Power outage

[OMyMyOHellYes]

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 ....

[SarcasticDave94]

Thanks for the backup info. Looks like an easy enough DIY as far as I see it.

[Coffee Man]

Stay.

Away.

From.

Computer.

UPS.

Why? I have my APAP on a computer UPS and it has run just fine through several power outages.

[mesenteria]

If you want 'quick 'n easy'...hehe... ya gotsta pay.  I see the CDN price for the RESMED converter and/or battery for the AS10 series is as much as I paid for the Elite itself!

I'm beginning to think that, for a straight bedside backup, you'd want a marine/deep cycle battery, a good one ($200+), a suitable converter, and a 'smart' charger for the battery.  For a more portable setup, have the hosts at the far end provide the battery.

I haven't done a great deal of reading up on UPS's, but I did some internet sleuthing one night not long ago. I came to the conclusion that the ones that will get us through even a single night are quite costly all by themselves.  You still need a way to get it connected to the PAP device.

[matthewb]

Stay.

Away.

From.

Computer.

UPS.

Why? I have run my Bi-pap on a 1500W UPS for 5 years now, all i did was disable the mains power fail beeper so it didn't wake me. I have a lot of outages here (rural area) and it has worked fine.

[SuperSleeper]

I think the issue with off-the-shelf smaller consumer-grade UPS devices (designed for computers) is that the lead-acid battery in most of those UPS devices are woefully inadequate for continued CPAP use, especially if you have a heated humidifier. (these usually to not have enough amp-hours) The problem is that if you run a lead-acid battery (even a deep cycle one) too far down in charge, you'll damaging the battery and the lifespan of the battery will be greatly reduced.  The key is not to run a deep cycle battery down much below an 80% remaining charge before you recharge it - that will allow a normal battery lifespan.

I would challenge anyone who thinks that a standard UPS with a low amp-hour rating will be sufficient to power a CPAP for an entire night (8 hours) without damaging the battery.  Most consumer-grade UPS devices have 10 amp-hour batteries or less (much less, usually).  Yep, you might be able to get by with it a few times, but you'll have a ruined battery soon enough.

Please note:  a "10 amp-hour" lead-acid battery does not mean that you can run your CPAP machine for 10 hours.

There's numerous posts about this in other threads.  Wattage rating of a UPS is not the main factor.  It's all about the amp-hours of the lead-acid battery - the higher the better and most consumer-grade UPS have very low amp-hour batteries, as they're designed to keep your computer/router etc. up and running for a few minutes at best - enough time to save your work and shut down the system before power is lost.

Keep in mind, we're talking about lead-acid batteries, not lithium, SLA, NiMH or other types.  And lead-acid are the types used in most consumer-grade UPS devices.


Yep, a standard UPS might work for you once or twice, but you're ruining the battery in the process and it won't keep working for you if you have too many deep discharges.

If it were me, the minimum amp-hour rating I'd want for CPAP emergency use would be a 60 amp-hour lead-acid.  But I have a 105 currently, which works super.  Again, if you're only using it for an hour or two, then you can get by with less... but not for an entire night of CPAP use (without damaging the battery).

[horsepower]

A ups does not care what kind of devices are plugged into it... AC power, AMPs and Watts are all the same to the UPS... Does not matter if its a heater drawing the power or a big honking server.... Unless you are using the UPS as a power source while you are out camping, running on it all the time, using it as a power backup for when the power goes out will not damage the battery any more than it would if a computer was plugged into it.... They are designed to do what they do... If you only have 8 hours of power a day, and the rest of the time you are without power, then yes, it may not be good for the UPS... If you have a brown out here or there, or lose the power for a few minutes a couple times a month, thats what these things are designed for.

[SuperSleeper]

If you have a brown out here or there, or lose the power for a few minutes a couple times a month, thats what these things are designed for.

Exactly.  They are not designed for extended usage (like requiring them to power a CPAP machine for 8 hours).

Little interruptions that are short-lived (a few minutes or an hour), fine.  But that's all the consumer-grade UPS devices are designed for.

That said, I run my CPAP machine attached to a consumer-grade UPS. Not for an extended power-outage, but rather because most UPS devices provide excellent surge/spike protection. That's the real reason you might want to use a UPS (protect the device), not in order to power the CPAP for several hours.

More info here:

http://www.apneaboard.com/forums/Thread-...r-goes-out

[SuperSleeper]

Info from this post:

It's not the wattage of a backup power supply that matters, but the amp-hour rating of it's batteries.  Please see my post HERE on figuring how long a lead-acid battery will last and how to figure what amp-hour rating on a battery system you're going to need.   From what I've read, this UPS you mentioned is powered by two 8.5 amp-hour batteries, correct?  Most CPAPs without humidifiers draw about 1 amp per hour.  Add a humidifier and that can go up to 3 amps per hour or more (depending upon several factors).

I'm assuming those UPS batteries are maintenance-free sealed lead-acid like other similar UPS backups.  

Those two batteries add up to 17 amp hours and the formula is amp hours x 90% / hourly amperage draw, which will give you your max hours that will run your battery down to zero percent charge... but you should never run a lead-acid battery that far down (60 % max).  So with this Cyberpower UPS, the formula would be:

8.5 AH X 2 batteries = 17 total amp-hours

Then, it's 17 AH x 90% (Peukert's Equation factor) = 15.3 AH remaining.   Now if your CPAP draws 1.0 amp per hour, that would give you 15.3 hours of operation time, but there's a problem - that will take your battery down to zero percent charge... you can really only use up to 60% of a lead acid battery, otherwise you'll have a dead doorstop if you do that a few times.  So, that supposed 15.3 hours has to be reduced to give you the maximum safe discharge level...   15.3 X 60% = 9.48 hours in operating time... okay for one night on backup power, perhaps, now you have only 40% charge remaining.  While doing this will not kill your battery immediately, it will drastically reduce battery lifespan... Ideally, for optimum battery lifespan, it's recommended that you don't discharge a lead-acid battery down below a 70% charge.  This means that you really only can use 30% of your total capacity if you want to extend battery life.  This means that with the above system, you can only run your 1 amp-hour CPAP draw for 4.59 hours without risking poor battery lifespan.  Now, add to this factor a heated humidifier, and it gets worse... assuming you have a heated humidifier where both the CPAP and humidifier draw 3 amps per hour total, your ability to use this backup source for powering your system goes down to 1.45 hours... not a lot of time at all.

So, even a high quality UPS like the one you wrote about cannot power a CPAP with heated humidifier for an entire night of sleep, unless you're willing to destroy the batteries within the UPS.  Alternatively, a standard marine deep cycle battery like you get from the local Wal-Mart will power a CPAP easily for several nights before a charge is necessary... many of them are rated at over 100 amp-hours.

Now if you purchase one of those very expensive CPAP backup power systems that use a Lithium Ion Battery, then those are designed to handle a deeper discharge with no risk to battery lifespan... but I'm pretty sure most UPS systems come with lead-acid batteries, not Lithium Ion batteries.

and from here:

Batteries have Ampere Hour (AH) rating.  If you divide AH rating of the battery by the Amp rating your machine you will get the number of hours the battery will power your machine.  A 12Volt 120AH battery will last for 40 hours powering a CPAP machine rated at 12V 3Amp.

Not exactly:

Using that formula would assume that you're planning on depleting the battery completely down to a 0% charge, which is a big no-no with standard lead-acid type batteries that have liquid electrolytes sloshing around and lead fins (the "marine" or "deep cycle" car-sized type battery).

Roughly, 11.6 volts is considered fully discharged (0%).  You never want to do that to a standard lead-acid battery or you're ruin it.

Ideally, you want enough battery capacity so that you don't regularly discharge the battery much below 70-80% of capacity.  That will preserve battery life to a much greater extent.  Go below that 70% level too many times and battery lifespan decreases.  Go below 40% a few times and you have a doorstop instead of a battery.  In other words, in reality, you only have 60% of your battery capacity to work with (otherwise you risk ruining it).

The amp-hour rating for a battery is the maximum amps that can be drawn until the battery is completely discharged, over a specific time period.  The effective amp hours available drops as you draw more amps.  So a battery rated at 100 amp-hours (for instance) doesn't really have the capacity that the manufacturers claim.

Battery manufacturers do tests on the battery to give them an Amp-Hour rating.  A typical time period for a test is 20 hours, but it varies... batteries are tested over different periods, such as 24 hours, 75 hours, sometimes 100 hours.  Let's use a 100 amp -hour battery as example, just to make the numbers easier.... A 100 amp-hour battery tested over a 100 hour period (i.e. 1 amp drawn for 100 hours) will not have the same capacity as a 100 Amp-hour battery tested over a 20 hour period (i.e.-- 5 amps drawn for 20 hours)...  If you drew 1 amp continuously from a 20 hour test battery, it would last about 110-120% longer than on a 100 hour test battery.

Suppose you have a 100 amp-hour battery, tested over a 20 hour period. 100 Amp-hours divided by 20 hours = 5 amps. That means that the battery manufacturer claims the battery can sustain a 5 amp load for 20 hours until the battery is completely dead.

That's great, but wait... like I said, you don't want to drain a battery to it's completely dead 0%. On a lead-acid deep cycle battery, you should only drain a battery down to 40% of it's original capacity, absolute max. (in other words you've only got 60% of the battery to use).

On a 100 AH, 5 amp load, for instance... You have 20 hours of time at a 5 amp draw, but really you only have 60% of that time, so 20 hours x 60% = 12 hours.

Thus far, what I've said is true because I've used the same amperage over the same time period at which the battery was originally tested (20 hour rate). So what if you took your 100 amp-hour battery, but wanted to draw 10 amps from it until it was at the "safe" discharge level (say 60%)?

Do the math: 100 AH / 10 amps x 60% = 6 hours, right?  Wrong.

The More Amperage You Draw, the Lower the Battery Capacity.  So, the effective amp hours available drops the more amps you draw.  Now, that 100 amp-hour battery is not what it says it is.

Ok, now, using a 100 AH, 20 hour test battery, at 5 amps draw, you get the full 100% of the battery rating (that's how the battery was tested in the first place, so you should get all 100%). But step up the amperage to 10 amps, and you will lower the capacity of the battery by about 10% (or 90% remaining).

That makes 100 AH x 90% = 90 AH / 10 amps draw = 9 hours x 60% (max safe discharge number) = 5.4 hours. And that's a difference from the 6 hours you thought you had.

Where did I get the 90%?  It comes from Peukert's Equation...  that's where the approximate 90% comes from.  The Peukert Equation explains this... using it, you can predict how much time you'll actually have on a battery given a specific discharge rate.

The whole point is that the more you allow your lead-acid deep cycle battery to be discharged, the more you reduce your battery's lifespan.  Even though you can discharge it to low levels, it's probably not wise to do so, so buy a battery that has a relatively high amp-hour rating to begin with so you won't have to worry about discharging it too low and keep your battery charged up if you can rather than allowing it to go below 70% of charge (which is about 12.3 volts).  Keep in mind that I'm primarily talking about lead-acid deep cycle batteries.  Other battery types can be discharged to a greater extent, depending upon their design.

[OMyMyOHellYes]

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?