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Wilderness Camping Experience
After creating the long thread on the best way to take CPAP wilderness camping, I can report on my actual experience of a week in the Boundary Waters with CPAP.

First, a few preliminaries to put things in context. I have a Devillbiss Intellipap, standard edition. My pressure setting is nine. The ramp up is five minutes. My hose is unheated. On the advice of my physician, I did not use the humidifier. He does not think I need it in the summer. HOWEVER, your situation may be different, so check with your provider. If you get the thumbs up, try it for a few nights to be sure you like it.

The main finding is counter-intuitive, at least for wilderness camping: several small batteries are better than one big one. For me the ideal battery was a 3.2 pound 7.8 amp hour 12 volt sealed lead acid battery. A two-pack I bought on the net cost $34. I ended up buying three, intending to rotate them using a solar charger.

I went through a few solar chargers during home trials and never found one at a reasonable price that would charge a 12v battery. You have to go over $100. Anyone who has found and tested one that costs less please jump in. What I found were many good chargers, but all were configured for USB, which outputs considerably less than 12v and hence will not work. A few purport to output 12v, but I found they did not charge or their output was so low they were worthless.

The other reason for wanting to keep the cost of a charger under $100 was as soon as you get up to $150 or so you enter the territory of the proprietary systems sold on many web sites.

In addition to the three batteries, I rigged up my own charging unit with a surplus DC tip from a wall wart that fit the DC plug on the machine. I attached to this some connectors I insulated to prevent any inadvertent shorts in the middle of the night during a rainstorm or whatever. To this connecting cable I added a cheap digital volt meter purchased from an auction site for $5. Total cost for three batteries plus meter: about $60.

If you do do any research you will find a 24 amp hour battery will cost considerably more-- but also weigh A LOT. My three 7.8ah batteries weighed less than a 14ah I purchased as a backup. Another advantage of the smaller batteries is they pack easier. All mine went in individual waterproof bags.

You also may want to purchase a decent charger that will work with SLA batteries. This is VERY important. You cannot charge an SLA with a wall wart or many car battery chargers. Mine cost $35, but will charge a lot more than just my CPAP batteries.

What I experienced surprised me. First, using the voltmeter and charger meter I checked the new batteries and found all were under-charged. It took awhile to "top them off" which ended up being about 13.8 volts. THIS STEP IS CRUCIAL!

I decided to go without CPAP the first night for several reasons. If it did not work out I had the batteries for backup. If something serious developed, I was close enough to civilization to get out. It also gave me an idea of how I would do without CPAP in case something happened to the batteries. This "test night" is the second critical ingredient. Again, I checked with my doctor to be sure it was OK to skip one night.

After that I used the batteries. They lasted me five nights, for a total of six, good enough for a decent wilderness trip. One battery lasted two nights, the other two a little less than two. The volt meter said they drained slightly as days passed. Not a lot, but enough.

What I found, not surprisingly was that when the charge in the batteries dropped below 12v the CPAP quit. Usually 11.7 was the shutoff point. I mention this because all of us with car batteries know they will start a vehicle if a little low. Not so with CPAP.

What surprised me was how little the machine drained the batteries. I don't know if these were from an exceptional manufacturer (they do rate the highest--and are by far the lightest). A 3.4 pound 7.8ah battery could last two nights. That was all I got out of the 14ah battery from a different manufacturer that weighed 11+ pounds.

Maybe someone can explain this apparent anomaly. Checking the machine when I returned home I found it was working the entire night.

So how much did I sleep? The average was seven-plus hours. I find that is all I need. One night I slept almost nine hours.

The machine, which I packed in an old waterproof, padded camera container and the batteries survived torrential rain storms, sitting in the bottom of a canoe (of course the packs were water proof/repellant). They survived running and walking rapids, numerous portages and enough mosquitoes to pick the whole rig up and carry it away.

So what is the summary:

SLA is best due to cost/weight factor
Go with several small, light ones not one big one. In addition to weight, they make packing easier.
7.8 hours appeared to be the magic number. Larger sizes up to 14ah weigh more and cost more.
Be sure and have a voltmeter
When solar gets cheaper it will make wilderness CPAP camping feasible for weeks, not days.

Good luck to everyone venturing into the backcountry! This experience prooves you can do it for an additional cost of $60-$80. Go for it!

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Hey! Great article! Thanks!

And timely as I am looking into battery systems too, but more for at home.

In your research, did you find any solar chargers you would want to use at home vs out in the wilds? You can mention product names and even websites, just not web addresses.
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One thing you might want to note. The 13.8 volts is not the actual battery voltage but is a number related to the charging voltage and after being disconnected from the charger for a while will drop to the actual terminal voltage. For longest life the batteries should not be discharged to below 50% of capacity.
Below is a state of charge table showing the voltage that represents the state of charge.

[img][Image: battery%20voltage%20chart_zps3avhksr1.jpg][/img]

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For home I would just go with an electrical charger, much cheaper. Mine is a Schumacher Electric Specialty Lead Acid Battery 12V 6V Speed Charger SCHSC-600A. It costs $39 and is widely available.

Everything solar under $100 did not work. Battery Tender Makes a rigid panel about five feet high that puts out a healthy 15w plus it comes with monitoring and connecting equipment. However it costs $139 and weighs quite a bit. Obviously not something for a canoe or back pack. That was a big problem I forgot to mention about using solar panels: if they do not have the proper monitoring equipment they can be dangerous with SLA batteries. Why? SLA batteries build up heat when charging. If the charging device does not have the proper connections it can become literally a time bomb.

The big player in camping solar panels that are foldable appears to be Goal Zero, but a charger that would work with a 12v SLA battery will set you back $169--and I cannot tell if it has the proper monitoring for SLA. At that price you might as well go with one of the manufacturer-made kits since you know it will have all the right connectors, etc.

BTW, I learned different CPAP machines have different-sized DC jacks, just like computers and cell phones. So you need to check that when buying a solar charger. It would be nice if all these folks could just agree on a common size, but then they couldn't over-charge you for THEIR connector.
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(07-25-2015, 03:22 PM)Oldguide Wrote: Everything solar under $100 did not work...

The big player in camping solar panels that are foldable appears to be Goal Zero, but a charger that would work with a 12v SLA battery will set you back $169--

I agree with you there. Even Harbor Freight's 45-watt kit is about $190 sans coupon.

Using FlashAir W-03 SD card in machine. Access through wifi with FlashPAP or Sleep Master utilities.

I wanted to learn Binary so I enrolled in Binary 101. I seemed to have missed the first four courses. Big Grinnie

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Was wondering about the solar charging for charging the batteries when there is no house power. I'd rather not fire up a vehicle just for that.

I think I have the same charger. It can do car batteries and deep cycle, 12v and 6v.
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Most of the time I have been without house power it has never been longer than one or two days, with the exception of one blizzard. When my parents lived near the Canadian border they had a backup generator since they could be without power and snowed in for a week.

If your house power is down, CPAP probably falls down the list in terms of priorities, especially in the winter.
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Have you looked at HARBOR FREIGHT if there is one in your area or go online. The 13 Watt Briefcase Solar Charger puts out 12/24 volts. Amperage should be around 1 amp at 12 volts. For a sunny day that would provide some recharge capability. Not a lot but maybe that is enough. It is light and very portable. and around $77.00.

Reguired a controller not included. 12v setting output is 23.6v for the 24v setting it is 47.3v. A charge controller is needed for charging 12v batteries. I use a 7 amp controller HF 100 Watt Solar Charge Regulator Item # 96728 (~$25.00. I like the seamless integration between the panel and controller. Works fantastic and it folds up for storage.

Watch for sales at HF. One advantage is HF will take it back if it does not work. Post back if that works out.
It does not matter how slowly you go as long as you do not stop. --Confucius
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Thanks much for the info but I will not be trying it as the cost and weight exceed the limits I set. Add batteries to the Harbor Freight solar and you are up around $150-200.

Since the camping season is going to be upon us soon let me reiterate the basic points of my original post. Most important is that you can do true wilderness CPAP camping for about $80. Here again is how I did it:

1) The key is to go with SMALLER SLA batteries, NOT larger ones.

2) 7.8 amp hour batteries seemed the best for weight and efficiency. Three got me five nights of sleep at 7 hours per night.

3) Buy a small portable amp meter (about $1.00) to monitor your batteries.

4) Rig up a connecting harness from battery to the CPAP. You will need to know the size of your DC jack to do this. Consult your manufacturer specs. Add the DC jack to alligator clips and you have your charger.

5) If you don't have one get a small charger suitable for SLA batteries. The one I used is listed above.

6) Using the charger and meter top off your batteries. If your charger does not have a regulator monitor the heat of your batteries VERY closely.

As for the Harbor Freight, it requires a separate regulator. That pushes the cost over my $100 limit. You might also check the reviews. It takes up to EIGHT hours to charge a battery according to one reviewer. That means it is only acceptable for base camping not backpacking or canoeing.

The manual is very vague. One line made me extremely skeptical. It mentioned being very careful about the glass cover. The panel is also sold by Amazon for $146. However, Amazon was more upfront about specs. Weight could be an issue, because Amazon gives contradictory numbers. In one place it said the weight is 13 POUNDS; in another 2 Pounds. Thirteen pounds would rule it out for backpacking or canoeing. Having watched videos of this the thirteen seems more likely. It is big and rigid. Packing it would be interesting, especially if the glass is an issue.

Reviewers on another forum were skeptical of this item. See: https://www.solarpaneltalk.com/forum/off...olar-panel

If you are still interested in this charger do a search for Thunderbolt Magnum 68750, you can probably beat the Harbor Freight price. A fair number of these on Craig's List.

Take care and have a great summer.

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Yes OldGuide, I would agree with your comments about the HF solar unit. My son uses it as a trickle charger for his boat battery at the dock because there is not an electric outlet at his dock. It works ok for that but you are right the output is only about 500 ma in bright sun ~13 watts. The controller is required to change the voltage to 12v from 24v. I have not weighted it but I don't it is 13 lbs.

I personnal don't camp so the comment was for a different use.

It does not matter how slowly you go as long as you do not stop. --Confucius
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