UPS-ZILLA! (UPS Uninterruptable Power Supply)

JohnBFisher has done a great job documenting how to assemble an uninterruptable power supply for a CPAP machine. This afternoon I put something similar together using a recycled computer UPS, a deep cycle battery and a battery box.

Last night we had three power outages, each about 10-20 minutes in length. A couple nights earlier power was out for 6 hours. No explanation for it. Weather's been fine in coastal Southern California. But last night was the last straw. I really don't like not having my CPAP. I feel awful the next morning, can't function at work, etc.

This afternoon I brought home an old computer UPS that one of my coworkers was throwing out. People commonly throw these things away and buy new ones rather than spend $30 and five minutes replacing the internal battery. This one, a Belkin 750VA had been lying under my desk for several months. I didn't know what I was going to do with it, since I already have a UPS connected to my work computer. But the thing was too expensive and potentially useful to simply send to the recyclers.

I stopped by a battery shoppe and picked up a Group 24 deep cycle battery and a box for $75 total. When I got home I removed the old battery from the UPS and wired the battery connectors to binding posts that I mounted on the former battery compartment door. Disassembled the case, located and destroyed the annoying little beeper, then reassembled and connected the battery to the binding posts. Fired it up and was rewarded with a subdued relay click and a green light as the electronics came to life. Success!

The UPS had a 7AH lead-acid battery which would be sufficient to power an S9 Autoset with humidifier running for half an hour or so. Problem is, each time you discharge a lead acid battery more than 50% of its capacity, you shorten its life dramatically. The damage is cumulative. The life of a UPS battery is harsh, brutal and short. A half dozen power outages which drain the battery past 50% charge is about all it's good for. However, by replacing the battery with one 10 times as large, such as a Group 24 battery, available most anywhere, one can operate much longer and not damage the battery. The on-board charger is sized to charge and maintain a 7 AH battery. It should be sufficient to maintain the larger deep cycle battery, but I'll watch the terminal voltage to make sure.

Here's a couple pics:





I still need to clean up the wires; this was taken five minutes after hooking everything up.
Looking forward to uninterrupted sleep from now on.

SBF

Is that an electric meter on the nightstand?

Looks good though. I went with an off-the shelf model myself, only does 30 min, but the alarm wakes me up to let me know I should wait for the power to come back on. Here where I live that's typically not more than an hour at a shot, a few times a year though.

Hose recycle idea....I have used an old hose to hide wires. Take a scissors and cut the hose along the length to the size you need and fit the wires inside. Mine runs along the base board.

TalonNYC wrote:Is that an electric meter on the nightstand?

Looks good though. I went with an off-the shelf model myself, only does 30 min, but the alarm wakes me up to let me know I should wait for the power to come back on. Here where I live that's typically not more than an hour at a shot, a few times a year though.

Yes, a friend works for a utility that was swapping out the old meters for the new electronic ones and gave me that one, so I made it into a lamp. It actually works.

The reason for the mod to the UPS was so that I wouldn't be awakened if power went off during the night. With the larger battery now I can just sleep through it.

How often does the power go out in sunny southern California?
We get a night about every two years, and ten years ago, we had a whole week.

Good idea! So are you running through it all the time?

Chunky: Power goes out at least once/month, but often during the night I'll hear the computer UPS in the other room beep indicating some sort of interruption. Outages usually last only minutes, sometimes tens of minutes, sometimes longer. Our power comes to us along a narrow twisty canyon road that's lined with telephone poles, each of which seems to be a tempting target for drunk/texting drivers. Someone a long time ago thought it would be good to build a road in what was, and is occasionally, a streambed. So when it rains . . . You get the idea. So that's why the UPS was necessary.

Liz, yes, the UPS is used just like a power strip. Everything you want protected from power outages is plugged into it. In my case, that's the desk lamp and CPAP machine. The desk lamp has a receptacle on the back that the CPAP and alarm clock plugs into. So during a power outage the UPS takes over and runs off battery power without even a flicker until power is restored. Then the battery is automatically recharged and held ready until the next power outage.

I thought maybe you were still feeling the effects of enron.

I don't know anything about these. What are the minimum specs required for the UPS? The earlier conversations on this went way over my head. But I did find this: http://www.jkovach.net/projects/powerquality/
Your setup looks easy. I want to start watching Craigslist. I found an old post for an APC Smart UPS 700. Those look alot larger than yours. It says 450 W / 700 VA. I assume there is a maximum that the inverter can handle?

This one happens to be a Belkin 750VA. Presumably that means it can handle a resistive load of 750 watts (for a very short time) so running a CPAP machine at less than 100 watts should be no problem. A typical computer system runs somewhere around 100-200 watts. I also have an APC 500 and 650 on my computers, and either of those would have worked fine, but the APC tends to make more noise than the Belkin, so I used the latter.

Thanks. Glad you added the description to the title. I almost didn't read it until I saw it was you.

I noticed my machine used about 60 watts while it was warming up the water in the reservoir. Then, overnight it used an average of 32 watts. That's about 3 amps at 12 volts which would take a 7 amp hour UPS battery below the 50% charge level in about an hour. Having the larger battery capacity moves that point well past wake-up time and lets folks like me make it through the night and get to work without dealing with power-related issues during the night.

For those of us with S9s which require 24volts to run on, running straight battery backup isn't really an option. Some sort of inverter is needed. Rather than hooking up an external inverter and dealing with the complexity, I figured I'd opt for an already packaged computer uninterruptable power supply (UPS). Besides, it was free, except for the battery

Now, if I had only an Intellipap*, which runs on 12 volts DC, simply running on a battery would be the preferred solution.

*Actually, I do, but that one is at the wife's near Seattle.

Great idea! I'm gonna make two of these so we can just sleep through the outages and protect our machines from surges.

Glad you liked it. It's simple and easy to make and solves the problem of needing an inverter and battery charger, and it keeps my alarm clock from losing its time, too.

My biggest concern is protecting the expensive CPAP from power surges and other mains problems. The battery is just the icing on that cake. I have old UPS's laying aournd that I had been thinking about getting replacement batteries for, but my wife replaces them with all new units. Now I have a very good use for them.

thank you!

Dan, I expect you already know that's what a UPS is really for. Protecting computers against poor unfiltered power, power spikes, brownouts and power interruptions. Outside of feeding your machine DC from a battery, the power from a UPS is about as clean as it's going to get. Since you, too, have access to several old UPSs, try each one and choose the one that runs the quietest. My APCs make an audible buzzing, while the Belkin was utterly silent. Well, at least it became silent after I snipped the lead to the beeper on the circuit board. Now when we lose power I can hear the APC at the other end of the house beeping, and I'm totally unaware that the Belkin is doing anything at all. However my S9 Autoset is still blowing air and the alarm clock still says it's not yet time to get up. The sound of the other UPSs in the house isn't loud enough to disturb me, just enough to be aware of.

I'm glad you were able to make use of my suggestion.

Sleep well!