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Old 05-16-2010   #1
cataraftgirl's Avatar
Sandy, Utah
Paddling Since: 1997
Join Date: Jun 2009
Posts: 3,120

I have a rafter friend who's snoring has progressed to mild sleep apnea. He is getting a portable CPAP machine and is trying to figure out how to use it on the river. I know of people who use them on the river, but don't know the details of how they power, recharge, and transport them. Any info would be much appreciated.

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Old 05-17-2010   #2
lhowemt's Avatar
at my house, Montana
Paddling Since: 2020
Join Date: Apr 2007
Posts: 4,347
I was just on a trip with a guy with a CPAP. I'll ask him if he'd be willing to pass on some information, and let you know.

I am a river, babe - I've got plenty of time, I don't know where I'm going, I'm just following the lines..... - "We are water" by Shaye
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Old 05-17-2010   #3
Join Date: Aug 2006
Posts: 199
I have only seen car batterys used to power these devices.
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Old 05-17-2010   #4
lhowemt's Avatar
at my house, Montana
Paddling Since: 2020
Join Date: Apr 2007
Posts: 4,347
Here's his setup:

I have a lightweight CPAP machine that is wired to operate off both 120V and 12V power. It consumes about .9 amps/hour, or about 7-8 Ah per night. I carry the CPAP, the 12V connectors and a 34 Ah sealed AGM lead-acid battery in a large Pelican case, on top of which I have mounted an 11-watt flexible solar panel. I drilled (then sealed with silicone caulk) a hole in the Peli case to connect the supply wire from the solar panel to the input leads on the battery using polarized DC connectors. Although the solar panel is insufficient, even in ideal sunlight conditions, to fully replace the amps used up each night, the daytime recharge typically extends the usable life of the battery from 3-4 nights to 6-7 nights. This is sufficient for a 5-night Middle Fork trip.
I am a river, babe - I've got plenty of time, I don't know where I'm going, I'm just following the lines..... - "We are water" by Shaye
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Old 05-17-2010   #5
Parker, Colorado
Join Date: Jun 2008
Posts: 52
Be sure you don't charge the battery while it is in a sealed case. Since even "sealed" batteries can gas while charging, it's always a good idea to have the battery in a well ventilated area while charging. The little "seals" on AGM batteries keep acid in but I think they are meant to allow gas to pass thru? This may not be an issue charging at the lower amperage the solar charger puts out, but do pop the lid if you throw it on a 120v powered high amp charger.
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Old 05-18-2010   #6
Canon City, Colorado
Paddling Since: 2000
Join Date: Apr 2006
Posts: 426
Nearly all AGM batteries are "recombinant" batteries, meaning that hydrogen and oxygen recombine back into water within the battery. While some gases can escape from an AGM, amounts are typically extremely low.

Excess voltage is what does cause gassing in batteries, not the amperage, as I understand. Even with a low amp solar panel, it can be possible to cause gassing because voltages are too high.

If you're concerned with blowing up a peli box with hydrogen, or if you just want your expensive batteries to last as long as possible, get a quality charger that adjusts the voltage as necessary depending on the level of charge and the temperature.

Also, keep your batteries cool. While cold batteries don't perform as well as warm batteries, hot batteries lead to higher gassing rates, and faster degradation of the battery.

If it were me, I wouldn't worry about the gassing, but I would use a charger to prolong battery life (and prevent gassing as a bonus), and I would use a set of wires long enough to keep the peli case out of the sun when charging with a solar panel. I'd keep the peli/battery out of the sun altogether, actually- not just when charging.
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Old 07-14-2010   #7
Albany, Oregon
Paddling Since: 1975
Join Date: Apr 2010
Posts: 3
Many Options Available

If you type "CPAP Battery" into Google, you will find many vendors and many options. I have a Respironics CPAP unit, and I ended up purchasing a Respironics battery pack online to go along with it for a little over $200. My medical providers were clueless and I had to develop understanding on my own--thank goodness for the internet. My CPAP machine (in its case) and my battery (in its case) fit together neatly into a 30 Liter dry bag.

The Respironics battery pack is entirely self-contained in a small fabric case, but it is heavy (14 lbs.) because it is a lead/acid gel battery, like a deep cycle RV/marine battery. Despite it's weight, I chose this one because of its long battery life (I have used it 5 nights without recharge) and its built in "plug-and-play" features. There are many other options out there, including a variety of lithium ion batteries that are lightweight and provide 10 to 22 hours of service, depending on their size and price. Also, there are solar recharging options, as mentioned above.

If you are a CPAP user, please be aware that you should not run the humidifier while using battery power, as the humidifier heating unit will deplete the battery much faster than if you don't use it.

While I personally think that solar photovoltaic panels are very, very cool, if I were to go on trips longer than 5 nights, I would purchase a backup battery--maybe a smaller one--and charge it before leaving, rather than try to set up a solar panel system. If you check around, I think you will find this to be less expensive and more fail-safe. I think you could readily get up to 8 nights of service from a 2-battery system. For longer trips in sunny climates, probably solar panels would make sense.

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