My backpacking/ camping CPAP battery solution.

[MagicPaddler]

I have been working on helping a friend with a CPAP replace his old batteries. He has a ResMed S9 Elite running on a ResMed converter which operates on a battery pack. The battery pack is made up of 3 series sets of 4 parallel 18650s (3S4P). The battery pack and Converter have mating automobile cigarette lighter connectors. The Converter lists the input voltage as 12 to 24 volts. The voltage of 3 li-Ion cells in series put out from 12 volts down to 9 volts. So I wondered if the converter would operate more efficiently if it was operated on voltage in the range it was designed to operate on. If I put 4 cells in series the voltage would be in the range that the converter was designed to run on. I hooked a lab power supply through a amp meter and added a vote meter after the amp meter. I took data from 9 volts through 17 volts. The S9 needs to be in use to operate so my friend wore it. I set my meter to averaging to average out the changes but the meter averaging is met to take out short spikes and would take out 10 Hz variations but he was not breathing at 10 Hz. So data was real hard to get any accuracy on. But I can see that the power used at higher voltages was not lower than power used at lower voltages. So putting 4 cells in series is not better than 3 in series. S9WatsToVoltage.jpg

[BigE94]

These might be a great solution if you know what you're doing. They could be a terrible choice if you don't. If you continue discharging a LiPo battery beyond it's limit, it can (and often does) overtheat enough to catch fire, destroying a lot more than just the battery. I don't have time to go into the details at the moment, but if anyone is interested in this it could be done safely IF you have the right gear and understand how it works.

- James

Agreed. I have looked at a lot of batter options, DIY and otherwise. Much safer and cheaper to purchase an off the shelf solution. Amazon has been a godsend for testing purposes. I found a solution and bought two.

[BigE94]

I have been working on helping a friend with a CPAP replace his old batteries. He has a ResMed S9 Elite running on a ResMed converter which operates on a battery pack. The battery pack is made up of 3 series sets of 4 parallel 18650s (3S4P). The battery pack and Converter have mating automobile cigarette lighter connectors. The Converter lists the input voltage as 12 to 24 volts. The voltage of 3 li-Ion cells in series put out from 12 volts down to 9 volts. So I wondered if the converter would operate more efficiently if it was operated on voltage in the range it was designed to operate on. If I put 4 cells in series the voltage would be in the range that the converter was designed to run on. I hooked a lab power supply through a amp meter and added a vote meter after the amp meter. I took data from 9 volts through 17 volts. The S9 needs to be in use to operate so my friend wore it. I set my meter to averaging to average out the changes but the meter averaging is met to take out short spikes and would take out 10 Hz variations but he was not breathing at 10 Hz. So data was real hard to get any accuracy on. But I can see that the power used at higher voltages was not lower than power used at lower voltages. So putting 4 cells in series is not better than 3 in series. S9WatsToVoltage.jpg

When I was testing I fount the most power (amps) was drawn when the motor starts. I had to find a pack that had the right configuration.

I also had a friend that had a 24v machine. I suggested he buy another 12v machine and use it for camping and as a backup at home. Much easier than figuring out all the battery/converter issues.

CPAP machines can be found quite cheaply on craigslist or facebook. I found my like new Dreamstation for a steal. of course you have to dump the heated hose and the humidifier when on battery so it makes more sense to have a separate machine.

[Cruiser51]

Great to see so many innovative ideas here!

Just curious, but where do you place your CPAP machine and battery when hammock camping? I am going to be trying to use mine this summer, but for the life of me, I cannot visualize how to keep it up off the ground and dry. I was thinking of maybe a Ridgeline Organizer or something, but just was not sure if the weight, with battery, would be too much. Thoughts or pics would be appreciated!

I have just swapped out to a GE hammock, but have been taking my machine in for about 7 years now ..... I started out using the ridgeline, but that is a bit of a pita to get all organized, it works, just not well enough for me. What I have decided might be a better alternative, is to use some of the wasted space at the head of the hammock. When I made my hammock, I put a gear tie on the inside of each end .... I intend to make a small gear holder, for my battery and unit, to just rest at the head of the hammock ... the space looks about perfect for purpose and doesn't require any hanging. The bonus is the tubing will be pretty much in the right place.

So I will just take the gear holder, attach it to the hammock end and let the battery and unit lay on the very end of the hammock .... it's out of the way, no hanging stuff to bang into your head, no wires and tubing all over the ridgeline .... just a neat little package tucked away on an unused section of the hammock.

If your hammock doesn't already have a gear attachment on the inside, it's pretty simple to put a loop onto the end loop and feed that through to the inside for the same effect.

Brian

[billbillw]

Hi folks, I'm just on the cusp of getting into hammock camping. I haven't even purchased a hammock yet, but I am a CPAP user and I'm trying to envision how I will make it work. I've been tent camping for some time with a 12V-22AH AGM battery (~13lbs). It has worked great for car/tent camping for 3-4 nights, but I'm not sure how I will get it to work with a hammock. I was thinking of having it hang from the tree straps/carabiners in some type of sling or dry bag and then running the wire in through the bug net. I could sling the CPAP from an inside fixed ridgeline, but I don't think I would like a 13lb battery hanging inside the hammock. Has anyone used such a heavy battery inside the hammock? I am also exploring the possibility of getting an oral appliance to simplify things, especially when backpacking. For now, I mostly camp with my son's scout troop in car camping situations, but as he gets older and does more backpacking, the heavy battery (and pack size of the CPAP) will be prohibitive.

[BigE94]

Hi folks, I'm just on the cusp of getting into hammock camping. I haven't even purchased a hammock yet, but I am a CPAP user and I'm trying to envision how I will make it work. I've been tent camping for some time with a 12V-22AH AGM battery (~13lbs). It has worked great for car/tent camping for 3-4 nights, but I'm not sure how I will get it to work with a hammock. I was thinking of having it hang from the tree straps/carabiners in some type of sling or dry bag and then running the wire in through the bug net. I could sling the CPAP from an inside fixed ridgeline, but I don't think I would like a 13lb battery hanging inside the hammock. Has anyone used such a heavy battery inside the hammock? I am also exploring the possibility of getting an oral appliance to simplify things, especially when backpacking. For now, I mostly camp with my son's scout troop in car camping situations, but as he gets older and does more backpacking, the heavy battery (and pack size of the CPAP) will be prohibitive.

Check out my first post in the thread. No need for 13lb batteries anymore. I now have a Chameleon with a sidecar and all of my CPAP gear goes in the sidecar out of the way but still in reach. Works a treat.

[billbillw]

Check out my first post in the thread. No need for 13lb batteries anymore. I now have a Chameleon with a sidecar and all of my CPAP gear goes in the sidecar out of the way but still in reach. Works a treat.

Well, seeing how I am probably not going to spend any money to get a lighter battery, then yes, there is a need. On a budget here. I don't spend enough nights out in the woods to justify spending $200+ on a LiPo battery (need enough for at least 3 nights). The AOMASO one you linked is apparently no longer available. I was curious and looked around. Can't find an think for that battery anymore.

Overally, I'm just looking at converting to a hammock for cooler summertime camping and less back pain. Not looking to totally re-invest.

[illogicallyovercome]

Have you thought of placing your large battery just under the head end of the hammock to see if your CPAP power cord can reach with it just sitting on the ground? For a longer trip, I'll be using a similar battery (car camping and not backpacking) to give me enough power to get through a week in the woods. I have not set up my hammock yet in the backyard to see if having my CPAP a the head of my hammock, with the large battery sitting beneath will work for me. I'll be playing with this setup this coming weekend to get everything ready... I'll also be treating my gear with permethrin to help keep the bugs at bay too, but that is for another thread...

[BigE94]

Well, seeing how I am probably not going to spend any money to get a lighter battery, then yes, there is a need. On a budget here. I don't spend enough nights out in the woods to justify spending $200+ on a LiPo battery (need enough for at least 3 nights). The AOMASO one you linked is apparently no longer available. I was curious and looked around. Can't find an think for that battery anymore.

Overally, I'm just looking at converting to a hammock for cooler summertime camping and less back pain. Not looking to totally re-invest.

Got it. Looks like batteries have gone up in price too. Just put the battery on the ground and run the cables to the ridge line. I used to have my CPAP in a RL bag with the hose running down and it worked great.

[JTaylor]

Thanks for all the info everyone! I have a friend that needs a CPAP nightly and cant camp as much as he likes due to the battery problem - I'll point him to this thread!