical supply shops will gladly sell you a sexy Lithium battery, that will only last you two or three nights before needing recharge. (but no humidifier with them either)

    You can lug around a Group 24 Marine battery ($100) and wire a cigarette lighter to plug the CPAP automotive cord into. That will get you 3 or 4 days before you HAVE to recharge it.

    Or, I found a suitably sized Jump Start power pack (battery booster) that had a cigarette lighter on it's front panel. Uses a wall wart to recharge from AC power, and it came with a automobile charge cord to recharge from while driving. (Or I can charge it from a solar panel.)

    What you need to do, is to discover how much power the machine consumes overnight, and obtain a battery that can supply at least twice that much power for a night (only drains the battery 50%). Draining a battery more than 50% really shortens it life from hundreds of cycles, to less than a hundred.

    The math. You want to calculate power in Watt Hours. 45watts * 6 hours = 270 wh

    Look at the CPAP or it's power brick. Does it list wattage ? 3A at 12VDC ? 1A at 120VAC Volts * Amps = watts,
    so 3 * 12 = 36w * 6 hr = 216wh

    Same for batteries, a 20Ah rated battery * 12V = 240 total watt hours in it, 120 of which are useable for long lifetime. So this
    little exercise shows that your really need a 40ah battery for this CPAP machine. I got liucky, my 18ah battery will run my machine (sans humidifier) for 2 days @ 10" pressure, before I need a recharge.

    So give it a try, and see what works for you. And you can jumpstart the car with it too!
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

  • #2
    I also use jumpstarter packs for a variety of small jobs - with solar too, but have a caution for those who must rely on it functioning for CPAP duties:

    Many of these jumpstarters include USB ports, inverters and the like. The problem with that is that depending on the manufacturer's quality of design, if you overload or fry the usb or inverter, it can take out the logic board of the pack itself, rendering it a total brick. Even high-priced boutique all-in-one camping type boxes can suffer from a poor design goal. How much of the box becomes non-functional is hard to predict, but all it takes is one frustrating smoke-test out in the field where replacements may not be quick in coming.

    I guess what I'm saying is that if you are truly dependent on the CPAP working via the dc outlet, then instead of using the box's other built-in features, perhaps rely on the dc cigarette lighter jack to supply power to 12v > 5v mobile usb adapters, external small inverters etc.

    Lately when I've chosen a box for this application, I do without all the other frills for this very reason. I just basically need a box with an outlet, and of course clamps to allow for an actual jumpstart.

    Most of the time, I also do away with the wall-wart, or ignore it if it is integrated, and use either the cigarette lighter socket, or clamps themselves (with safety in mind!) to apply a quality charger to the box, like a Tecmate-Optimate, Battery-Minder or similar.

    It's just my way of reducing the possible additional points of failure when a remote CPAP machine is vital.

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    • #3
      Originally posted by PNjunction View Post
      I also use jumpstarter packs for a variety of small jobs - with solar too, but have a caution for those who must rely on it functioning for CPAP duties:

      Many of these jumpstarters include USB ports, inverters and the like. The problem with that is that depending on the manufacturer's quality of design, if you overload or fry the usb or inverter, it can take out the logic board of the pack itself, rendering it a total brick. Even high-priced boutique all-in-one camping type boxes can suffer from a poor design goal. How much of the box becomes non-functional is hard to predict, but all it takes is one frustrating smoke-test out in the field where replacements may not be quick in coming.

      I guess what I'm saying is that if you are truly dependent on the CPAP working via the dc outlet, then instead of using the box's other built-in features, perhaps rely on the dc cigarette lighter jack to supply power to 12v > 5v mobile usb adapters, external small inverters etc.

      Lately when I've chosen a box for this application, I do without all the other frills for this very reason. I just basically need a box with an outlet, and of course clamps to allow for an actual jumpstart.

      Most of the time, I also do away with the wall-wart, or ignore it if it is integrated, and use either the cigarette lighter socket, or clamps themselves (with safety in mind!) to apply a quality charger to the box, like a Tecmate-Optimate, Battery-Minder or similar.

      It's just my way of reducing the possible additional points of failure when a remote CPAP machine is vital.
      Good info to know.

      While I use a CPAP machine it is not critical for me to go a day or so without (although I do snore a little without one). But for those that really need it you do not want to lose your power source when you are out in the wild.

      So as a recommendation I would have a backup power source in case the first one (even if it was a plain jane one) fails.

      Comment


      • #4
        I just finished living off grid for 3 months with an Airsense 10. As said before the humidifier takes a lot of power and was turned off. I was near water and with normal humidity in the summer didn't miss it at all. My pressures are fairly low (8) and each night I consumed around 10AH, peak usage was about 27W. I used just a car battery from a vehicle I don't bring with me. These auto batteries are typically in the 60AH range and you don't want to use more than 80% before a recharge. Typical deep discharge/marine batteries aren't much better. I recharge with solar panels and the minimum I would recommend is 300W of panels. I found that a 400W converter used less overhead power than a 200W inverter. If clever, cut the wires to the fan which uses a lot of power. A 400W unit will run quite cool on this 30W load without heating issues.

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