CPAPtalk.com

I have always enjoyed backpacking. In the 4 years I've had my CPAP machine I have slept better but I haven't been in the mountains. Last time I checked, no manufacturer made a solar battery charger that could charge the batteries of a portable CPAP machine making it possible to use such a machine in the wilderness. Does anyone know of a portable off-the-grid CPAP unit available? Any idea where I could get a prototype made?

One big enough would be hard to pack and very costly. Jim

list of threads by search of forum. search.php?keywords=backpacking

There are an awful lot of topics to dig through in the link below, chob9.... but maybe you can find discussion about what you're looking for:

LINKS to Battery operation, camping, power outage
viewtopic.php?t=9682

There was a good little CPAP called the Everest II (made by Aeiomed) that had its own optional battery pack, but as far as I know it's no longer being manufactured.

If you want to find specific discussions about something like "solar power for CPAP backpacking", try typing that into a Google search, but add these run together words site:cpaptalk.com to what you type into the Google search box, like this:

solar power CPAP site:cpaptalk.com

Would you be willing to buy a machine specifically for backpacking? In order to keep costs down you would probably be looking at a straight CPAP (no auto, no BiPAP or etc).
A lead-acid battery will be way too heavy for backpacking. You *can*, however, build a battery pack that is light and provides a considerable amount of power by using lithium polymer batteries. These require some special handling, a certain type of charging system (could be solar charged depending on panels).

I was an avid backpacker/hiker/rock climber before a rather devastating car accident took all of that away from me. So I understand the requirements in that regard. I now fly radio controlled aircraft and several years ago made the switch from fuel planes to electric powered planes. Lithium Polymer batteries make this feasible because they are so light yet powerful.

Just off the top of my head I would think you'd need to connect several packs together to get the longevity you'd need. A "3S" pack is 3 cells connected in series. This yields 11.1 volts nominal. Probably enough to run a 12 volt cpap machine. A 3S, 8000mah pack runs about $45 and they go about a pound and a half each pack. You need to decide how much endurance you expect (run time) and then find a machine and calculate it's current draw when running to see how many packs you'd need to connect in parallel to get the endurance you desire. A 3S 4P pack would be 4 of the 3S packs connected in parallel. This would yield about 32,000mah (32 amps) and cost roughly $180 to construct.

And you'd still need a charger than can not only CHARGE lithium polymer cells, but also BALANCE them. They're hi tech. They have "balance taps" on the packs so each cell charges exactly the same within a pack.

Lots of other factors. What is your pressure requirement? A machine pushing 8cm pressure has a lower power requirement than a machine pushing 14cm pressure.
How many nights do you need as far as endurance?

Lots of calculations to do to see if this is workable, so much more information needed.

cbob99 wrote:I have always enjoyed backpacking. In the 4 years I've had my CPAP machine I have slept better but I haven't been in the mountains. Last time I checked, no manufacturer made a solar battery charger that could charge the batteries of a portable CPAP machine making it possible to use such a machine in the wilderness. Does anyone know of a portable off-the-grid CPAP unit available? Any idea where I could get a prototype made?

RE: solar battery charger... If you search on <flexible solar charger panel> there are some -albeit expensive- flexible solar panels that would travel well. Our ham radio club had an enthusiast that followed development of these. I imagine CPAP pulls less than a radio transceiver. But they would be expensive, and you'd need a battery and sunlight. It's probably more possible that it was, but cost in pocketbook and weight will still be significant.

Rolling your own lithium battery pack is a really bad idea.

Lithium batteries have a tendency to burn and release nasty toxic chemicals if not charged and used properly. It requires careful design of the charging circuit and battery pack to reduce the risk of fire. They also need safety circuits that disable the battery permanently if they get over discharged or charged wrong. They will sometimes quit on you with no warning like laptop batteries tend to do.

It's tough to do solar CPAP while backpacking. It's hard to carry enough battery, enough solar cells, and get enough hours of enough full sunlight to keep it going. If you're not staying at the same campsite every night, you can't charge your batteries while you're hiking to your new campsite.

Be careful about the manufacturer's specs on solar panels. They're usually rated for clear sky at noon with the panel oriented exactly at the sun. If you're lucky, you'll get about 4 hours equivalent charge per sunny day.

It's really easy to convince yourself it will work, but be sure to try it out at home before going camping and depending on it.

n0hardmask wrote:

cbob99 wrote:I imagine CPAP pulls less than a radio transceiver.

Ham radio backpackers usually do "QRP," which is less than 5 watts, often much less. It's also not keyed down and transmitting for that many hours a day. Even when operating, you're usually listening a lot more than you're talking.

CPAP is usually 10 watts or more and is 60 minutes an hour for 6 to 8 hours.

archangle wrote:Rolling your own lithium battery pack is a really bad idea.

Lithium batteries have a tendency to burn and release nasty toxic chemicals if not charged and used properly. It requires careful design of the charging circuit and battery pack to reduce the risk of fire. They also need safety circuits that disable the battery permanently if they get over discharged or charged wrong. They will sometimes quit on you with no warning like laptop batteries tend to do.

EDIT:** in reading this before submitting, it sounded kind of snotty. Not my intention at all. I bear absolutely no ill will or negative feelings toward archangel (who I am quoting). I am merely arguing against his viewpoint on this specific subject. No animosity involved anywhere following.... **end edit**

I'm not talking about "rolling your own" battery pack. I'm talking about purchasing manufactured series packs and simply connecting them in parallel. The balance circuitry a is built in at manufacture so no designing there. This connection type has been in practice for YEARS and works quite well for model airplanes as well as electric passenger cars. The safety of the charge circuit is built in to both the pack and the charger. No designing there either. Unless he falls off a cliff (in which case he has problems far more pressing than his battery pack... ) I doubt he'll abuse a pack as much as we do when flying combat where the planes are purposely trying to ram each other in ways that disable one plane (the ram-ee) without disabling the other plane (the ram-er ... grin).

Series/parallel packs allow us to run high-wattage motors at extremely high speeds (well over 100 mph very easily) for about 15 to 20 minutes or low wattage motors for really really long times (think scale predator drone.... lots of loiter time AND the batteries are powering a video camera in real time to a station on the ground).

ANY electronic device can "quit on you with no warning" but in my years of experience with lithium polymer battery technology I've never seen a battery (pack OR cell) simply quit working with no warning that a failure was imminent.

Lithium polymer batteries do NOT "have a tendency to burn and release nasty chemicals". Again, I'm going to use years of hands-on experience to support this. They CAN, however burn violently and release nasty chemicals (so we have a point of agreement). But then, so can any other commonly used battery technology. Ever see a lead acid battery explode? I have. NiCAD? yup. Lithium Ion (laptop batteries)? Most definitely. Happen often? Gosh no.... if it did, they'd be outlawed.

And I'm not arguing FOR doing this as I have no idea if there is sufficient power and endurance available without getting into a very costly custom battery. It does bear further investigation though as I KNOW I've seen someone put together several series packs into a parallel pack and actually run a LEAF BLOWER in his yard. So there is a considerable amount of power available. Enough to run a CPAP for 8 hours? I'm certain it's possible, just not certain where you'd end up with weight.

I'm not against lithium batteries. I just think it's important for people to understand their limitations and risks. I sit with my lithium battery powered laptop in my lap a lot of the time. However, if it starts getting hot, I'm going to very quickly get away from it and if it starts spitting flame, I'm going to be real careful not to breathe any of the fumes.

I have 2 lithium drill batteries and 4 lithium laptop batteries. One laptop battery still works, the other 5 batteries are dead. Most of them simply wouldn't work any more one day. The only "abuse" any of them had was going a few months without being charged. Quite a few long term laptop users say they get a year or two out of most laptop batteries.

Many lithium batteries DO have a tendency to burst into flames if you charge/discharge them wrong. Because of this, manufacturers usually design electronic circuits that monitor the charge and discharge cycles. They can detect some warning signs that the battery is getting dangerous and will "blow an internal fuse" and shut down the battery where it will no longer accept a charge. With this kind of circuit, lithium battery packs are a lot less likely to burn.

More than 4 million Sony lithium laptop batteries were recalled in 2006 because of fire hazard. I believe that Sony changed the charging circuitry later to make this less likely.

The FAA says "Effective January 1, 2008, you may not pack spare lithium batteries in your checked baggage."

Google or Youtube "lithium battery fire" for a lot of scary videos.

Lithium batteries are considerably more fire prone than most other batteries because lithium itself is more flammable than other battery material. Lead, nickel, and cadmium don't usually burn. Other batteries may produce hydrogen which will burn, but they can't contain enough hydrogen gas to make a big fire or explosion, but they can build up gas pressure and make a big bang, spraying acid around.

Manufacturers do a lot to try and reduce the flame/explosion risk, but it's still there to some extent.

Here is a MSDS for a lithium ion battery. Note that hydrogen fluoride is one of the possible chemicals released. Hydrogen fluoride rapidly turns into hydrofluoric acid when it contacts humans. Hydrofluoric acid is particularly nasty because once you get it on you, even if you wash it off, it penetrates tissue and may do internal damage hours later.

Here is the story with pictures of an explosion of a flashlight with rechargeable lithium batteries. This did NOT have a professionally designed battery pack, it had individual rechargeable lithium cells.

As I said before, I'm not that worried about commercially available lithium battery packs. They're a lot like gasoline. I understand that the gas tank in my car can become extremely hazardous. If it catches on fire or develops a serious leak, I'm getting the heck out of there. I'm not going to try to "roll my own" gas tank for my car. I'm careful where I store gasoline around the home.

archangle,

ok... #1 I think we're talking about 2 different types of lithium batteries. Your reference to laptop batteries and that flashlight thing are lithium ION batteries. The ones I'm talking about are lithium POLYMER batteries. Lithium polymer is where the development dollars have been going. Lithium ION is like Dark Ages technology by comparison. The lithium ion cells use a liquid electrolyte where the lithium polymers use a dry electrolyte with some inert gel added. They are so much safer than lithium ion that they don't require the hard shell which also makes them considerably lighter.

Lithium ION cells burn because they can't tolerate high discharge rates. They are, in simple terms, "rather touchy". The lithium ion class can only be discharged at 1C (C=capacity) whereas mainstream lithium polymers can discharge at 30C and can go to 40C discharge rates for short bursts. Lithium ION cells can experience catastrophic failure due to a bad charge or discharge. Lithium polymers typically only fail catastrophically if they they are physically damaged (punctured or crushed).

I have a 3S 2200mah pack running a brushless electric motor and powering a plane weighing about 2 pounds to speeds over 85 miles an hour easily. With a 6x4e prop it's pulling 19.5 amps at 11.1 volts or just over 200 watts. This is with a very small 3S (3 cells connected in series = 3S. Each cell is 3.7volts. 3x3.7-=11.1volts) battery weighing 6.5 ounces (180 grams)

See what I mean about bang for the buck? Lithium polymer batteries have vastly more capacity than lithium ion and they are far lighter in weight (hence the airplane and airborne video applications).

So.... I might have jumped the gun and maybe we don't disagree after all. Maybe we're just talking about 2 different technologies that sound similar?

I too have this same dilemma. My research has persuaded me to look into one of these for my ventures: http://www.mytranscend.com/pages/WhatisTranscend63/


The problem with PV solar cells is that they are highly inefficient. The most efficient cells that are commonly available, are the monocrystalline cells. To charge a battery large enough to endure several days would need a very large cell array, something along the lines of: http://www.goalzero.com/shop/p/64/Extre ... e-Kit/1:3/ , in fact, ou would probably need 2 of those panels.


Just my 2 cents

yardbird wrote: Maybe we're just talking about 2 different technologies that sound similar?

Lithium polymer batteries were supposed to be a lot safer than lithium ion. I've been hearing a lot of reports that lithium ion batteries do still suffer from the same problems. Maybe they don't suffer quite as much. I'm on candlepower forums, where there are a lot of guys who play with batteries a lot for flashlight applications and some of those guys really know what they're talking about.

There is also a LOT of difference between different battery manufacturers. Unfortunately, it's not necessarily the more expensive, big name brands, that are the best.

By the way, the new LSD (Low Self Discharge) Nickel Metal Hydride (NiMH) batteries are enormously better than the old NiMH batteries. They actually hold a charge for quite a long time. Eneloops by Sanyo are the primo brand, and there are some others that are pretty good as well.