Re: How to run a ResMed AirMini on a USB power bank
Posted: Fri May 07, 2021 1:29 am
First I want to thank everyone in this thread for all their contributions to this topic. I was trying to find a way to power my ResMed AirSense via battery for camping trips without having to spend ~$300 for a clunky single purpose solution. Thanks to you guys I now have an AirMini that will make it so much easier to use my CPAP for these camping trips and when I start traveling for business again soon. I got to put the system through it's paces at a campout this last weekend and was real happy how everything worked out.
Second I want to rundown what I ended up setting up for running the AirMini off a battery. There are some different choices I made and I'll explain those, but I also wanted to offer all the updated links in one place as it was a bit difficult to piece it all together from the 4 pages of the thread. Here is the rundown with explanations to follow:
-AirMini CPAP Machine with AirFit F20 Mask Setup Kit: https://www.cpap.com/productpage/resmed ... ap-machine
-AirMini F20 HumidX Cartridges: https://www.cpap.com/productpage/resmed ... idx-3-pack
-AirMini Output Power Cable: https://cpapsupplies.com/bps-airmini-output-cable-only
-Weathertight 24 VDC Boost Regulator: https://www.amazon.com/Converter-Regula ... B01EFUHFW6
-USB C PD to 20 VDC Cable: The one I bought that is out of stock at the time of this writing: https://www.amazon.com/gp/product/B07XB ... UTF8&psc=1 and one that will likely work that is in stock: https://www.amazon.com/Cablecc-Charge-L ... RFQV&psc=1
-USB C PD 26800mAh Battery: https://www.amazon.com/Amazon-Basics-Ba ... JZXKY?th=1
-USB C PD Wall Charger: https://www.amazon.com/gp/product/B08KD ... UTF8&psc=1
So my goal was to simplify my travel kit so I didn't have to bring 4 wall chargers with me everywhere as well as allow for the option to run/charge any of my devices from a battery. So I simplified everything to run off of a USB C PD cable; it was easy to find those cables for my iPhone, headphones, laptop, and portable monitor. If you're not looking to switch over everything to PD and just looking for a solution to run your CPAP, the Amazon basics battery has the cables you need to connect it to a charger. If you don't already have a USB C PD Wall Charger I've been happy with the Aukey one linked above; I can charge my headphones in the USB-A, run my laptop off one of the USB-C, and still charge the battery to 100% in 3 hours.
For the CPAP I want to offer a clarification on the HumidX cartridge for the F20 masks. I ended up buying the F20 Mask Setup kit with HumidX on top of the mask setup kit that comes free with the CPAP, and I didn't need to do that. The HumidX cartridge for the F20 masks literally clips right into the inside of the mask, so you don't need a special hose interface like the nose pillows/mask. I could have just bought the 3 pack for $41 instead of the setup kit that only had 1 HumidX and the hose for $53. I also wanted to note that CPAP.com actually lists the HCPCS codes on the receipt so I could submit the purchase to insurance. I had a hard time getting that from my local equipment provider and they wouldn't submit anything to insurance without it. My insurance won't pay anything on it but it gets sent to my company's HRA who will pay it, so I'll get reimbursed without having to tap into my FlexSpend or savings.
As for the actual power cable to go from the battery/charger to the CPAP, I used the AirMini proprietary cable that psteckler linked. I didn't like the idea of buying from ebuy7 or other lesser know sites that were linked, so I found a USB C PD to 20v cable on Amazon. It's out of stock right now and I don't know if it will come back in stock for future readers, so I linked another one from the same company that should work. Really I don't think the cable has to be all that special and any USB C to 18-20 VDC cable should work, also referred to as laptop charge/power cables to help your Google Fu. And for the boost regulator to get the 20 VDC to 24 VDC that the AirMini requires, I wanted something that would hold up to the elements better since I am going to be using this for backpacking trips. I have a 3D printer and am pretty handy with CAD, but designing weather proof enclosures is finicky and I was happy to pay the extra $10 to get one that was already watertight without me having to futz around. I also didn't want to have to worry about the potentiometer getting bumped/jarred to a different voltage. One thing I did want to speak to in regards to that regulator, there are a bunch of one star reviews talking about how their unit "popped" or "exploded" that did worry me at first. But after digging through them I found in most cases people were connecting them directly to a 12 VDC car/boat battery which is a big no-no for something that provide hundreds of amps, they should have had it fused to 5 Amps to protect the regulator from the short they likely created. Also they were boosting from 12 VDC to 24 VDC, which will double the amp draw on the supply over the amp draw on the powered device. So a 5 Amp draw from the 24 VDC device would result in a 10 Amp draw on the 12 VDC battery which is at the 120 Watt limit on the difference in amperage. In our case we are only stepping from 20 VDC to 24 VDC with amperage limited devices, 0.83 Amp max draw from the 24 VDC CPAP which results in a 0.996 Amp draw on the 20 VDC supply; a fraction of the wattage the regulator is spec'd to handle. I've run it several times now for full nights on the CPAP and it has never gotten warm to the touch.
Now for the actual wiring, the USB C PD to 20v cable had a red and black wire once I removed the barrel plug. I used a digital multimeter (DMM) to confirm that the red was in fact the positive wire, a US wiring convention; but it may be different for other cables as the DC color coding is not a strict standard in the US. I joined that USB C PD cable to the matching red and black wires on the input side of the regulator. The AirMini cable had a brown and blue wire which is a CE standard (European) which is more strict so I am much more likely to trust that the brown wire is positive and the blue wire is negative. I did check with a DMM to verify (which is a pain on that AirMini plug). So I connected the yellow wire on the regulator to the brown wire on the AirMini cable, and then the black wire on the output side of the regulator to the blue wire on the AirMini cable. When I checked the full setup with my DMM I read 24.02 VDC on the output from both the battery and the wall charger so I was happy with that.
I wanted to try to avoid pulling out the soldering iron to make the splices, so I used some heat shrink & crimp butt connectors I had lying around. But I didn't like how bulky and inflexible the joints where which prevented it from coiling up nice for storage, so I ended up just soldering the splices and covering with heat shrink. If you don't have a soldering iron or don't care to solder, I'd recommend picking up some solder seal heat shrink butt connectors/splices and you can set the splice with a lighter if you don't have a heat gun. The only down side is that you typically have to buy them in kits so you get more than you need, but the are handy to have. Here is a link to an example: https://www.amazon.com/120PCS-Solder-Se ... r=8-3&th=1
Final results, I ran a few test nights at home before taking it out in the field. It ran just fine on the wall charger and the battery. One night would only drop one light on the battery indicator. I used to be at a fixed 18 cmH2O, but I lost some weight and they dropped it to the auto set range. If I had to guess I'm probably in the 12 cmH2O ballpark, so you're millage may vary if your above or below that. Finally took it on an overnight camping trip and I was able to use it for my CPAP and charge my iPhone 11 pro and my son's iPhone 6s from empty to full and still had more than 50% of the battery left. I think I could safely use one battery for a 2 night weekend camping trip without charging. I like to do a week long trip in the next year or so, for that I'll probably buy a second battery and might try getting this solar panel as well so I can charge the batteries during the day: https://www.amazon.com/dp/B08DCHF57B/ref=emc_b_5_t
Hopefully this helps.
Second I want to rundown what I ended up setting up for running the AirMini off a battery. There are some different choices I made and I'll explain those, but I also wanted to offer all the updated links in one place as it was a bit difficult to piece it all together from the 4 pages of the thread. Here is the rundown with explanations to follow:
-AirMini CPAP Machine with AirFit F20 Mask Setup Kit: https://www.cpap.com/productpage/resmed ... ap-machine
-AirMini F20 HumidX Cartridges: https://www.cpap.com/productpage/resmed ... idx-3-pack
-AirMini Output Power Cable: https://cpapsupplies.com/bps-airmini-output-cable-only
-Weathertight 24 VDC Boost Regulator: https://www.amazon.com/Converter-Regula ... B01EFUHFW6
-USB C PD to 20 VDC Cable: The one I bought that is out of stock at the time of this writing: https://www.amazon.com/gp/product/B07XB ... UTF8&psc=1 and one that will likely work that is in stock: https://www.amazon.com/Cablecc-Charge-L ... RFQV&psc=1
-USB C PD 26800mAh Battery: https://www.amazon.com/Amazon-Basics-Ba ... JZXKY?th=1
-USB C PD Wall Charger: https://www.amazon.com/gp/product/B08KD ... UTF8&psc=1
So my goal was to simplify my travel kit so I didn't have to bring 4 wall chargers with me everywhere as well as allow for the option to run/charge any of my devices from a battery. So I simplified everything to run off of a USB C PD cable; it was easy to find those cables for my iPhone, headphones, laptop, and portable monitor. If you're not looking to switch over everything to PD and just looking for a solution to run your CPAP, the Amazon basics battery has the cables you need to connect it to a charger. If you don't already have a USB C PD Wall Charger I've been happy with the Aukey one linked above; I can charge my headphones in the USB-A, run my laptop off one of the USB-C, and still charge the battery to 100% in 3 hours.
For the CPAP I want to offer a clarification on the HumidX cartridge for the F20 masks. I ended up buying the F20 Mask Setup kit with HumidX on top of the mask setup kit that comes free with the CPAP, and I didn't need to do that. The HumidX cartridge for the F20 masks literally clips right into the inside of the mask, so you don't need a special hose interface like the nose pillows/mask. I could have just bought the 3 pack for $41 instead of the setup kit that only had 1 HumidX and the hose for $53. I also wanted to note that CPAP.com actually lists the HCPCS codes on the receipt so I could submit the purchase to insurance. I had a hard time getting that from my local equipment provider and they wouldn't submit anything to insurance without it. My insurance won't pay anything on it but it gets sent to my company's HRA who will pay it, so I'll get reimbursed without having to tap into my FlexSpend or savings.
As for the actual power cable to go from the battery/charger to the CPAP, I used the AirMini proprietary cable that psteckler linked. I didn't like the idea of buying from ebuy7 or other lesser know sites that were linked, so I found a USB C PD to 20v cable on Amazon. It's out of stock right now and I don't know if it will come back in stock for future readers, so I linked another one from the same company that should work. Really I don't think the cable has to be all that special and any USB C to 18-20 VDC cable should work, also referred to as laptop charge/power cables to help your Google Fu. And for the boost regulator to get the 20 VDC to 24 VDC that the AirMini requires, I wanted something that would hold up to the elements better since I am going to be using this for backpacking trips. I have a 3D printer and am pretty handy with CAD, but designing weather proof enclosures is finicky and I was happy to pay the extra $10 to get one that was already watertight without me having to futz around. I also didn't want to have to worry about the potentiometer getting bumped/jarred to a different voltage. One thing I did want to speak to in regards to that regulator, there are a bunch of one star reviews talking about how their unit "popped" or "exploded" that did worry me at first. But after digging through them I found in most cases people were connecting them directly to a 12 VDC car/boat battery which is a big no-no for something that provide hundreds of amps, they should have had it fused to 5 Amps to protect the regulator from the short they likely created. Also they were boosting from 12 VDC to 24 VDC, which will double the amp draw on the supply over the amp draw on the powered device. So a 5 Amp draw from the 24 VDC device would result in a 10 Amp draw on the 12 VDC battery which is at the 120 Watt limit on the difference in amperage. In our case we are only stepping from 20 VDC to 24 VDC with amperage limited devices, 0.83 Amp max draw from the 24 VDC CPAP which results in a 0.996 Amp draw on the 20 VDC supply; a fraction of the wattage the regulator is spec'd to handle. I've run it several times now for full nights on the CPAP and it has never gotten warm to the touch.
Now for the actual wiring, the USB C PD to 20v cable had a red and black wire once I removed the barrel plug. I used a digital multimeter (DMM) to confirm that the red was in fact the positive wire, a US wiring convention; but it may be different for other cables as the DC color coding is not a strict standard in the US. I joined that USB C PD cable to the matching red and black wires on the input side of the regulator. The AirMini cable had a brown and blue wire which is a CE standard (European) which is more strict so I am much more likely to trust that the brown wire is positive and the blue wire is negative. I did check with a DMM to verify (which is a pain on that AirMini plug). So I connected the yellow wire on the regulator to the brown wire on the AirMini cable, and then the black wire on the output side of the regulator to the blue wire on the AirMini cable. When I checked the full setup with my DMM I read 24.02 VDC on the output from both the battery and the wall charger so I was happy with that.
I wanted to try to avoid pulling out the soldering iron to make the splices, so I used some heat shrink & crimp butt connectors I had lying around. But I didn't like how bulky and inflexible the joints where which prevented it from coiling up nice for storage, so I ended up just soldering the splices and covering with heat shrink. If you don't have a soldering iron or don't care to solder, I'd recommend picking up some solder seal heat shrink butt connectors/splices and you can set the splice with a lighter if you don't have a heat gun. The only down side is that you typically have to buy them in kits so you get more than you need, but the are handy to have. Here is a link to an example: https://www.amazon.com/120PCS-Solder-Se ... r=8-3&th=1
Final results, I ran a few test nights at home before taking it out in the field. It ran just fine on the wall charger and the battery. One night would only drop one light on the battery indicator. I used to be at a fixed 18 cmH2O, but I lost some weight and they dropped it to the auto set range. If I had to guess I'm probably in the 12 cmH2O ballpark, so you're millage may vary if your above or below that. Finally took it on an overnight camping trip and I was able to use it for my CPAP and charge my iPhone 11 pro and my son's iPhone 6s from empty to full and still had more than 50% of the battery left. I think I could safely use one battery for a 2 night weekend camping trip without charging. I like to do a week long trip in the next year or so, for that I'll probably buy a second battery and might try getting this solar panel as well so I can charge the batteries during the day: https://www.amazon.com/dp/B08DCHF57B/ref=emc_b_5_t
Hopefully this helps.
