Choosing a Battery

[vinetpain]

I am on this cpap talk site primarily to find a reliable cpap that will run on a 12v deep cycle battery, and draw only enough to run for perhaps 5 nights use. I really enjoyed your post re battery differences, purposes et al, and it aligns with what I've learned regarding AGM btrys and Lion types.
My Question: Do you have recommendations, or can you direct me to a site wherein the manufacturer clearly states what their product's Amp hr draw is? Perhaps I need to know more, but right now, at least finding out what some relatively small (backpackable/kayakable) cpap draws will surely help me toward my solution.

Thanks

[khauser]

I understand what you're looking for but the fact is the best you'll get is estimates because a cpap machine draws different current depending on pressure setting and others.
5 days is only possible without humidification. The humidifier adds, in my experience, 2 or 3 times the amperage requirements.

The Respironics travel battery is a 90 Wh battery. According to them at a pressure of 10cm or less without heated tube or humidifier it'll last 14 hours.

This is a12v, 35 Ah battery. That's 420Wh, or almost 5 times.

Maybe that gives you some thinking points...

[migraine-]

I've read the opening guide, but I'm still struggling to work out exactly what I need to buy.

All I want is a battery I can rely on if the power goes out, since I have transitional apneas and NEED my CPAP to be able to fall asleep.

I'm in the UK so if anyone would be kind enough to link what I need to buy on UK websites that'd be greatly appreciated.

[mrCanoehead]

This is a12v, 35 Ah battery. That's 420Wh, or almost 5 times.

Maybe that gives you some thinking points...

The Medistrom 24 V unit seems to be around 4 A-h. As far as I can tell, the Duracell battery you posted could run my Airsense 10 for a week even with the humidifier on, seems oversized. It would not be convenient for travel.

Has any clever hacker ever tried using a DeWalt 20 V tool battery with a DC-DC boost converter to get it up to 24 V?

Does anyone know the pinout of the Airsense 10 DC input jack, and how to fool it into thinking it's connected to the proprietary power supply?

[khauser]

The Medistrom 24 V unit seems to be around 4 A-h. As far as I can tell, the Duracell battery you posted could run my Airsense 10 for a week even with the humidifier on, seems oversized. It would not be convenient for travel.

Has any clever hacker ever tried using a DeWalt 20 V tool battery with a DC-DC boost converter to get it up to 24 V?

Does anyone know the pinout of the Airsense 10 DC input jack, and how to fool it into thinking it's connected to the proprietary power supply?

Wiring a boost converter would be simple enough, but as you suggest, the connector has more than 2 pins. The outer shell and the inner barrel carry the 24v (negative on the outside). I measured the center pin at 3.3V referenced to the ground (outer shell). Another person (I found it here) shows that it can be done with a 3.3V signal that is connected via a 2.7K resister to ground. That is the 'signal' that the cpap needs to think it can run.

YOU ARE RISKING YOUR MACHINE AND DEFINITELY YOUR WARRANTY. Yes, their power converter is over-priced somewhat (compared to Respironics, which actually does nothing but filtering, it's reasonable) ... but you could also call it cheap insurance.

That signal might also be a clue to the cpap when some other condition, like undervoltage, is occurring. It is also key to whether the humidifier is powered. Providing our own trick signal defeats some of that intended purpose (all of it??)

There's no way to be very sure without reversing the entire power supply.

A DeWalt battery isn't 24V, right? It's 18. 18*4 = 72Wh

24*4 = 96Wh. Just under the 100Wh limit for taking it on a plane.

The Medistorm is designed to be used without humidifer. Depending on pressure needs it'll probably last several days. Turn the humidifier on and it'll probably be a day or less.

The DeWalt (or other) battery would be less.

If it were just batteries you cared about you could look at some of the 40V batteries that cordless snow blowers and lawn mowers used.

Whatever battery you choose, understand that it has some number of charge cycles before it won't be useful, and its capacity will decline over that time. Then you get to pay for the battery again. By that time, the expense of the adapter won't seem so much of an issue...

[mrCanoehead]

Thanks for the pinout electrical details.

YOU ARE RISKING YOUR MACHINE AND DEFINITELY YOUR WARRANTY.

Understood.

A DeWalt battery isn't 24V, right? It's 18. 18*4 = 72Wh

No. 20 V, 4 A-h. Would give similar capacity to the Medistrom.

https://www.dewalt.com/products/accesso ... ery/dcb240

They have another model with more capacity, but I want the smallest weight/form factor that will do the job. If it could be in my aircraft carryon, that would be fantastic.

I was going on a camping trip and asked my wife to buy a battery supply for my Airsense 10. She came back with a Medistrom 24 V battery and a receipt for $500. I don't think it should cost more than $100.

[mrCanoehead]

Duplicate post. Sorry for my double tap.

[khauser]

No. 20 V, 4 A-h. Would give similar capacity to the Medistrom.

https://www.dewalt.com/products/accesso ... ery/dcb240

They have another model with more capacity, but I want the smallest weight/form factor that will do the job. If it could be in my aircraft carryon, that would be fantastic.

I was going on a camping trip and asked my wife to buy a battery supply for my Airsense 10. She came back with a Medistrom 24 V battery and a receipt for $500. I don't think it should cost more than $100.

That's an 18V battery with 2V of marketing added to it:

Capture.PNG

[mrCanoehead]

Ha! Thanks for pointing that out!

I am going to try connecting the Resmed converter to it.https://www.amazon.ca/gp/product/B0721T ... UTF8&psc=1

I'm hoping the resmed will boost it from 18 to 24, and take care of any interface/protection issues.

[khauser]

That will work, but not sure how long.

Let us know!

[mrCanoehead]

I fought two levels of ResMed tech support and eventually spoke to someone knowledgeable:

The 90 Watt DC-DC converter at this link has a dual Voltage input range:

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

The low range is 10.5 - 13.5 V.
The high range is 21 - 27 V.

So as far as what they are saying, you can't connect an 18 V battery to it.

But this one might work:

https://www.homedepot.com/p/Milwaukee-M ... /300069523

[Dog Slobber]

But this one might work:

https://www.homedepot.com/p/Milwaukee-M ... /300069523

6Ah

If you turn off the humidifier, turn off the heated hose, go into airplane mode and lower the pressure, you *might* make it halfway through the night.

[mrCanoehead]

If you turn off the humidifier, turn off the heated hose, go into airplane mode and lower the pressure, you *might* make it halfway through the night.

I measured the draw of my Airsense 10 at the pressure I use, it is 1.4 A. Two of those batteries in parallel should do the job. The ResMed table sizes the battery at 150% of nominal though.

I will have to look up what "airplane mode" is. I've never heard of it.

[mrCanoehead]

Just wondered if anyone has tried the AntiGravity Batteries PS-45?

https://www.youtube.com/watch?v=oM0GPV2r4Vg

That one would run an Airsense 10 including the humidifier and heated hose all night, at least at my pressure.

I can charge it with my 100 W solar panel when I'm up north.

I need around 19 A-h (no humidifier nor heated hose) or 46 A-h (humidifier and heated hose).

I get nosebleeds if I don't run the humidifier.

[Dog Slobber]

Just wondered if anyone has tried the AntiGravity Batteries PS-45?

https://www.youtube.com/watch?v=oM0GPV2r4Vg

That one would run an Airsense 10 including the humidifier and heated hose all night, at least at my pressure.

I can charge it with my 100 W solar panel when I'm up north.

I need around 19 A-h (no humidifier nor heated hose) or 46 A-h (humidifier and heated hose).

I get nosebleeds if I don't run the humidifier.

There's not a chance that will run your AS 10 (with humidifier and heated hose) all night.

You've estimated your nightly requirements to be 19 Ah without Humidifier and H.H. and 46 Ah with.

That power station's capacity is 13.8 Ah