Modified UPS for Electrical Backup?

A UPS, that is usually used for computers, has advantages over an inverter. It automatically switches to the battery when power is lost, it includes a surge protector, and the battery is charged as needed.

Would modifying a UPS be a good idea for a CPAP?

Modifications could include:
Connecting a deep cell battery to the UPS. This could either be in parallel to the internal battery or as a replacement for the internal battery.
Adding a switch for the beeper. The beeper could be switched off during an outage. Another way would be to simply cut a wire going to the beeper, but then the beeper would never work.

The main thing I’m not sure about is can these supply power for hours? It seems like it could if it was sized big enough. The S9 has a 90 watt power supply. Would a 100 watt UPS be enough or should something higher like a 200 watt UPS be needed?

Another thing is to just buy the ResMed 12 to 24 volt converter, which would be more efficient. But that wouldn’t automatically switch over when power is lost. At around $90, I could buy a nice UPS. The UPS could be used with any CPAP. The ResMed converter would only work for ResMed S9's and possibly some others. With a UPS, I could also power my clock radio when there is a power outage.

Your thoughts on this?
Thanks,
Ed M.

What I use is an BackUPS 1100 here. If the power goes off the alarm on the UPS, the APAP and the Oxygen Concentrator all go off and I awaken and remove the humidifier, which is the largest consumer of current/power. The APAP on its own will last through the night, no problem, without the humidifier. Do your calculations removing the humidifier from the equation.

edm_msu wrote:Your thoughts on this?

Why re-invent the power supply?
viewtopic.php?f=1&t=64943&p=695301#p695301

Here is the thread you want.
viewtopic/t74956/viewtopic.php?f=1&t=73 ... ry#p671658

Thanks for both of the links! This is a good idea.

Before I posted, I did a search for "UPS" and nothing came up. Both of these posts have the term "UPS" in them so the search did not properly work.

Ed M.

edm_msu wrote:Before I posted, I did a search for "UPS" and nothing came up. Both of these posts have the term "UPS" in them so the search did not properly work.

Search for "battery" since using DC will give much more time than UPS..

Or you could use Google using the syntax "My Search Word" cpaptalk.com will direct google to search this forum with surprising results.

fwiw- My jump starter allows me to sleep right thru any outage thus far. Which is fine with me cuz I know IF I do wake up, I won't be able to get back to sleep "until the power comes back ON". Unless I have to leave the house I prefer to keep my sleep schedule.

Also before the jump starter any time the power went out I would wake right up. Not sure what causes that but I do wake right up.

First you would need at least a 300 watt UPS if you use a humidifier. I used a 1200W UPS for my computer modems, Router, and server. I bought it used with dead batteries for $10.00. After removing the two batteries and extending the battery cables I hooked up two 125Amp/hr deep cycle marine batteries in series, most UPS use 24Volts. The first year we had a ice storm here in the middle of the winter and I was without power for five days. This rig supplied power for the modems, router, and occasional use of the server and printer, along with charging and running our two laptops for the entire 5 days, it was a sure God send to us. The batteries only lasted for only two years because the built in float charger, was expecting AGM batteries which have a different and higher voltage charging profile. would constantly over charge the batteries. I didn't at the time realize how bad it was ruining the batteries.
After the batteries died I hooked up two cheap lawn tractor batteries, 30 Amp/hr. they seemed a better match for the charger as they lasted over 2 1/2 years at 1/4 the cost. Since I have moved, I haven't hooked them up yet at our new house, but I plan to do this soon as now here we have to have a internet link for our cell phones to work in our house along with the internet. So if you go this route, I would recommend getting two Deep Cycle AGM batteries, a couple of 50 Amp/hr batteries should give you easily about four nights worth of CPAP.
I currently use a 125 Amp/hr Deep Cycle Marine battery, with a "BatteryTender" float charger to directly power my CPAP for the last three years, with no problems. We get at least four or five power outages a year here and I would not be without it!

If money were no object you could just purchase a high end UPS. The problem is that most units not designed for 'server' use use a 'step approximated sine wave' which is not compatible with a CPAP. If you buy a dead UPS you must make sure the output is a pure sine wave. Luckily the newer high efficiency PCs are starting to not like the 'step approximation' so the price on 'pure sine' units is going down. I just haven't found the spare cash to buy one. You certainly won't get multi-day run times like deep cycles but if you only have short outages like I do I think a pure sine UPS is the way to go.

KrisasMan wrote:a 'step approximated sine wave' which is not compatible with a CPAP.

Luckily, when using DC you don't have to worry about that or the conversion loss or the loss of cash.

For those cpap users who don't understand all of this IF you try to use a UPS - the battery DC is convert to AC where a loss of power occurs. The the cpap power adapter converts that AC back to DC so it can be used by the cpap machine.

You might get 30 minutes out of your average UPS because a UPS is designed to just run the computer equipment long enuff to be powered down logically. A quick "power interruption" can cause damage.

So a UPS smooths out any power interruptions until is can be shutdown logically.

KrisasMan wrote:If money were no object you could just purchase a high end UPS.

It's not only more economical but makes more sense to use DC (battery power) since that IS what your cpap machine wants to use.

But it is your cash and you can do whatever YOU want with it

The only issue there is that not every CPAP can take DC input. Considering the size of my Icon I have wondered if it uses an AC motor and heating element and then has an tiny internal AC/DC adapter for the electronics (which always must be DC). Then again maybe the variable speed blower of a CPAP requires DC?

KrisasMan wrote:The only issue there is that not every CPAP can take DC input. Considering the size of my Icon I have wondered if it uses an AC motor and heating element and then has an tiny internal AC/DC adapter for the electronics (which always must be DC). Then again maybe the variable speed blower of a CPAP requires DC?

Don't get me going about a real cpap machine. I think that is how they save money by leaving things out.

But I will say I think it is probably more affordable and definitely more convenient to just buy a cpap machine that will work from 12V DC rather than play around converting voltages to do something the manufacturer did not include in the design.

Let's face it, most cpap manufacturers do include the DC option and the smart ones use a voltage that is more commonly found in every auto made. Most are 12 volt not 24 volts requiring additional conversions.

So if you live in an area that you need to think about alternate power sources then think what alternate power you will use and buy a machine that will use that power source.

You wouldn't buy a diesel powered car if diesel was not available near your home? Or would you?

Been there . . . done that . . . built the UPS-ZILLA!

viewtopic.php?f=1&t=73063&p=671621&hilit=belkin#p671485



Essentially, I just bypassed the internal battery and connected the battery connectors to an external deep-cycle lead acid battery. It works great. Quiet, unobtrusive, works with only a barely audible "tick" when the relay closes. Can't hear it unless I'm listening for it.

The ResMed S9 with H5i can use a modified sine wave inverter. The ResMed DC to DC converter costs around $90. After considerable thouoght, I decided to go with a single battery UPS. If the power goes out in the middle of the night, the CPAP will not be interupted. Last year we lost power for at least 3 hours at least 10 times. The UPS can be used for many things, the DC to DC converter can only be used for one thing. The UPS can be hooked up to my clock radio and my nightstand light so it is more versatile. The DC to DC converter is more effieient, but I believe the advantages of the UPS out weigh this.

A single battery UPS will be used because a single 12 VDC deep cycle battery can be hooked up. A dual cell UPS needs 24 VDC so two deep cell batteries would be needed.

I appreciate everyone's replies. All of them were helpful.
Ed M.

ResMed publishes that S9 CPAP with or without humidifier will work OK on MSW (Modified Sine Wave.)

They say that MSW will damage an S8 humidifier. S8 CPAP without humidifier is OK.

I don't think I've seen an official statement from Respironics, but it seems likely that the PRS1 machines that power the humidifier off DC from the power brick would be OK, and older models that power the humidifier off AC wouldn't be OK with MSW. I'd be willing to take that risk with my own equipment if necessary. Of course, you're on your own if you try it and it blows up your CPAP. Of course, on Respironics, you don't have to have that expensive DC-DC converter that ResMed wants you to use.

Over the years I acquired 4 UPS systems. They work great when used for the intended purpose which is short durations. I use 1 for desktop computer, 1 for my DSL modem,, 1 for the DDR & TV, another sits unused.

I am sure if this doesn't work for your cpap you will find another use for the UPS.

When I am home and the power is off more than a few minutes I shut them OFF so as to not drain the very pricey batteries.

When I wanted a backup power source for my cpap I started with a $25 jump starter I already had to see if it would work. I was told I was "OFF My Rocker" but that is the Betty White's show on NBC tonite (@ 8 EDT).

I was lucky enuff to have a cpap that had a DC connector, NO Data but it did have a DC connector. Today, I would NOT buy a machine w/o either. I made my own DC cord from Radio Shack parts for about $10.

What I wanted to say is the secret(s) to this jump starter thingy is to keep it plugged in and charging AND to have more than one. I had plenty of use for them last year when the power was off for 3-4 days twice. The 1st time was right after I bought a battery to fix a jump starter a friend gave me. Until then I only had one jump starter.

Believe me when I say it, having a backup plan for your cpap is like having a fire extinguisher. When you need it, you won't have time to go buy it. IF it turns out that you NEVER need it, well isn't that why we buy insurance?

Don't forget "OFF Their Rockers" Tonite at 8PM EST.
http://www.nbc.com/betty-whites-off-their-rockers/