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Old 03-03-2015, 06:29 PM   #1
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Boondocking with a CPAP

My wife has just received her first CPAP machine so I have a question. We like to boondock. I am thinking of adding a separate battery just for a small inverter to run her CPAP machine. I am thinking of using a battery isolator so that the RV converter, and tow vehicle can charge the second battery, but nothing from the RV could draw from it EXCEPT the CPAP inverter. Anyone here wire an isolator in for two batteries? Or any other ideas to help settle the wife's fear of the battery draining while using the heater and such in the coach??

Bob & Kimi, Fuzzy Butted Daughter Penny
2012 Crossroads Cruiser CF27RLX
2000 Ram 2500
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Old 03-03-2015, 06:31 PM   #2
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Here's a link to previous threads that may assist.



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Old 03-03-2015, 06:32 PM   #3
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Thanks! Will check it out!
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Old 03-03-2015, 06:38 PM   #4
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Originally Posted by bdwillie View Post
I am thinking of adding a separate battery just for a small inverter to run her CPAP machine.
Hi Bob,

The first thing to check is whether the CPAP is 12V. Many of them are. If so, all you need is the appropriate plug wired into your 12V house system - no need for an inverter.
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Old 03-03-2015, 06:40 PM   #5
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Unfortunately, her's is a 24 volt model
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Old 03-03-2015, 08:07 PM   #6
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Originally Posted by bdwillie View Post
Unfortunately, her's is a 24 volt model
2X12V in series?

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Old 03-03-2015, 08:28 PM   #7
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There are 12 to 24 switching converters available. How much power does it draw? That is the first question for everything else.
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Old 03-03-2015, 10:26 PM   #8
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My CPAP is 120V only, an oversight on my part when I got it.

I have a 1200W inverter that I plug it into, on the 12V side I found that it draws in the 5A range when running with the humidifier on high so one battery could easily handle it overnight (5A times 8 hours = 40 amps, under the 50% point of most deep cycle batteries). I converted mine to four 6V batteries and just wired the inverter directly to the output of my battery switch.

How you patch yours in is up to you, you could do a simple switch to isolate it from the rest but you'll have to remember to flip the switch. I'm sure you could come up with an automatic setup that is powered when the converter is plugged in to shore power but if it were me I'd just add an extra battery (Or three. I love my setup.) and just wire it in.

If you have the space to go the four battery route I whole heartedly recommend it. I can spend the evening watching TV, running lights, water pump, etc, sleep through the night with my CPAP, iPad and phone charging, furnace keeping the interior 50* in 19* weather and wake up to the voltage at 12.3-12.4V or 70-80% SOC. My converter would reach float mode in less than two hours on the generator, frankly if I was miserly with my power I bet I could make two days without charging and three without the furnace going.
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Old 03-04-2015, 06:16 AM   #9
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You can buy one or two 35AH deep cycle batteries. If her CPAP is 24v, you could wire two in series on the closet floor. They are smaller & lighter than house batteries. Get the AGM type so you don't have to worry about venting. They run $65-70 on Amazon. You could also get a 30-80 amp solar kit to charge it (them with). Of course upgrading your house batteries and adding solar or generator could take the worry out of depleting your house batteries.
I used a large portable jump start battery for my first boondocking with a CPAP. It went dead the middle of the second night and needed two days on 120v to recharge. Learned my lesson on start vs deep cycle then.
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Old 03-04-2015, 07:03 AM   #10
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I have used a CPAP for the past 15 years so, after wearing out my original machine, I've had the opportunity to buy another and utilize the experience I have gained.

Has your wife tried using her CPAP without a humidifier? Some folks require one and others don't. i was provided with one when I started out but eventually I was forced to try going without it when travelling light for business. I then found that I really didn't need it. If she can go without the humidifier you can greatly reduce the power requirement as the heat element is the greatest power draw.

If finances allow you can also look at more power efficient models and accessories for travel. My pressure requirements are significant so I purchased a second portable unit for travel and it is ideal for motorhome travel. It draws very little power and can even be run from a small rechargeable li-ion battery that fits in the palm of your hand.

This is the model I have but there is another portable unit available now that is even more compact and uses a small li-ion battery. CPAP.com - Transcend Travel CPAP Machine

My full-sized 120 volt unit also works fine in our MH running off the inverter. It and the loss to the inverter show a combined draw of 3 amps.
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Old 03-04-2015, 01:32 PM   #11
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I bought a 2nd cpap(12V) just for the RV.I got a factory reconditioned from my local respritory therapist for less than half of the same model new.
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Old 03-07-2015, 03:11 AM   #12
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Wish I could use the proper terms but alas! Have used a cpap for years. Have a old one in my RV. When I had a Trailmanor I had them install a 12v cig lighter next to my bed. At some point I got a adaptor that plugs in the cig lighter and my CPAP plugs into that. Works great.
I now have a used Itasca Navion 23H and I have to use the Cig Lighter that goes with the TV power button. So I now need a 6 foot extention cord and then I plug my CPAP into that. Use same adaptor that I used in my Trailmanor. Works fine. Just have to be careful not to get my foot stuck in the cords when I take the ladder in the middle of the night. LOL

PS: Never used it two night in row. Just one night in a parking lot.

PPS: When I was given my CPAP they said I could use it any place.. I have taken it to France--England--Germany-Holland All I needed was the correct Elec Plug for the country I was in. Never had a problem.
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Old 03-07-2015, 08:52 AM   #13
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Wink Aa dedicated DC outlet works for me

If you end up using an inverter be sure that it is a Pure Sine Wave model as many CPap's can be damaged by the use of anything less. When I got my CPap about 9 months ago I ordered a 12v power cord from the manufacturer. Then I hard wired a cigarette lighter outlet directly to the house batteries (with an in line fuse), near the head of our bed.

This works well and even on nights when the furnace runs intermittently (my CPap has a humidifier), the two group 27 batteries handle the load without a problem. Always nice to have another DC outlet available as well. Works for me.

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Old 03-07-2015, 12:22 PM   #14
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There is an easier method... Get a 12 volt CPAP. Yup, they make 'em that are designed to work off automotive battery power in the event of a failure.

Next you need to knwo how much power that blower sucks overnight, Recommendation, plug it into a Kill-a-watt and ask it for watt hours.. Post results (Actually PLEASE do this I would really like to know, In fact PM me with them if you can (and post public as well) I'll do the math and tell you how much battery it needs.

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