Battery powered CPAP help

Discussion in 'The Projects Forum' started by MrJojo, Feb 11, 2013.

  1. MrJojo

    Thread Starter Member

    Jan 23, 2013
    45
    0
    Hello all,

    I have sleep apnea and require a CPAP to sleep at night. I have a power cord which goes from my CPAP to a wall outlet. This works great. However, I have started camping with my friends this recent year and I am unable to bring my CPAP with me on said trips. I want to create a battery operated adapter which can power my CPAP roughly 6-7 hours. I looked at the power cord converter and it takes wall power AC (120V I believe) and converts it to 12V @ 5A. I've been looking around and found that alkaline D batteries have a 12-18 Ah battery life (http://en.wikipedia.org/wiki/D_battery). They output at 1.5 Volts. I understand that putting batteries in series increases the voltage, meaning 2 batteries will give me 3 Volts. Therefore, if I put 8 D batteries in series, that gives me the 12 Volts I am looking for. I believe this to work, but I can only get ~3 hours of battery life. I could put 2 stings of 12V D batteries in series to get 24-36 Ah out, but that seems extremely inefficient and it will only give me 5-7 hours of operation. Does anyone have a better solution?

    Thanks,
    Matt
     
  2. #12

    Expert

    Nov 30, 2010
    16,321
    6,818
    Sealed lead-acid battery, also called AGM (Absorbent Glass Mat), or a plain old car battery, or a deep cycle marine battery.

    Edit: I take no responsibility for your choice to use a different power supply than the one that was provided by the manufacturer.

    Better, Papa?
     
    Last edited: Feb 11, 2013
  3. Papabravo

    Expert

    Feb 24, 2006
    10,148
    1,791
    Should we be giving advice on the operation of a MEDICAL device? The failure of which could have serious adverse consequences, and absolve the manufacturer of liability. What is our exposure if the advice turns out badly.
     
  4. tshuck

    Well-Known Member

    Oct 18, 2012
    3,531
    675
    You guys are good, the AAC disclaimer's got you covered:
     
    #12 likes this.
  5. bmxerds

    New Member

    Sep 4, 2012
    16
    0
    If you are going to use a 12v battery, your best bet is to use a deep cycle marine battery because they are capable of Being discharge heavily unlike car batteries which are designed to give a lot of power for a brief moment.
     
  6. MrJojo

    Thread Starter Member

    Jan 23, 2013
    45
    0
    @Papabravo
    I understand the risk, but a CPAP is basically something that outputs humid air at a constant pressure. If I don't use it, I don't go into REM sleep, meaning I wake up feeling like a zombie.

    @#12 and bmxerds
    I'm looking into the deep cycle marine batteries, thank you for the advice.

    Matt
     
  7. paulktreg

    Distinguished Member

    Jun 2, 2008
    612
    120
    CPAP devices don't pull enough current to warrant the use of deep cycle marine batteries and you'll probably find the OEM battery packs use something from the Yuasa NP series (or equivalent) although there's probably protection circuitry built in to prevent deep discharge. What make of CPAP do you have and I'll try and find out what the manufacturer uses if you like?
     
  8. MrChips

    Moderator

    Oct 2, 2009
    12,449
    3,363
    Are you tent camping or trailer camping? My tent trailer has a 12V deep cycle battery for stand alone power. It also has a 12V to 120VAC inverter. Hence I can use it either way.

    Let me know which CPAP model you are using and how effective it is.
    I have to go to the sleep clinic and get a prescription for the same thing.
     
  9. #12

    Expert

    Nov 30, 2010
    16,321
    6,818
    Somehow, I feel lucky that I breath all by myself at night.
     
  10. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,392
    1,606
    MY doctor (a sleep specialist) has assured me the only way to injure someone with a CPAP machine is to hit them over the head with one. Running it on an improper voltage may damage the (very expensive) machine itself but should not harm the user.

    My Respironics CPAP machine has a wall wart device that outputs 12 volts at 4.16 amps, and assuming the CPAP needs all of that (an over estimate) an 8 hour rest needs 33.3 amp-hours daily. Assuming I could recharge it daily that means I'd but a 12V deep discharge 100AH battery minimum.

    That's just for the air. The humidifier has a separate power input for the heater I did not investigate.

    That battery is one pretty heavy sucker to carry into the woods, even assuming the seal doesn't break and melt your back pack.

    I would have to break the circuit and actually measure the current consumed, something I am not going to do with a machine I depend on so much.
     
  11. wayneh

    Expert

    Sep 9, 2010
    12,145
    3,055
    As #12 suggested in post #2, I'd go with a deep-cycle lead-acid battery. Think trolling motor battery. Laptop batteries have a higher power density (on volume or weight) but they are more expensive and more easily damaged by deep discharge, and harder to charge properly. Lead-acid is heavy but much more forgiving.
     
  12. GRNDPNDR

    Member

    Mar 1, 2012
    435
    7

    they also tend to suffer from thermal runaway.
     
  13. MrJojo

    Thread Starter Member

    Jan 23, 2013
    45
    0
    I have this http://bipapst.respironics.com/Specifications.asp. I was looking around the Philips site and I stumbled onto CPAPs on the go (http://www.healthcare.philips.com/main/homehealth/respiratory_care/evergo/default.wpd). The main thing I've been worrying about is damaging my CPAP and not having it for use every night.

    Also, I go tent camping with friends.

    EDIT: Also, when I say camping, I don't mean hiking into the woods a few miles. I mean we go to a camp site without electricity and hike about 1 mile in, tops. Basically, we just head out and get away from the real world for a weekend.

    Thanks,
    Matt
     
    Last edited: Feb 12, 2013
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