Do-it-yourself UPS 388
Giampiero writes "Over at dansdata.com some guy named Dan creates a UPS out of some spare parts. To sum it up, "if you're looking for an industrial-capacity UPS solution, and don't like the prices of the off-the-peg options, it might be easier than you think to roll your own."" Of course you can mentally substitute U.S. 110 volts for Australian 220 volts wherever necessary...
Cheap UPS (Score:2, Informative)
Somehow, I get the nagging feeling that this pristine condition UPS (that I'm using right now) was worth more than $10
Basically what I've got for my emergency radio (Score:5, Informative)
Put a "battery isolator", or at least a power diode with a heat sink, between the power supply and the battery. And allow for the fact that it will drop
Don't even think about wet cells inside the house. Sulfuric acid belongs out of doors. There's a reason you're allowed to ship the Concorde battery without declaring it hazardous: it won't spill. Further, a non-sealed battery will release hydrogen while it's being recharged. Is your computer room free of all ignition sources?
Fred KC7YRN
(I've seen a commercial 500 VA unit for US$40)
Re:Why convert DC to AC to DC? (Score:3, Informative)
Yes, you could work around this without going to AC, but it's easier and more flexible to just provide AC and let the power supply worry about the rest.
Re:Be Careful (Score:5, Informative)
I could hold a 1 volt 300000 amp power supply's leads all day and not be hurt. The reason is Ohms law.
Your body generally has a pretty high resistance. Ohms law states that amps=volts/resistance. Your body is probably between 20,000 and 300,000 ohms, depending on which part you are talking about. Wet or sweaty parts have lower resistance. Higher voltage is more dangerous, because more amps will flow through your body. A 500 volt at 1 amp power supply would probably be lethal, especially if you had wet hands.
A rule of thumb is that anything above 50 volts should be treated very carefully. This is about the threshold of where you will normally start to conduct possibly dangerous amounts of current. If your hands are sweaty or wet, or you are grounded well for some reason, better cut that down to 30 volts.
Here's a link [asu.edu]
The parent post is correct though, be careful in any case. Don't try this stuff unless you know what you are doing around electricity.
Australian Voltage (Score:1, Informative)
Isn't Australian mains Voltage 240v not 220v
speaking of conversion... (Score:3, Informative)
Re:Expanding batteries (Score:2, Informative)
Also, running non-sealed batteries indoors can be dangerous. Putting them in a box outside and running wires in would be best. It also allows for more expansion, and solar charging systems.
The Remains (Score:5, Informative)
Now this wasn't your home little ups box, this thing would blend in with three refrigerators side by side, and would run a 500 person electronics factory, and 500 person office (PC's at least) for 8+ hours. That was a kickass battery box.
Just remember, UPS's can go "BOOM" and I wouldn't want to try my hand at making my own and seeing it for myself. Some things are better left to APC and crue.
-Pete
Re:Why convert DC to AC to DC? (Score:3, Informative)
As a tip, if you need alot of voltage for a fan, you can splice the -12v going into the mobo, and put the fan between that line and a +5 or +12 to get a potential of 17v or 24v to run your fans off of. My Athlon almost runs at non-nuclear temps using this trick.
Comment removed (Score:3, Informative)
Re:Awesome! (Score:2, Informative)
I have a 24 and 36 volt inverters. To add additional capacity all I need to do is add more batteries. The only thing to make sure is that ther e is proper ventalation for the batteries.
The inverters have ports for remote management as well as status leds.
It is a much lower cost solution and not as risky as there is not really high voltages.
Re:Fixing APC Smart Rack UPS (Score:3, Informative)
However, you can probably replace the battery in your UPS with a similar model for less than the cost of a new UPS. Either find the manual for your UPS, search for your UPS model on line, or open up your UPS and see if it has any labelling regarding the battery capacity, or (better) a "replace battery with XXXXXX model or equivalent." Find an equivalent on line (thanks, Google!)
Check with a battery store (most major metropolitan areas will have several.) It may be worth the drive, as batteries are heavy, cost much to ship, and can only be delivered via ground (slowly.) And if you're uncomfortable working with live circuits or very hazardous materials, they'll probably be able to replace it for you for a small fee.
Finally, PLEASE RECYCLE YOUR OLD BATTERY! In most states, it is illegal to dispose of any lead acid batteries in the garbage or in a landfill. They are filled with corrosive toxic sludge. Please be responsible.
http://auction.apc.com/ (Score:5, Informative)
http://auction.apc.com/
And get refurbished, and sometimes brand-new, warranteed APC power units for pennies on the dollar.
Two years ago I purchased two 420VA refurbished backups for around $50 each. They're currently protecting my three boxen, one of which I'm on now, and have been flawlessly through brown-outs, sags, surges, etc.
Typically the refurb'd units are from companies who have agreements with APC to buy many UPSs and return them when the batteries run out. Why? Customers used to return UPSs marked as 'defective' when in fact it was simply a dead battery. So, they tape over the battery bay and simply have the customers return the units with dead batteries and pick up a new one. They replace the battery and sell the ok unit again as refurbished.
Re:Be Careful (Score:3, Informative)
I haven't measured it, but it felt like 110VAC across the prongs to me when I discovered this effect by accident. Be very careful with these things...
Re:Basically what I've got for my emergency radio (Score:3, Informative)
Some power supplies (even some fancy lab power supplies - I've seen people kill them this way) don't have a diode on their outputs, so if you turn off the supply (or, say, the power goes out), then the battery will attempt to put energy into the power supply. If the power supply isn't made for this, it could smoke and/or catch fire. A diode ensures that power only goes *into* the battery. Put the cathode end (with the band, "negative") towards the + side of the battery, with the anode (the other end of the diode) towards the + side of the power supply. Make sure that the diode can handle the current (most diodes drop ~0.7v, so dissappated power=I*E=Charging current * 0.7v)
Second, I'd be really cautious about putting power supplies in parallel to achieve more current. While this will usually work, the same problem exists that exists: power supplies don't always behave well when connected to another supply. With one diode isolating each power supply and current-limiting supplies, this should work safely, but the voltage regulation may be poor and the supplies may not share equaly - things not of great importance here. The general problem in paralleling output transistors is that, depending on the circuit, increased temperature can lower the resistance of the transistor, which causes more current to flow through it (relative to the other transistors in parallel), which causes more heat, etc... until it blows (or the current limiting of the supply kicks in).
For another project, I wonder about UPS modding. I've got a UPS that puts out the right amount of power, but the battery is kindof small. It seems that I could replace it with a higher capacity car or motorcycle battery of the same voltage.
Old Old Old Old (Score:2, Informative)
On another note, one of the nice things about this is the ability to expand the source of the 12v in. For instance, a small array of solar cells wired together and into the battery taking the load off of the house current/AC->DC thingy during some days. When we did the math for it, it paid for it's self in about 4 month of sunlight every day, or about a year in real life. 12v is a nice little voltage to work with when it comes to this and alternitive energy sources. Hell, wire a nice little 12v DC generator to an exercise bike for when your bored. Get a work out and save on your electric bill. Also, if you want to go real insane/creative, suck off of the telephone lines when not in use, they got something comming through them i'm sure. It's alot easier to get 12volts then it is 110ac.
Re:Be Careful (Score:3, Informative)
A more paranoid approach is to check wattages
Cue the story of the navy engineer that killed himself with a muultimeter (runs on a 9V). See, he wanted to measure his internal resistance (which was fairly low), so he held the leads, one in each hand, and punctured his thumbs. Long story short, he discovered that 80mA across the heart = 1 dead Seaman.
220Volts (Score:2, Informative)
Re:Myth. (Score:3, Informative)
You don't need to be paranoid when working with lethal voltages... but you do need an ounce of common sense. Work with one hand.
(Cue web surfing while masturbating joke here - but I'm quite serious.)
Some words of advice on UPSes (Score:5, Informative)
The smallest unit I have is a 600VA no-name Taiwanese box with two 7A SLAs. It has no fan and, although it's just an SBS, it still runs hot as hell.
As a result of this hot running, I discovered that the SLAs tend to dry out rather quickly such that you get a much shorter time than you'd expect when the mains power goes off (as I discovered just the other night
My other box is a Siemens 1KVA full-time UPS with forced ventilation and a bunch of other cool features.
It's worth noting that even a fan-cooled UPS such as the Siemens can run way too hot -- as I discovered about a year after I installed it.
Without warning, the UPS started screeming at me with a continuous alarm buzzer. It was still working but it was not at all happy.
On touching the case I discovered why -- it was too hot to touch.
I shut things down really quickly and opened up the case to see what was wrong...
Dust!
The intake holes in the front panel have a fine wire mesh over them and, since this UPS (like most others) lives on the floor under my desk, enough dust had been sucked into the holes to totally block them.
So here's a DC-AC inverter busy delivering about 500W of power to several computers and monitors -- but without the benefit of any cooling. No wonder it wasn't happy.
I blew the filters out with compressed air, checked that the fan was okay and put it back together. It's been working fine for nearly two years since -- albeit that I check and clean the intake meshes every few months now.
That the Siemens box was smart enough to warn me it was in distress (rather than just failing) shows that nobody ever regretted buying quality.
So.. rules of thumb for UPSes...
If it runs hot-- expect the batteries to last just 18 months to 2 years -- and don't wait until the power fails to find out that you should have changed them already.
If you have a fan-cooled UPS mount it up off the floor or check that the cooling holes are clear at regular intervals.
Comment removed (Score:3, Informative)
Re:Awesome! (Score:3, Informative)
To a large extent the danger of explosion can be reduced by using hydrogen catalyst battery caps on all cells of the lead acid battery. These can be purchased from Hydrocap, 975 N.W. 95 Street, Miami Florida, 33150,(305)696-2504.
Re:Fixing APC Smart Rack UPS (Score:3, Informative)
UPS batteries tend not to be as expensive as notebook batteries...there aren't as many different varieties, so they tend to be somewhat standardized. I recently replaced the two 12V 7Ah batteries in a UPS at home. That UPS cost about $170 when I bought it. New batteries were about $40 for two. Given that the UPS is a 900VA unit that can keep a dual-P!!! server running for about half an hour, $40 isn't a bad deal to keep it running.
beowulf cluster batteries? (Score:3, Informative)
We got a UPS because it has a good inverter and auto switching and a built in charger. An inverter would have cost more. I've got a snmp card so I can measure different things.
You have to be careful about these things beause you get a large voltage and massive amounts of current. Our system has two 96 volt banks and good for at least 300 amps. That can kill and it can also cause batteries to explode. Treat these with the respect they deserve. We have a small circut that goes between each battery that has 4 led's that let us know if any one of the batteries go bad. Its also hooked to a monitor system so we can get real time alarms if anything goes bad.
One word of warning... (Score:2, Informative)
I used to design UPS's for a major American UPS mfr. The author slightly mentioned that you would not want to use a normal UPS for continuous operation due to overheating. He is correct but for the wrong reason. It is NOT overheating of the battery cables you have to worry about. It is the Transformer.
Since the Transformer is the biggest cost item next to the Battery they are highly optimized for the performance/price point. That means a transformer designed to run at 400VA for 3 minutes will probably melt into a glob of laquer, copper, and steel in about 20 minutes. Of course that also means it could short out, catch fire, or send unknown voltages to your computer possibly destroying your computer PS.
Just as a point of reference the industry has made a distinction between continuous duty and back-up supplies. UPS means temporary supply to allow you to save data. Inverter means continous duty.
If you wish to try this project I make two suggestions:
1. Use or purchase an Inverter. Tripp Lite sells the PV series inverters which were designed to be used exactly in the fashion of the unit in that article. They also sell APS's which are UPS's that _are_ continous duty.
2. If you MUST use a UPS inverter, then get one that is overrated by at least 10 to 1 in VA handling capability. Depending on the UPS you get this may not be enough, but it will get you close.
3. If you are really ambitious, replace the UPS transformer with a much bigger one. Keep in mind that the power handling of the drive circuitry is important too, but hey - you want to tinker, right? Just make sure you understand the proper step-up ratio and winding configuration of the original transformer.
Re:Myth. (Score:1, Informative)
Alligator clip leads.