Minimum DC Voltage to Operate CPAP?

[khw210]

Thanks. I use a DC power meter that records amps used over time along with a few other perimeters including voltage. But the question still remains - What is the minimum voltage required to run my machine?

[SuperSleeper]

But the question still remains - What is the minimum voltage required to run my machine?

I seriously doubt you'll get any firm answers from a Respironics source.  They might have a "recommended range" of acceptable voltages, but the "minimum voltage" to run any particular machine with varying pressures is going to be a changing number, if you have it set in auto-CPAP mode.

I suspect you'll have to rely on your own testing.  And even then, all you're going to get is "on this certain night, with this particular battery, my CPAP stopped working when this particular battery charge reached x volts".    It's doubtful that you can compare that information if you switch something, changing another variable like the battery type.

I think the more important question is-- at what voltage do I want to disconnect from the battery in order to preserve the life of the battery and protect my CPAP from potential damage?

I can't help but think that operating a CPAP motherboard with less-than-ideal voltages can't be a good thing.  That's the essence of what is called a "brown-out" when using grid electricity.  Computers and motherboards can be easily damaged by such voltage issues.  Perhaps Respironics has built-in protections or shut-off switches for when there's not sufficient voltage, but do you want to risk damaging a $500+ CPAP machine just to test a less-than-adequate battery setup, when you have no assurances that such protections exist on the machine?

So why not get a battery with sufficient amp hour rating to give you plenty of buffer, just in case?

My go-to for travel in campgrounds is a 12 volt deep cycle lead-acid system.  Cost = about $120.  The battery is about the size of an automobile battery and is rated at 105 amp hours.  I can fully charge it up to over 13+ volts and get by with nearly 4 full nights without a re-charge, and without the battery getting much below 12.3 volts, open-terminal with no load (not using heated humidifier).  Unless you're going back-packing on foot, or on a motorcycle with little space, there's no reason you can't fit a full-sized 12 volt deep cycle in your car is there?

[Jeff8356]

Phillips sells a "PAP Battery Kit" which is a small portable lithium ion battery/ups.  The specs for their battery are:

   

It doesn't say if it cuts off the power at 11 VDC, but it's probably a safe assumption that it's the minimum voltage.

The ResMed dc-dc converter specs say it cuts off voltage to the xPAP when the battery supply voltage drops to 10.5 VDC.

Either way, I would stick with the 11 VDC minimum.


But I agree with SuperSleeper.  Unless your backpacking/mountain climbing/etc. where size is an issue, my choice would be an AGM or Gel deep-cycle.

[SuperSleeper]

Phillips sells a "PAP Battery Kit" which is a small portable lithium ion battery/ups. 

Very nice setup, but at a cost of  over $400, a bit on the pricey side.      And they're only good for perhaps 1-2 nights before re-charge is necessary.

But heck, if money wasn't an issue, and I wanted one for off-grid camping, I'd get one in a heartbeat.  

[daddyoh]

I'm a newie
Yep, very interesting topic on Power Supplies to run CPAP machines, so glad I came across this Forum. 

@khw210 
clintber and other posters are right, the AMP meter records the current which passes through it at that moment in time.
It connect between the power source (bat) and the destination (Load).

You want at least a 40Ah battery to carry you over the night and to give you some reserve so you don't thrash the batt beyond it's recovery to 100%

[khw210]

Below is an email response to my question from Phillips Respironics!


************************************************************
I reached out to our BioMed support department.  They advise it will not operate below 10.8VDC.  If you have any additional questions, please feel free to call us at 800-345-6443, opt # opt 5.  We are available Monday thru Friday, 12pm to 5pm Eastern time.

Best Regards, 
Philips PCMS Patient Interaction Team
Sleep and Respiratory Care
PAR
 
Philips Respironics Pittsburgh, PA 15239
Tel: 800.345.6443
Email: pcms.support@philips.com
Team Hours: 12 PM- 5:00 PM EST

*************************************************************

10.8V is a bit lower than I expected. Much lower than i will allow my battery voltage to drop - if I can help it.

[SarcasticDave94]

I'm surprised you got a response as detailed as this, let alone that you got a response.

[Sleepster]

Now that you know the minimum voltage what will you do with that knowledge? You still need to test your battery under real life conditions to determine how long it will last. It's best to do this while at home rather than waiting until you go camping.

[RayBee]

Below is an email response to my question from Phillips Respironics!
They advise it will not operate below 10.8VDC.

Good info and welcome to hear their response and support of such a question.
Interesting though.  That's flirting in the and around the minimum recommended voltage of a 3S LiPo battery pack - depending on what your discharge practices are.  3.0 to 3.7 volts per cell.  Lower = less recharge cycles and less life out of a battery pack.

[khw210]

An update on my quest to learn the voltage tolerances of my Respironics System One Series 60 CPAP machine.
I have a new battery that i'd like to use to power my machine when "off the grid". It's a 4S LiPo battery that, at full charge, provides 16.8 volts. I know that's too high but wondered what the maximum voltage my machine can tolerate...  I again contacted Respironics Customer Service and they responded with:

From: Respironics Service <Respironics.service@philips.com>
Sent: Wednesday, August 12, 2020 9:08 AM
To: pcms.support (Functional Account) <pcms.support@philips.com>
Cc: Respironics Service <Respironics.service@philips.com>
Subject: RE: DC voltage tolerance? reply MJ
Hello,
               The device will not operate above 15.5 VDC and below 10.8VDC.
Regards,
Product Support

So, there you have it. When I choose to use the LiPo battery, I'll charge it to a value less than 15.5 volts and be good to go. Charging any Lithium battery to less than 100% is good for the battery anyway.