Homemade Resmed A10 camping battery

Hi folks, I'm new to the forum. I've been searching, both here and around the internet in general, and I haven't been able to answer a couple questions I have.

First one: what is the Voltage range of the ResMed A10? I've heard rumors that it will work as low as 12V, but all the official stuff I can find says 24V, and that's it. I know that most DC stuff can run on at least some range, but I don't really want to use my machine to test it out.

Second: does anyone know the type of barrel connector that fits the ResMed A10? For example, I have lots of 5.5mm x 2.1mm connectors.

The reason for these questions, is that I'm looking for alternative ways to power my cpap. I'm often away from electrical outlets for days at a time. And batteries that I've found for sale are way too expensive, and wouldn't last long enough anyway.

The inner pin is +3.3 volt
The inner cylinder is +24 volt
The outer cylinder is ground

Not sure of the size

rebelrider.mike wrote: ↑

Wed Aug 21, 2019 1:31 am

Hi folks, I'm new to the forum. I've been searching, both here and around the internet in general, and I haven't been able to answer a couple questions I have.

First one: what is the Voltage range of the ResMed A10? I've heard rumors that it will work as low as 12V, but all the official stuff I can find says 24V, and that's it. I know that most DC stuff can run on at least some range, but I don't really want to use my machine to test it out.

Second: does anyone know the type of barrel connector that fits the ResMed A10? For example, I have lots of 5.5mm x 2.1mm connectors.

The reason for these questions, is that I'm looking for alternative ways to power my cpap. I'm often away from electrical outlets for days at a time. And batteries that I've found for sale are way too expensive, and wouldn't last long enough anyway.

The best way to power your Resmed device is to purchase the Resmed DC adapter this is pricey at $70 but will work on 12 or 24 volts and will drive your machine without risk, if you want to go DIY then there are some details here somewhere

Thanks for the replies!

I did not realize the barrel connector had 3 conductors. Very good to know. I was talking to a fellow earlier who also suggested the 12/24V DC adapter to go between the CPAP and any other DC power source. His thinking was it's a boost/buck converter with maybe extra safety stuff. Looks like it also supplies two different Voltages. And also I wouldn't have to worry about what type of connector to get.

I think the adaptor will be my first step. Don't quite know how I'll power it yet, but this is a good start. Thanks!

The A10 uses much more power when using the humidifier and heated hose.
I have a solar cell system on folding stands that charges a battery for use in power outages here. I tested several days use from a single charge with humidifier off and no heated hose.
The solar panels are glass but on folding stands. The system could work if you have the transportation space in your situation.

rebelrider.mike wrote: ↑

Wed Aug 21, 2019 11:45 pm

Thanks for the replies!

I did not realize the barrel connector had 3 conductors. Very good to know. I was talking to a fellow earlier who also suggested the 12/24V DC adapter to go between the CPAP and any other DC power source. His thinking was it's a boost/buck converter with maybe extra safety stuff. Looks like it also supplies two different Voltages. And also I wouldn't have to worry about what type of connector to get.

I think the adaptor will be my first step. Don't quite know how I'll power it yet, but this is a good start. Thanks!

The Resmed dc converter is very efficient... I opened mine up, and it's very well built inside.

prodigyplace wrote: ↑

Thu Aug 22, 2019 3:27 am

The A10 uses much more power when using the humidifier and heated hose.

As do ALL cpaps.

Finally got to order the DC-DC converter. I plan to test it at different Voltage inputs to see how the 24V output behaves. I've also got a bucket full of rechargeable cells to test out and hopefully make a good battery. (I can explain that further if anyone is interested.)

In other news, I've finally got to talk to my Dr. about what to do when I'm out in the wilderness for several days. He says the best option is to get a portable cpap and battery. I could get an oral appliance, but that will cost a lot, and wouldn't be covered by my insurance. He's also reassured me that my apnea is not severe enough to worry about health effects after a week of backpacking with no machine. As long as I'm using it the rest of the time.

A search here has given me 20 threads about hiking/backpacking which I need to read through. And I have an inquiry out to my hiking forum friends to see what they do. So hopefully, I'm about to have a lot of learning in my near future!

I hope you reach an affordable, safe alternative to the over-priced OEM,
rather than a face-full of magic smoke!

I have a 65AH battery charged by a solar panel kit to use during power outages. I ran 2 or 3 days with no humidifier or heated hose when I tested the battery.

ResMed has a document to help you estimate the battery requirements.

https://www.resmed.com/us/dam/documents ... lo_eng.pdf

Not to worry, I'm a battery nerd, and none of my creations have ever let any smoke out. I put a lot f safety features into them, and all the cells are thoroughly tested before I'm willing to use them.

Since I'm still waiting for parts, I'm playing around with a diagram of how the parts should go together.


Depending on how the adapter behaves, I may get an external Voltage regulator. The adapter is supposed to convert from 12V and 24V systems to the 24V for the cpap. In vehicles, that would be between say, 11V-14v, or 22v-28V, depending on which system, so we'll see how well it works. Should get here next week.

I plan to have a 635Wh battery, which should give me around 32 hours of use. I've been sleeping at home and on a couple camping trips with the heater and humidifier off, and I haven't missed them.

This is all for the primitive camping, by the way. Between the hiking/backpacking threads here, and the responses I've gotten from my hiking forum, there aren't really any solutions that will work for me. Everything is either too heavy or prohibitively expensive. Or doesn't seem to work for most folks. So I'm going to focus on the camping battery here. Not giving up hiking, but I have the whole winter to think on it. And maybe even lose some weight.

The DC-DC adapter is here! Finally get to experiment a little.


here is the DIY adapter I made to test the output.


A simple loop for the outer ground ring. Inner ring is a wire wrapped around another wire and held in place with the insulated wire with tape around it to get the width right. That will contact the inner 24V ring. Finally, the center pin connects with a short insulated wire, where I've taken a few strands out to make room for the pin. That would be 3.3V.


With that in place, I made a temporary 3s battery to test the adapter's ability to boost Voltage and keep it at 24V under a lode. The battery connects to the adapter, which connects to a CV CC regulator, which connects to a 12V 21W light bulb.


With the battery at just under 11V, the output is at 24V without a load. Not pictured is the center pin at 3.2V.

Under a load of about 20W, the battery drops to around 9V, and yet the adapter's output remains at 24V, and 3.2v.


So the adapter is a good boost regulator and can go as low as 9V input, maybe even lower.


Next I put together a 7s battery to test the adapter's ability to reduce Voltage. Same setup as last time, but with the bigger battery.


With no load, the battery is about 26V, and the adapter still outputs 24V and 3.2V.


Again, under a 21W load, The battery drops in voltage, but is still above 24V. The adapter's output remains at 24V, and 3.2V.


So between this and another DIYer's experience with a fully charged 29.4V battery, I'm convinced that this adapter is also a buck/boost regulator. Which means I don't have to install one on the battery.

I just ordered a bunch of stuff to start building the permanent battery. In the meantime, I'm charging up a temporary 6s battery to actually run the cpap off it for a couple hours.

The temporary battery was a success! I took a 2hr nap with the cpap running off the battery through the adapter/regulator, and it worked great. The battery I used was a much smaller version of the battery I'm building for travel. Same Voltage but less capacity.

My BMS finally arrived from China! Still plugging away at testing cells though. So far, I've done around 70 or so, so I'm almost done. The best 66 will go in the battery.
I've realized I can't get a 4A fuse, so I'll make due with a 5A. Using the axial glass 0.5A fuses on each cell, that would allow the battery to deliver almost 11A before they start to blow. So a 5A main fuse will definitely pop before that. (I hope.)

I've been playing with an actual wiring diagram, to better imagine where all the parts will go. Here's what I've got so far:


I definitely wanted a Voltmeter to show the battery status, but I decided to spend a couple extra bucks (I know, unusual for me.) on a Wattmeter. This will show Volts, Amps, Watts, and Whrs, to give me a better idea as to how the battery actually performs vs my math estimates. Plus, it has a low Voltage alarm that can be set. The BMS should shut it down automatically if the Voltage gets too low, but I've never really trusted BMSs.

If I can fit them in the box, I'd like to have the option of taking a battery charge controller and the AC adapter, in case I come across electrical outlets in my travels. Once I get the box, I'll be able to do a mockup of all the parts and see what will fit, and what physical shape I'll make the battery.

Very cool.

Roger

I've got the very same buck converter sitting on my project table.

Thanks for the info.