Night time 120 v need

flyfisheraa573

New member
A few years ago, I was diagnosed with sleep apnea...all is good now, but every night I sleep with a CPAP.

Unfortunately, it has cut down considerably on my camping, and quite honestly I miss it. Now I have three children and a wife that I'd like to share my love of camping with. So, my middle son and I have been kicking around the idea of a expo trailer. Now comes the question....

Is there a way that I can quietly (at night) get 120v to power my CPAP, while camping in a remote location?

Thank you ahead of time for any and all help.
 

flyfisheraa573

New member
It plugs into a 120v wall outlet...not sure how many amps it draws...

What I would like to do is be able to do a multi day trip...so, someone to power it at night (other than a generator) and some way to charge power source during the day.

I actually have a small 500 watt generator that I could use if need be to charge it...but if I could find a quiet solution, that'd be nice
 

048642

Adventurer
I brought two spare 12v batteries (Optima Red Tops) with me on a trip last year and an inverter with battery clips. I used the set up for four nights without any problems. I did two nights on each battery, I probably could have done all four nights on one battery, but since I had them I used them both. I also use the set up at home during power outages.


Sent from somewhere on Earth.
 

UK4X4

Expedition Leader
Invertor or 12 V power supply

look on the back of your machine for its wattage- this is usually worst case

Then look for an invertor -power supply suitable to supply just that wattage- any more and you waste power

What machine is it ? how many hours a night do you need it- is it always on ?

Google foo the datasheet and post the link- without the exact power requirements - no one can answer

can it be done - yes- how many batteries and charging requirements is the question !
http://www.cpapaustralia.com.au/shopping/resmed-dc-12v-24v-s8-model-converter-33942.html
 
Last edited:

wrcsixeight

Adventurer
12 volt Cpaps exist. That way they will not have to use a ~90% efficient inverter, and might actually be constructed with efficiency in mind. Most devices that plug into the wall are not concerned in the slightest, about how much electricity they consume. Too many people just figure to run such devices on an oversized inverter, and that a few minutes of idling the engine is enough to recharge a battery

If you can list the amp draw, we could figure out how much battery you need nightly, and how much solar to recharge it.

The few threads I have seen say they pull about 3 amps. 3 amps x 8 hours= 24 amp hours. A large healthy fully charged group 27 battery has ~ 100 amp hours, 50 of which are regularly usable, perhaps 80 if you do not care about battery longevity.

Expect 200 watts of solar to return about 65 to 80 amp hours into a battery this time of year, in a sunny environment, panels flat on the vehicle roof.
 

flyfisheraa573

New member
Awesome answers! Thank you so far for the help...that's why I love this forum!

I'll check tonight on the amp draw, and post it up tomorrow.

To answer a few questions...I use it every night. Although by looking at me, I am fairly healthy looking and only 38, I have the sleep patterns of a 80+ year old man, or so the dr says...so, I use it every night, as I got the crap scared out of me about the possibility heart attacks and strokes during sleep.

I used to tent camp when I went fly fishing, quite a bit, until I got it...only been a few times since then, and I really miss it. After I got it, w typically stayed in a cabin, and due to the cost of a cabin every trip, that lessened the amount we would go. BUT now I have kids, and am awesome wife that I want to share these things with.

Sorry for the ramble, and again thank you...I'll provide the necessary info
 

RangeBrover

Explorer
I know you said no generator but if consider getting a Honda model, they are impressively quite, and you'll barely notice it's on. Otherwise I'd go with a dual battery setup and run an extension cord from an inverter to the trailer. That way you'll have plenty of power plus it'll recharge easily during the day.
 

flyfisheraa573

New member
Okay...according to the label on my machine it says "12v (and a symbol that is a line with three dashes under it) 6.67 A)

Keep in mind it plugs into a wall outlet...

Okay for you electrical minded folks:

1) did I provide you the info that you needed?

And 2) please advise

Again, thanks for all your help!
 

wrcsixeight

Adventurer
Does the machine have a power brick inline on the power cord, or a wall wart which plugs into the wall? These transformers take 120 Vac and turn it down to a lower DC voltage. If this is the case then this can be plugged directly into a 12 volt battery, properly fused of course and double checked to make sure the polarity is correct.

.

The bad news is 6.67 amps is a lot. For 8 hours of sleep it would pull mathematically, 53.4 amp hours. A group 27 battery has 115 amp hours, and when new and fully charged could power this overnight and no go below 50%, the level at which you should try to not let the battery fall below. 6.67 amps is also near the upper limit of what a ciggy plug/ power port can handle, and only if it is wired properly with 12 awg or thicker wire.

You would need about 130 watts of solar and a sunny environment to replenish just what the Cpap consumes nightly.

6.67 amps might be the absolute max amperage it will ever pull, and it might consume less than that after started.
 

ldivinag

Adventurer
get 2 batts.

cheapy marine batts from walmart.

use your generator to recharge them during the day or get a solar setup.

i used to use a CPAP machine when i was (mis)diagnosed with SA.

i would not use an inverter since to me, that is an extra step which just burns up energy as a result of inverting. if your cpap machine has a standard plug, go to radio shack or something and just get the plug and connect or make an long cord to run from the batts to the machine.

otherwise, if it uses a weird connector, i guess, as a last resort; cut the cord coming from the cpap brick to the machine. i would use something like anderson pole connectors to connect the connector to the brick. and then when going 12 volts, just disconnect the anderson pole and create an extension cord to go from the batts that terminates also with the same anderson pole connectors...

does this make sense?
 

kevint

Adventurer
Okay...according to the label on my machine it says "12v (and a symbol that is a line with three dashes under it) 6.67 A

That is probably the maximum draw your machine would achieve with maximum treating pressure and heated humidifier. Your needs are probably much less.

Here is how I would attach your problem. I find it easiest to think in watts when we are moving back and forth between 12v, 120v and other voltages. To help get you in the ballpark I'll give an example from my CPAP. I rarely use the heated humidifier (never for camping because of the amperage draw) and my treatment pressure is 11 cm. My CPAP takes power from a transformer rated 19v. I've also seem them at 24v. Based on my particulars I've worked out that my CPAP draws on average about .53 amp at 19 volts. Here is where I convert to watts. When voltage changes, amperage changes but watts stay the same, so:

19v x .53 amp = 10 watts (at 19 volts)

since watts stay the same I can calculate,

10 watts / 12 volts = .83 amps (at 12 volts)

or

10 watts / 120 volts = .08 amps (at 120 volts)

Watts are an instantaneous measure of how much electricity is flowing at any given moment.

----

The only way to tell how many watts your machine draws at your treating pressure is to measure. There is a little device that costs about $25 called a "Kill-a-watt." You can google it and can probably find one in your home town. You plug it into a wall outlet and then plug your CPAP into the Kill-a-watt. After one night you can look at the reading on the Kill-a-watt but it might be better to let it run for a week and divide by 7 to get your daily usage. The Kill-a-watt provides a readout in kilowatt-hours (KWH) which is the amount of electricity consumed by using 1000 watts for 1 hour. In my case after 1 week it would probably say something like .42 KWH. Multiply this number by 1000 to get watt-hours (420 watt-hours) and divide by 7 days to get 60 watt-hours per night. You're almost there . . .

To get your daily requirment in Amp-hours for a 12v system then you just divide the 60 watt-hours by 12 and you get 5 amp hours per night. Multiply the daily amp-hour requirement by the number of days you want to supply power for and you know your need. Let's say you want four nights of power for your CPAP. 5 amp-hour per night x 4 days = 20 amp hours.

Now you're really almost there . . .

If you are going to use a lead-acid battery (car battery, deep cycle marine, golf-cart or jump starter) people generally recommend that you not plan to regularly draw the battery below 50% which means you should double your estimated need when sizing the battery, so in my example I would need a battery rated at about 40 amp-hours or greater.

I know that sounds complicated so if you follow this 1 week testing process and simplify all of the calculations you get:

Battery Needed (in amp-hours) = Reading from Kill-a-watt (in KWH) x 24 x number of camping nights desired

which, for my example with a 7 night test would be

.42 KWH x 24 x 4 days camping = 40 amp-hour battery needed.

Remember that if you run through an inverter you lose some efficiency so, to be save bump the estimate up by 10 to 20%. In my case at least a 50 amp hour battery is what I would be targeting. Also, it seems to me that at altitude, my CPAP works a little harder so a little extra is not a bad idea, not to mention that it's nice to have a little extra power on hand to charge a camera battery or cell phone.

All that seems overly complicated and I'm almost embarassed to post this but, at a minimum, beg, borrow or buy a Kill-a-watt, run it a week and post the result here. Any number of people can walk you forward from there.

Hope this helps. For years I only camped in state parks in the "water and electric" section so I could run an extension cord to my CPAP. Last year I bought a little tent camper and put together a battery system. Now I can camp for up to about a week anyplace I choose. Good luck.
 

Doc Foster

Adventurer
Most CPAP machines are actually 12V units, but use a power supply to run on 120v household current.
With most CPAP setups, the heated humidifiers actually draw more "juice" than the CPAP itself. Most CPAP specific battery setups will NOT power the humidifier and the CPAP, usually just the CPAP itself. If you leave your humidifier hooked up to your CPAP and just turn the humidifier setting to 0, and leave water in your humidifier chamber, you can still get some humidification without actually powering the humidifier. Older style CPAP humidifiers were just that - nonheated "pass over" humidifiers. So now you only need enough 12v power for your CPAP and can still get some humidification. If you look carefully, most CPAP batteries only provide an adequate charge for one night, maybe two depending upon your CPAP pressure and obviously how long you sleep.
 

chuppie

Observer
I have M Series 100 Remstar by Respironics set at 9.5. I measured 1.53 amps at 12 volts using a 400 Watt Cobra Inverter. I used a Fluke Digital VOM to measure it and to confirm what my analog amp meter was showing. It draws .14 amps at 120 volts ac so true to Ohms law and the inverter efficiency , the numbers are good.

Use an small cheap inverter hooked up to you vehicle battery. I was going to build a back up battery but it turns out I could go for many days without affecting my car battery. Typical over-thinking something on my part. Just don't use the humidifier.

See my CPAP thread from a few days ago.

Regards
Rick
 

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