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Power outage
#21
RE: Power outage
Yep, running an inverter is very inefficient - probably going to lose 20-30% of power in the process.  Best to power the CPAP with 12 volt DC directly (no inversion loss).

Coffee
SuperSleeper
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INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.


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#22
RE: Power outage
(08-17-2018, 01:38 PM)OMyMyOHellYes Wrote: They beep when they go out.

They have small, tiny batteries.

They are really nothing more than a charger, tiny battery, and inverter in a box.  Inverters is bad when trying to run off a battery as it takes nice, clean 12 V DC, burns up power to convert that nice DC power into crappy AC power and step up the voltage, then run it to the CPAP's converter which turns it right back into 12 V DC power for the machine to use.  Kind of like driving to the house right across the street, but going around the block three times to get there.

Did I mention small batteries?

I modified mine by attaching a large external battery. Not something one would want to do unless they understand the tradeoffs, but it is a cheap, quick solution for my purposes.
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#23
RE: Power outage
For camping close to the car I have a 100AH Lead acid battery, Solar Panels with Charge Controller & Resmed DC Adapter.


This setup ran great for my last week away allowing me to charge my phone and use an Aircurve ST for a 6n night break with charge to spare (I don’t use a Humdifier). This is what I will use if there are any extended power outages. My power is generally stable, so no need of a permanent installation at home.
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#24
RE: Power outage
(08-17-2018, 07:31 AM)OMyMyOHellYes Wrote: NOT AN ENDORSEMENT OR RECOMMENDATION OR INSTRUCTIONS - just sharing what I have and how I put it together



If a picture is worth a thousand words ....  Substitute CPAP for the radio transmitter ......

This system is basically a 12 V setup using stuff normally targeted towards ham radio operators.  it consists of:

*  35-40 AH 12 V Sealed Lead Acid (SLA) or Absorbed Glass Mat (AGM) battery ~$70
*  West Mountain Super PWRgate  PG40S combination smart charger (like Battery Tender) and cutover switch ~ $135
*  Small 12 V power supply (I have a 12 am Astron switching power supply - SS-12) ~ $95
*  Wiring and connectors - These parts primarily use Anderson PowerPole connectors - can get them premade from West Mountain or Powerwerx or make them up if handy and and have, or are willing to get, a good PowerPole crimper
*  DC converter cord for CPAP
*  Cigar lighter socket cord to hook up the PWRgate to the CPAP DC cord/converter (if Resmed) - I cut off the cigar lighter part of the DC cord/converter and wired it direct to a PowerPole connector.
*  Appropriate fusing in the cord from the battery to the SuperPWRgate

Yes, it's pricey.  But even with the humidifier on I can safely get probably three nights on it.  Without heat humidifier, it can go a little over 8 nights (IIRC for the current draw studies I did on several machines)  If you remember JustMongo (former big honcho on this forum and electrical engineer by trade), he referenced the system as one of the most elegant (I think that was his word) that he had come across for this kind of application.

I will come back and edit as time allows.  Got to go earn green money ....

Being a ham I’ve seen that setup before. If you got the cash and can get everything that is a nice system. Same setup used on a lot of the repeaters.
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#25
RE: Power outage
Same setup I have duplicated in my shack.  Except bigger power supply and bigger cables feeding the SuperPWRgate from both battery and 35 amp powersupply and from the powergate to the Rigrunner. I think I used 10 GA wire....
There.  I said it.

OMMOHY
Contrarian in Residence  
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#26
RE: Power outage
(08-16-2018, 09:16 PM)sheepless Wrote: good to know.  here's a dumb question: apparently it's okay to plug the ac to dc transformer (that I presume the cpap 'brick' is) into a dc source (the ups)?   another: I guess it depends on the ups specs but even if it'll last longer than for a pc, is it enough power to get through a night? 2 nights?  how does one do the math?  gonna have to learn up on this...

Well, first refer back up in this thread re: using consumer PC UPS for my opinion.....

Question Numero Uno:  Yes, you can plug the AC-DC converter into the AC output of the inverter/UPS.  The inverter bumps up the voltage from 12 V to 120 V and turns it into AC current - usually a stepped approximation of a sine wave - more expensive units will put out an actual sine wave form.  Your AC-DC converter thinks it is plugged into an AC outlet at this point.  In spite of what you have heard, the stepped wave form is perfectly fine.  But be aware, the battery is burning current to do all of this and that's why folks urge not using inverters because of this inefficiency.

Question Numero Doso:  Most commercial UPS systems designed for PC use may not likely get you through two nights.  Or one night.  (I have seen some bigger UPS systems (1300 w rated units) opened up and they use 7 AH batteries or 9 AH (AH = amp hours)

Question Numero Treso:  Find out what the current draw is on your CPAP machine at your given settings.  Resmed has a battery guide that gives estimates of current draw in different configurations at different pressures.  You should be able to find one close to what you have.  It shows running both through the inverter and straight off the battery through their DC-DC converter (12 to 24 V step up - not really any apprciable loss in the DC-DC step up).  You will see that the machines lose a lot of reserve when going through the inverter though.  I tested current draw myself on several CPAPS over several nights each and found that their numbers were greatly on the conservative side.....  But if you find that the book says your unit draws 1.5 amps (that's hig, but in the realm of reasonable depending on how you run heated humidification) then you would divide the stated AH capacity of your intended battery by the current draw (say a 10 AH battery) .... divide 10 by 1.5 - that would give approx 6.67 hours of power.  But that is at the best condition on the first day that battery came out of the factory fully charged and under prime conditions.....  For safety sake figure 2/3 of that.....  so you should be able to get almost 4.5 hours safely.  The Resmed book is calibrated to show this 50% "emergency reserve" so you don't need to do the second step if you use it.....
There.  I said it.

OMMOHY
Contrarian in Residence  
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#27
RE: Power outage
thanks ohmymy. good scoop. and this entire thread had been very informative.
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#28
RE: Power outage
(08-17-2018, 01:38 PM)OMyMyOHellYes Wrote: They beep when they go out.

They have small, tiny batteries.

They are really nothing more than a charger, tiny battery, and inverter in a box.  Inverters is bad when trying to run off a battery as it takes nice, clean 12 V DC, burns up power to convert that nice DC power into crappy AC power and step up the voltage, then run it to the CPAP's converter which turns it right back into 12 V DC power for the machine to use.  Kind of like driving to the house right across the street, but going around the block three times to get there.

Did I mention small batteries?

It all depends on what you buy.

Mine has 2 x 20 Ah batteries, and is rated at 1500 Watts CAPACITY which is what it can supply at max load.
My unit has the option of 7.5, 10, 14.5, 20, 40 and 60 Ah sealed batteries depending on what run time you want.
If I wanted to go wet lead acid, i could go to 120 Ah, but I'd rather have AGM or SLA batteries inside the house for safety. Anybody wanting to use wet batteries with all the acid fumes and hydrogen they produce can do so at their own risk.
Mines a pure sinewave, listed as 92% which isn't too bad for the peace of mind that it provides. Its not a $75 modified square wave home pc user type unit and is fully online, so even when running on mains its rectifying, and then inverting to supply the output. This means no changeover time if theres a power outage, and continuous filtering. Spikes are not an issue as the output is supplied from the batteries all the time. Power fail beeper is disabled by a switch setting when programming.

So, while the standard home user units might have the failings that you describe, there are units out there that are a lot better and more suitable. All the CPAP "backup" units are just a UPS with a bigger battery capacity and a bigger charger to handle the battery fitted.

I therefore agree to disagree with your comments Bigwink
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#29
RE: Power outage
Thank you for the information about your UPS. matthewB. I wasn't aware that such large and adaptable UPS units were available. I'm curious as to what make and model it is, and how much it cost. (No links, of course). It sounds like a unit one might find in a medium size office, rather than a home office.
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#30
RE: Power outage
Thanks to all who've posted so far. Enjoying reading this. All good info for the learning experience about UPS, general and specific backup possibilities, etc. Coffee
INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEBSITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
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