Battery operated CPAP--which machine uses least power?

newguy · Post by **newguy** » Sat Jul 15, 2006 6:00 pm

Have been trying to figure out which CPAP uses the least power, so I can get a smallish AGM battery to run it for 4-5 days of camping use. I use 6 cm straight CPAP and would use it w/o humidifier.

So far, it seems that the ResMed S8 Escape is the lowest--as it uses just 0.80 amps per hour at 6 cm. If I calculate right, that would allow a 40 amp hour AGM battery at about 30 lbs. to operate for 4 or so days. Are there any other machines that can match or beat this?

One thing I do not understand is that Respironics offers a lead-acid battery pack that weights only 13 lbs. and supposedly powers an M series Pro for 26 hours (so 3 nights)--how can that be possible?? I don't see an amp rating for this battery pack, so don't know whether to believe it?? Anyone have direct experience camping with this?

Guest · Post by **Guest** » Sat Jul 15, 2006 10:01 pm

just go to HomeDepot in the light fixture section, look for those Emergency EXIT lights on the shelf they will have those Gell Cell batteries, about $50 a pop. If you want it to last longer buy 2 batteries and put them in parallel. If you need 24VDC, put them in series.

Then go to Kragen or Checkers and over in the battery cable section is a like a 12x12" solar panel hanging on the wall. Go down to Radio Shack and get a power plug that fits your machine, make up the wires to connect to the machine.

During the day, connect the solar panel to the batteries to recharge them. You can easily put it all in a backpack. Total cost is about $150.

Then TRY the thing before you go so you know exactly how many days it is going to work for you.

jkeene · Post by **jkeene** » Sun Jul 16, 2006 7:10 am

Say Guest, how about you login, and post a reply with some calculations behind it. I wouldn't want someone using your rather vague suggestions to find themselves gasping for breath after getting only a few hours of use from the lashup you've loosely described.

Ok?

Goofproof · Post by **Goofproof** » Sun Jul 16, 2006 6:53 pm

And being $150, poorer and out of breath isn't good. A Solar Cell to recharge enough power to run CPAP, will cost over $150 and it won't fit in a back pack, that kind of solar cell setup will only trickle charge, Now if you get one of those that run warning sign on the highway you would be in business. Jim

Guest · Post by **Guest** » Mon Jul 17, 2006 12:29 am

jkeene wrote:Say Guest, how about you login, and post a reply with some calculations behind it. I wouldn't want someone using your rather vague suggestions to find themselves gasping for breath after getting only a few hours of use from the lashup you've loosely described.

Ok?

you and plumbers butt should stick to purchasing yours already made up, it is over your head to figure it out.

sox · Post by **sox** » Mon Jul 17, 2006 7:40 am

Lets play nice:o) I found a link from my friends at fluwiki (who also have a thread going on how to power a battery when you have no power) I did not take any of their post but did bring back a link to some guys website who is working on using solar panels--of course I did not read it yet but thought some of you tech folks might be interested in what he is doing.

http://mtoal.dyndns.org/solar/

Maybe you have seen it. maybe the guy post on this site?
Sally

sox · Post by **sox** » Mon Jul 17, 2006 7:43 am

Not exactly sure how he takes it camping....I will look around fluwiki and see if I can find some more practical ideas.

Guest · Post by **Guest** » Mon Jul 17, 2006 9:36 am

newguy,

The power consumption ratings on the my Respironics RemStar AUTO are waaaay high compared with "actual" usage under normal conditions. They reflect some kind of MAXIMUM values based on (???) not sure what exactly, but probably everything operating at their outer limits. Those ratings are not useful for estimating actual power consumption under normal conditions. I learned this when I began using a power-consumption recording device called a KILL-A-WATT. The ACTUAL power consumed is a tiny fraction of the stated rated value. Here's a thread on that topic:

viewtopic.php?p=76089&highlight=killawatt#76089

I agree with GUEST, the real test would be empirical. Whatever setup you end up with, try it and see how long it lasts. Be aware that 8 cm is not 8 cm. To maintain 8 cm pressure, the power consumption varies widely whether it is blowing through an empty mask (without your face in it), or whether your face IS in it, and whether you're inhaling or exhaling, etc.

Also be aware that the total rated energy of a gel-cell may not be available for it's intended purpose, as there is generally a voltage drop over the use-cycle, which may not be up to the task, and render it useless sooner than a back-of-the-envelope calculation might suggest.

I have also used a UPS power supply (intended for computers) which has a lead gel cell inside. That lasted several nights, but I can't remember how many hours of actual usage that represents. The configuration guest was suggesting is more or less THAT, not counting the solar recharging system. My experience with solar is that it can be disappointingly slow unless you are planning to carry a fairly large solar panel. I also can't imagine a backpacker staying in one place long enough to charge a battery. (I'm having visions of a hiker with solar panel, keeping it somewhat aligned to the sun. Ok, leave it at base camp. But good for a laugh.)

Back to the future: I think the ideal backpack power supply would be a fuel cell, just pour in another few cc's of methanol/isopropanol/vodka or whatever is available. Those already exist. But the technology is not mature, nor cheap. Won't be long. http://www.automotivedesignline.com/173400611

-Ric

~~~~~
(guest, "plumbers-butt", LOL !! Sorry goofy, that was funny!)

Ric · Post by **Ric** » Mon Jul 17, 2006 9:39 am

ooooops, t'was aye, guested.

-Ric

Goofproof · Post by **Goofproof** » Mon Jul 17, 2006 10:04 am

Sox, fine link, it kind of follows what I said, $900 in solar cells, out of my leauge. A little big for backpacking, maybe if he took up para-sailing and strapped them on just right? Could even add a motor and a prop for long trips .

I'm soo.. mis-understood, that's not a sink, it's a computer, the crack is optional. Jim

I sure would like to have a six pack of thoes solar cells to play with, but as I said, not economical. It's amazing that as long as Solar Cell Tech has been around it hasn't become cheap enough to be useful. I guess when you are competing with the fossil fuel giants, you get stepped on often.

Too bad, at $29.95 for those panels instead of $450, I think I could sell a few.

newguy · Post by **newguy** » Mon Jul 17, 2006 4:51 pm

Well, the reason to estimate the darn amperage draw for a machine from a rating or other people's experience is that I can't possibly buy a bunch of machines and do the empirical testing myself using KILL-O-WATT. So, if you have done that, please post the estimated usage here for your particular machine, as I find very little information at all about this anywhere.

I probably should have made it clear that in my case I would be car camping, not backpacking, but I don't have a big RV, so need to keep size and weight to a minimum. Thus, the need for the smallest possible battery.

The guy with the solar panels and batteries has one solution for the battery charging, but it's a big, bulky version. I've thought about this a bit too. But, it seems that for my particular planned usage in a car camping situation, it would be easier to be able to charge the battery using the cigarette lighter during a drive or just wait until I get back home. One option I've found for a battery has been mentioned by others--Xantrex Powerpacks. These are nice because they have both AC and 12 volt DC outlets, include a sealed AGM battery, and can also do nice things like start a dead car battery, and they have a connector that allows you to plug them into your car's cigarette lighter.

The Xantrex Powerpack I looked at for my particular configuration is the 600HD, which has a 28 amp hour battery (maybe enough for 3 nights with a ResMed S8 escape at 0.8 amps per hour rated draw). It's 30 lbs, but has a handle so you could move it, even into a tent. Seems to be available for about $160 at buy.com with shipping included. Supposedly recharges in 4 hours via a cigarette lighter (while driving) or 30ish hours at home via AC. Anyhow, it could simply be a matter of charging the Xantrex at home, throwing it in the trunk of the car, then running the CPAP off it for 3 nights before returning home to recharge it. Thus, 3 nights car camping would be easy.

For longer car camping, in theory the Xantrex 600HD could also be charged in about 12 hours in full sun via a plug-in solar panel--the manual says a panel could be rated at no more than 30 watts or 2.5 amps output at 12 volts (about $300 to buy one), but a plus is that it does not require a regulator. Thus, the system in theory would be much smaller and cheaper than that fellow with two 80 watt solar panels and big Trojan batteries and a regulator has. In theory, one could stay out camping for long periods, since it seems likely that 12 hours of sun would occur in an average 3 day period. But, whether all this would really work is guesswork, in part because of this uncertainty about how much power the CPAP would really draw.

That information--the actual or rated draw of these machines seems to be the key information, since it determines the size of the needed battery and solar panels. Please pass along any actual info you might have about current usage...

Of course, one can solve the power problem by going with the biggest Powerpack, which has 60 amp hours and could run the CPAP for quite a few days, but it's very heavy and has wheels!

birdshell · Post by **birdshell** » Mon Jul 17, 2006 5:03 pm

I know I live in the hotbed of auto development--but there is no one here to ask:

Why does it take less time to charge a device via the car cigarette lighter than with AC at home?

It seems counter-intuitive.

Just an inquiring mind who would like to know....

wolftracker · Post by **wolftracker** » Mon Jul 17, 2006 5:12 pm

http://keenzo.com/showproduct.asp?ref=GBA&ID=703167

Goofproof · Post by **Goofproof** » Mon Jul 17, 2006 5:28 pm

[quote="birdshell"]I know I live in the hotbed of auto development--but there is no one here to ask:

Why does it take less time to charge a device via the car cigarette lighter than with AC at home?

It seems counter-intuitive.

Just an inquiring mind who would like to know....

birdshell · Post by **birdshell** » Mon Jul 17, 2006 5:48 pm

Thanks for the explanation. One more question:

Don't chargers for the cigarette lighters (such as for cell phones) have a device to avoid the overcharging problem?

And why is the home system a trickle charger? Is it because of the batteries not being exhausted as fully at home?

Thanks again, electrical experts.

Battery operated CPAP--which machine uses least power?

Battery operated CPAP--which machine uses least power?

ooooops

The Xantrex Powerpack and solar panels

Off Topic

is this cheapper

Re: Off Topic

Car chargers vs. Home