How to run a ResMed AirMini on a USB power bank

[gork]

Hello all, I am new to CPAPTalk here, but wanted to share an interesting project that I have recently completed.

I built a cable to power my ResMed Air Mini from a USB power bank. The solution works great and is approximately 80% less expensive than purpose built solutions out there such as the very expensive Medistrom pack. I will give the requisite warning that you probably shouldn't go down this road if your sleep therapy is a life-and-death matter, but for me it is a thing that stops my snoring and helps me (and my wife) get a better night's sleep. And I'll be darned if I'm gonna pay 400 bucks just so I won't saw logs on the airplane!

So here we go. You need:

1) A battery bank supporting USB C with PD (Power delivery) that can supply 20V up to 30W or more. I use the Anker PowerCore+ 26800 PD which was well recommended and was on sale when I bought it. There are a variety of brands at this capacity ranging from about $60-120. 26800mAh works out to roughly 100Wh which is the TSA limit for a battery pack taken on an airplane.

2) A 20V USB PD Trigger cable. This device negotiates with a USB supply to tell it what voltage to output and then passes that through. This one https://www.amazon.com/dp/B07G1V1MXP is pre-set for 20V and works great out of the box.

3) A switching boost converter capable of 1A sustained load. A good choice is the XL6009 which is a 4A capable device but stays cool at the current levels requires for the AirMini. Here is one supplier: https://amazon.com/dp/B00LP2LZ4M/

4) A cable to plug into the AirMini. The thing uses a proprietary connector and for the life of me I searched for a compatible part but came up short. I haven't found a less expensive source than the $29 replacement cable for the aforementioned Medistrom Pilot-24. https://www.respshop.com/cpap-supplies/ ... -1218.html

The construction is pretty simple, cut the DC barrel jacks off of the USB trigger cable and the AirMini adapter cable, then solder them to the input and output of the XL6009 boost converter respectively, red to positive, black to negative. Check the output with a voltmeter and adjust the screw on the regulator until the output reads 24V. You can put a piece of heat shrink around the module to protect it or if you know someone with a 3d printer there are little cases for it on Thingiverse that can be made up easily.

I have monitored the power consumption through a USB power meter. With a good seal the unit draws a fairly nominal amount of power. I set my machine for 10 cm H2O static with now EPR just to get a nominal consumption number. The unit consumes approximately 200mW during exhale and approximately 15W when inhaling quickly. Over a 10 minute test I measured approximately 150mAh of power consumed, making the consumption approximately 1000mAh per hour. This means that for me the power bank could be expected to run the machine for over 24 hours. I probably wouldn't push it that hard, but I have run it overnight a few times no problem with my phone also plugged in.

All in all I think it's a pretty nice solution. I would be interested to know everyone's thoughts.

[remstarcpap]

Any ideas of how I would modify this setup to run an HDM Z1 cpap? It uses a power supply that yields 15 volts, although I think it will run on 12 volts too.

[CPAPSteve]

Hello all, I am new to CPAPTalk here, but wanted to share an interesting project that I have recently completed.

I built a cable to power my ResMed Air Mini from a USB power bank. The solution works great and is approximately 80% less expensive than purpose built solutions out there such as the very expensive Medistrom pack. I will give the requisite warning that you probably shouldn't go down this road if your sleep therapy is a life-and-death matter, but for me it is a thing that stops my snoring and helps me (and my wife) get a better night's sleep. And I'll be darned if I'm gonna pay 400 bucks just so I won't saw logs on the airplane!

So here we go. You need:

1) A battery bank supporting USB C with PD (Power delivery) that can supply 20V up to 30W or more. I use the Anker PowerCore+ 26800 PD which was well recommended and was on sale when I bought it. There are a variety of brands at this capacity ranging from about $60-120. 26800mAh works out to roughly 100Wh which is the TSA limit for a battery pack taken on an airplane.

2) A 20V USB PD Trigger cable. This device negotiates with a USB supply to tell it what voltage to output and then passes that through. This one https://www.amazon.com/dp/B07G1V1MXP is pre-set for 20V and works great out of the box.

3) A switching boost converter capable of 1A sustained load. A good choice is the XL6009 which is a 4A capable device but stays cool at the current levels requires for the AirMini. Here is one supplier: https://amazon.com/dp/B00LP2LZ4M/

4) A cable to plug into the AirMini. The thing uses a proprietary connector and for the life of me I searched for a compatible part but came up short. I haven't found a less expensive source than the $29 replacement cable for the aforementioned Medistrom Pilot-24. https://www.respshop.com/cpap-supplies/ ... -1218.html

The construction is pretty simple, cut the DC barrel jacks off of the USB trigger cable and the AirMini adapter cable, then solder them to the input and output of the XL6009 boost converter respectively, red to positive, black to negative. Check the output with a voltmeter and adjust the screw on the regulator until the output reads 24V. You can put a piece of heat shrink around the module to protect it or if you know someone with a 3d printer there are little cases for it on Thingiverse that can be made up easily.

I have monitored the power consumption through a USB power meter. With a good seal the unit draws a fairly nominal amount of power. I set my machine for 10 cm H2O static with now EPR just to get a nominal consumption number. The unit consumes approximately 200mW during exhale and approximately 15W when inhaling quickly. Over a 10 minute test I measured approximately 150mAh of power consumed, making the consumption approximately 1000mAh per hour. This means that for me the power bank could be expected to run the machine for over 24 hours. I probably wouldn't push it that hard, but I have run it overnight a few times no problem with my phone also plugged in.

All in all I think it's a pretty nice solution. I would be interested to know everyone's thoughts.

Omg! Exactly what I wanted to build. Thank you for writing this up. Super handy.

[remstarcpap]

Can you take some pictures of your rig? That would be helpful.

Also, in reading the reviews of the boost module, some people say if the input voltage drops below 5v, the output will spike over 50V, which could fry a CPAP. Is this a concern, or does the PD unit always stay well above 5v?

It sounds like you take the 20Volts from the PD and run it into the boost unit, to get 24V. Is there a way to get 12V for a Respironics machine, or 15V for my HDM Z1?

Thanks for your help.

[psteckler]

The suggested trigger cable is no longer available on Amazon. Would this one do:

https://www.amazon.com/USB-C-1-7mm-Emul ... B07PDWF4XR

You'd need a USB C male to USB C male to connect to it to the power bank. Also, the
input is spec'd at 65W or 87W, would that be an issue?

[remstarcpap]

The suggested trigger cable is no longer available on Amazon. Would this one do:

https://www.amazon.com/USB-C-1-7mm-Emul ... B07PDWF4XR

You'd need a USB C male to USB C male to connect to it to the power bank. Also, the
input is spec'd at 65W or 87W, would that be an issue?

Gork would know better than me, but since he never answers questions, I see it outputs 20V, and you need 24V, so the boost unit would still be needed. Not sure about the input issue...maybe one of our more engineering folks can answer that.

Gork, where are you?

[zonker]

Gork, where are you?

gork hasn't been on here since 1/27/19 unless he's come in on stealth mode.

[remstarcpap]

I know, I want him to come back on, since he clearly has good electrical engineering chops!

Come back to us Gork!!!

[zonker]

I know, I want him to come back on, since he clearly has good electrical engineering chops!

Come back to us Gork!!!

SHOUT LOUDER!!!!

[chartle]

If this setup puts out 20 volts and you need 12 volts you need a buck converter the opposite of a boost converter.

Something like this but I've never really played with them.

https://www.amazon.com/DZS-Elec-Adjusta ... pons&psc=1

Also if there is a cable to get it to to max output 20 volts there should be one to give you 12 volts since this is a common voltage for certain devices. But again I've only dabbled a little bit in this area.

I do know there are battery packs that can output 12 volts with just a switch but not sure if it can give you enough power aka amps.

ETA: Something like this can output 12 volts at 2.5 amps which is 30 watts. It even says 12 volts for CPAPS. But you would still have to cobble up a cable.

https://www.amazon.com/POWEROAK-Externa ... pons&psc=1

[psteckler]

I've ordered the parts to build a similar rig.

One modification I'm thinking of is to put a jack in an enclosure containing the boost board, rather than soldering the
cable that connects to the AirMini. Anyone know the details of the DC plug on the Medistrom cable?

[sarkanik]

5,5mm outer diameter x 2,5mm inner diameter. I am trying to build something similar.

[billbolton]

5,5mm outer diameter x 2,5mm inner diameter. I am trying to build something similar.

FWIW, a couple of generations of Lenovo Thinkpads used the same connector. Its a three pole connector - pin, inner ring, outer ring.

[psteckler]

The trigger cable I ordered ends in a 4.0 x 1.7mm male connector. That's different than the Resmed
connector, meaning it will be impossible for me to mix them up, if I have a jack for each in the box
containing the boost module.

The trigger cable should arrive by this weekend, so I'll know soon if it will work with the powerbank.

[psteckler]

Trigger cable arrived. On my first try to measure the output voltage, I was seeing 0 volts. My fear was that the Anker powerbank didn't have enough power to make the trigger cable work, or maybe the multimeter, also new, was bad. I tested the multimeter with a AA battery, and it seemed to be OK.

It wasn't clear that the multimeter probe was making contact with the metal inside the cable's DC output jack. So I took a short piece of wire, pushed it into the plug barrel, and used the meter's alligator-clip cable to connect to that.

Voila, I saw 19.9 volts DC.

So now I'm ready to build a box that contains the boost module, and connects to the trigger cable and the Medistrom/Resmed cable.