Uninterruptible Power Supply for CPAP

[ProfessorSleep]

That's very kind of you, yardbird. But, 2 questions (1) where would I find that info? I've been all over the manufacturer's site and the specs and don't see that info. (2) In the absence of that info, could we assume a typical (if there is such a thing) draw of power, knowing that the HH will decrease that considerably, and overestimate the size of the UPS needed? Seriously, I'd rather have too much backup, so would gladly err on the side of being too large. I also understand the time provided by such a backup might be decreased. But 4 hours sleep is better than none, should it be that low. I'm thinking I should think big, along with thinking safety?

I also found a lot of (again, very technical) info at this site:

http://www.newtechpub.com/sleep/magazin ... wer01.html

There is mention in there of never running a HH from an inverter. I am assuming that is not an issue with a UPS since it is not the same as running straight off of DC current? Also, my humidifier is integrated, which might make a difference?

I can rebuild a motorcycle carburetor. Why is this electricity stuff so difficult? Maybe because I know that if I should goof with a carb. jet or something it won't shock someone to death or start a fire?

You guys are too kind!

[yardbird]

hmmm... you're right about heaters and inverters. Heaters are like .... well they are resistance. That what makes heat. Kinda like a controlled short.

Do the heaters for the humidifier plug into the CPAP or do they have their own power plug? They *could* have both. One for control and one for power. Is it painfully obvious I don't have one with a heated humidifier?

I'll see if I can find this on line too...

[ProfessorSleep]

the f&P unit, and I think the Resmed S8 that I might have access to, do not have a separate power supply. I am certain this is the case with the F&P. There's a sort of hot plate thing built in to the front of the unit, and the water chamber just slides on that. I *think* it can be turned off, I know it has settings 1-5 (not sure about no heat at all). Part of the problem, though, would be if I am not aware of the power going out, I would have either machine running with the HH (I live in WI - HH is essential, for me anyway) and the HH would be on when the unit switched to UPS. Any ideas?

[derek]

You can buy a 120 x 1.25 = 150 w unit if you wish, in fact most UPS's are rated much larger wattage than that, but I guarantee the cpap itself draws much, much less on average - otherwise it would get really, really hot to the touch.

It's not the heater itself in the humidifier that might be fried by an inverter - it's the electronics used to control the temperature of the water that are at risk.

[ProfessorSleep]

Thanks, Derek! (great avatar, by the way). So am I putting my unit at risk by using a UPS? If so, is there an alternate arrangement that will work safely, or is the best option to have a separate CPAP and humidifier with the cpap on the UPS and the humidifier not plugged into it? For example, I could get the S8 with an addon F&P 150 HH that would plug in separately. I could then plug the S8 into the UPS and the HH into the wall outlet. Power goes out, at least there is still cpap.

I believe the F&P HH data indicate that unit is compatible with an inverter. If so, it could be plugged into the UPS, right?

I'm content with the F&P234 cpap with integrated humidifier that I have. I'd like to hook that whole thing up to the UPS if I won't fry the HH. Any other options for that?
Thanks--

Beth

[yardbird]

Ok this sounds like a deal breaker. I'll paste it, but it's a bit technical. The short version of what I'm about to paste is:

DO NOT use a UPS on a CPAP with heated humidifier.


Will I have enough power to run a heated humidifier?

Heated humidifiers are not compatible with most types of inverters, and such use is likely to result in burning out the humidifier heating element.
WARNING: Do not use an inverter power source to run a heated humidifier.

Code: Select all

Technical explanation, adapted from information supplied by Shane Finn at ResMed: Humidfiers use a triac or thyristor to regulate the power by turning on partway through each mains cycle. The controller assumes the mains voltage is sinusoidal. However, inverters generally do not provide a true sinusoidal output, thus the controllers make wrong decisions and cause the humidfier to deliver full power continuously, and may burn out the heating element. Another, more intelligent type of controller is termed an integral cycle controller or burst controller, and would provide full power in short bursts. However, we know of no heated humidifier using this type of controller.

********* end of paste***********

So unless you have a battery backup approved by your machine's manufacturer for use with a heated humidifier, I STRONGLY suggest you don't do this yourself unless you want to burn out your heater.

[derek]

Yardbird.
Excellent statement! Electronic devices with semiconductors such as SCR's or thyristors in their power supplies are very susceptible to the modied-sine-wave that comes out of inexpensive inverters. The much more expensive "true-sine-wave" inverters are ok, however.

Thanks for the comment on Kaycee in the avatar. He's a 19 week old Cavalier King Charles Spaniel, (hence the name Kaycee) and a delight to have around. He's our second Cavalier, we lost our first one 18 months ago.

[ProfessorSleep]

OK, so a "true sine wave" thingy is ok? I'm guessing those are off the planet price-wise? What about the option of setting up the S8 on a UPS and a separate HH not plugged into the UPS? Then, if the power goes out, the UPS comes on and runs the CPAP only, while the HH would be unavailable for awhile. It's better than nothing, I guess. There must be some option for this!

Sorry to hear about your previous dog, Derek. Those KCs are great dogs. I've got an 8 month old golden retriever that keeps me running! This is my 4th golden - dogs are a great exercise program, in addition to being wonderful buddies.

Now, about that backup power supply..... what to do?

[derek]

Yep, thats what I effectively do - run the humidifier off regular ac and in a power-outage I simply lose the humidification, which for me is not a big deal.

I just did a quick google search on "pure sine wave inverter" and found 300 watt ones starting at around $120. While that should be adequate, be aware that a humidifier will draw way more current than the xpap and you really must have a large marine/RV deep-cycle battery to run your humidifier. The little (20 Ah) batteries in UPS's (or the PowerPack like I have) would last no time at all with a humidifier running.

I have no idea how good these inexpensive pure sine-wave inverters are.

[ProfessorSleep]

OK, so I've got a solution. I'll take the S8 Escape, plug it into a UPS, and get a separate HH to plug into the wall. I can do this! Yeah! I can plug things in! That will be my setup during thunderstorm and blizzard season (which, come to think of it, will cover much of the year!). So I'm ok with that. Anything else I should know? Any of the problems with blowing up the S8 that johnny talked about, or is that a moot point if I'm not running on a direct 12v connection?

I can't thank you all enough for the help. This has been worrying me for quite awhile. It will be great to have something set up for those certain outages. I like the UPS idea because of the brown out and surge protection also. Would that setup still be preferable to a Xantrex arrangement, such as you have, Derek? Anything else I should know?

With many thanks --
Beth

[derek]

Beth,
I looked at the Belkin and APC web sites. The specs are very confusing. As I said earlier, the importand thing is the battery size (in Ah), not the the wattage (or VA) rating. The APC site does give a breakdown of time vs power, but they only go down to 50w. All in all I concluded that they all use smallish batteries.

In the meantime I just did some experiments on running my Respironics Auto (in CPAP mode at 10cm) running off the Xantrex PowerPack 400 Plus. The question I was asking is whether it would be possible to run the APAP off the inverter, leaving the inverter on all day. The concern is that the battery charger is very small and rated at less that 800 mA (0.8 amp). Would the charger be able to keep up with the all-day current drain of the inverter on, and the APAP connected but turned off?

I measured the current in and out of the battery, and concluded that just having the inverter turned on, but with nothing connected drew 0.15 amp.
I plugged in the charger, with the battery almost with full charge.
1) With the inverter turned off the charging current was 0.36 amp.
2) With the inverter turned on, but nothing plugged in, the charging current dropped to 0.27 amp.
3) With the inverter turned on, and the APAP plugged in but not turned on, the charging current dropped to 0.04 amp.
4) With the inverter turned off, and the APAP plugged in to the 12v dc outlet but not turned on the charging current was 0.2 amp.
5) Then with the charger disconnected, and the inverter on with the APAP plugged in but not running, the current drain was 0.45 amp.

My conclusion is that the current drain from running the inverter all day with an xPAP connected (but not turned on) will probably prevent the charger from bringing the battery up to full charge each day.
If you want to use the PowerPack 400 with the inverter you should turn the inverter off during the day.

Here are my attempts to measure the current drawn by the system with CPAP at 10 cm and C-Flex set at 3. It's very difficult to guess because the current jumps around a lot:
With the charger connected, running on dc:
Inhale: 0.2 amp (discharging battery)
Exhale: -0.05 amp (charging battery)

With the charger connected, running from the inverter:
Inhale: 0.6 amp (discharge)
Exhale: 0.3 amp (discharge)

The conclusion is that on dc power, the charger is almost able to keep up meaning that the battery is in pretty good shape in the morning, but on ac through the inverter, the nightly load would take about 3.5 Ah out of the battery (8 hours times an average of 0.45 amps) which has to be replaced by the charger during the day. 16 hours at 0.04 amps is not nearly enough time to do that.

[ProfessorSleep]

Gee- I actually understood that! Thanks - very nice explanation. So, do you keep your power pack charged and at the ready to hook up if you need it (in which case it would stay plugged in all the time with no drain unless needed. Hopefully the charging mechanism switches to "float" when the battery pack is fully charged?) Then it goes into service during an outage?

Why would some battery packs not be compatible with some CPAPs? since the S8 without humidifier seems to be my only power outage option at this time, do you think the UPS or the Xantrex would be best? I'll just keep using my F&P and hook up the other flow generator if there is an outage.

More questions - along with more thanks!

[SickAndTired]

<snip>
The conclusion is that on dc power, the charger is almost able to keep up meaning that the battery is in pretty good shape in the morning, but on ac through the inverter, the nightly load would take about 3.5 Ah out of the battery (8 hours times an average of 0.45 amps) which has to be replaced by the charger during the day. 16 hours at 0.04 amps is not nearly enough time to do that.

Very nice analysis as usual Derek!

If the Xantrex XPower Powerpack 400 Plus runs this close to the 'edge' of keeping up with the requirements of a Respironics xPAP @ 10cm on DC power, do you think the XPower Powerpack 600HD would be able to keep up with one of the new Auto BiPAP machines at a possible 20cm? Or should I resign myself to getting one of the "big daddy" XPower Powerpack 1500 (would really like to avoid having to lug that monster around if possible)?

Based on the specs, since there's no real data yet, do you think the 600HD could keep up with the Auto BiPAP?

[derek]

S&T,
The 400 Plus has a charge indicator LED: when it's flashing the battery is charging, when solid on, the battery is fully charged. With the Auto the LED is always on, even first thing in the morning, which indicates to me that the charger is able to supply the current throughout the night.

There is no way that I can extrapolate my experience to the Auto Bi-Level machines because I have no idea how much current they draw on dc.

I took a look at the PowerPack 600HD specs. What you would get is a 28 Ah battery vs, 20 Ah, a charge rate of 1 amp vs. 0.8amp, and a downright ugly looking unit The extra battery capacity might be useful - it might give you an extra night in a blackout, and the slightly higher charging rate may also help. I think the PowerPack 1500 would be way overkill, and even uglier. It's 15 in tall (withouout the handle), so it proably won't fit under the bed.

[SickAndTired]

<snip>
I think the PowerPack 1500 would be way overkill, and even uglier. It's 15 in tall (withouout the handle), so it proably won't fit under the bed.

Not to mention that I think the 1500 refers to the weight instead of the capacity!