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Old 10-23-2015, 01:09 AM   #1
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A rookie question

I am a new motor home owner. 2007 Country Coach. My wife and I both use CPAP machines and I've noticed on Amazon that there are 9volt adapter cords for them. My question is this:could I run my cpap all night, with the generator NOT running, without running down my batteries significantly? We were recently at a place with no shore power, plus no generators allowed after 10:00 pm. I know there are CPAPbattery packs, but they're very expensive. Can some of you please enlighten me?

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Old 10-23-2015, 04:44 AM   #2
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I use mine on a 12volt adapter cable frequently. Besure to check your CPAP supplier website to order the correct one. Not only for plug size but amp rating also. With humidifier you can draw up to 7amps, without only 3 to 4. All night? Depends on your batteries. I would think in general if nothing else and only one it would be marginal, two OK, and4 or more plenty.
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Old 10-23-2015, 05:01 AM   #3
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A rookie question

For my S9 autoset machine, this chart from ResMed shows how big a battery you need. This chart is WITHOUT heated humidification. Be sure you use a 12 volt adapter....if you run either a portable inverter or the big one in the RV to supply 110volts, the battery in the RV will run down much quicker. There are inefficiencies in converting the battery power 12v --> 110v and then again at the CPAP from 110v --> 12v.

For your reference, a 12-18 amp/hour battery is what is in those portable "jump starter" boxes. One group 31 sized RV battery is approx 100 amp/hours

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Old 10-23-2015, 05:08 AM   #4
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One of these would run a modern CPAP approx 8 hours on a charge (using the 12 volt adapter)

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Old 10-23-2015, 05:45 AM   #5
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Many CPAP and BiPAP machines actually run on 12 volts or less. The big power supply that plugs into 110V simply converts the power. Look closely at the specs of your machine and maybe you are lucky. Some require a special cord to connect to 12V.

My Phillips BiPAP is connected directly to my 12V house power/battery. I made my own cord as the connectors are standard. I do not use the humidifier. As a full-timer, mine runs off the battery bank nearly every night, I am rarely connected to shore power.

The answer to your question depends on what you have for a battery bank and how much power your two CPAPs use. Probably yes.
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Old 10-23-2015, 06:58 AM   #6
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I run my CPAP(s) with the optional 12V cord and battery usage is minimal. You may want to upgrade the house battery(s) if they are light weights or not full deep cycle.
I wired a 12v plug from the reading light wires and mounted it to the fascia above the bed.
I experimented with the set up in my driveway before going on a trip. Previously, I had tried a 300w inverter and found it used more battery power, so I found the 12v power cords online.
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Old 10-23-2015, 07:00 AM   #7
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Originally Posted by pasdad1 View Post
One of these would run a modern CPAP approx 8 hours on a charge (using the 12 volt adapter)

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I used just that with an inverter the first time I dry camped. It lasted all the way through the first night and died about 5 hours into the second night. I think I could have gotten 3 nights with a 12v cord, but suspect running the battery dead my have shortened the life of the unit as I started leaving it at the ranger station for recharge but it never lasted the night after that.
A 35AH deep cycle battery would be a much better choice.
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Old 10-23-2015, 09:50 AM   #8
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Everything below was with the humidifier turned off.

I have a meter called a Kill-a-Watt. I used it to measure how much energy my CPAP used for eight hours of sleep, and then I knew what I would need, as a minimum, to run the machine all night. I needed minimum sixty amp/hrs to run the CPAP without damaging the battery from overly deep discharge. I ended up with a group 24 battery, but I believe in overkill and using it for other things, so the battery was much more than I needed, but I knew it would run the CPAP for two nights. if I used it for nothing else.

My TT has two group twenty four batteries, so I know I'm good for the CPAP all night, even two, if I conserve energy well.

I now recharge my house batteries with a charger that puts out more than 13.6 volts for bulk charging the batteries, and they last longer than only charged by the WFCO converter/charger that only charges at about 13.5 volts. I'm trying to take care of my batteries so they can take care of me.
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Old 10-23-2015, 12:11 PM   #9
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I use my CPAP off the 12 V inverter and it uses less than 0.2 V. per night. I have appx 400 Amp Hours of capacity in my battery system.
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Old 11-04-2015, 03:41 PM   #10
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I have a 2004 Country Coach Allure it has 2 8D house batteries I use the inverter to power the CPAP, I charge the batteries with the generator and portable solar panels 160 watt, which cut down on running the generator.
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Old 11-10-2015, 07:52 PM   #11
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I've found that my Philips Respironics CPAP machine, set to 7cm H20 and with the humidifier running on the 3 of 5 setting, draws about 1 amp on a continuous basis. The startup current is about 4 amps until the water in the humidifier tank gets up to temperature. After about five minutes the current drops back to about an amp. Apparently, they don't run the heater continuously, only long enough to maintain the temperature once it has been reached. I've checked the watt-hour draw overnight and it typically comes up to about 110WH using the AC power supply. This corresponds pretty closely with a 1 Amp load on a 12 Volt circuit for 9 hours. Powering the unit directly from 12V DC should be slightly more efficient as the losses from the switching power supply would be eliminated.

The figures shown for the AH size of the battery in the table above is slightly low as a .89A load for 8 hours would use 7.12AH. Sticking to a practice of not discharging the battery more than 50%, a 15AH battery would be more in order. In any case a typical house battery (bank) should have no problem accommodating a CPAP machine, if the other loads in the RV are not using up the charge of the battery.
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Old 11-12-2015, 07:59 AM   #12
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I don't know about CPAP machines but the other respondents have provide what looks to be some very good advice.
I do know something about generators though. If you do have to run a gen all night (as I have multiple times) be aware of Carbon Monoxide). Use a generator stack , no matter where you are and have a good CO detector.

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