Do-it-yourself UPS

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...

Comments

Be Careful

[TibbonZero]

Please, everyone take caution when working with high voltage and moreso, high ampre compenents. We don't want any fried ./ers

Re:Be Careful

[GigsVT]

People often misunderstand the electrocution hazards presented by electricity. Yes, technically it's the amps that hurt you, but the volts have to be there too.

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

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.

Re:Be Careful

[stienman]

This indicates that something is seriously wrong with your UPS. If it did drive a current or voltage across the input power plugs it'd be powering the building grid which is not only illegal, but those doing so are liable for any damage to the power grid and associated line workers. They take just as much protection for a downed grid as a live one for stupid users who try to power a downed grid, but several die each year because someone's power went out and their generator/UPS/alternative power system was back feeding the utility company when the grid was down. Connecting two mismatched live grids together is fun for the whole family.

If your UPS is UL listed then there are several regulations which govern just this sort of action. Report the problem to APC, if they don't do anything about it (!!!) then report it to the UL and/or BBB.

I'm being completely serious. For it to go this bad there is certian to be more wrong with it. I wouldn't trust it to power anything worth more than $10.

-Adam

Do it yourself UPS?

[Anonymous Coward]

I for one do not have time to truck all my packages individually across the country!

Oh ... um ... never mind.

Do-it-yourself UPS? It's been done.

[TheFrood]

I've been doing this for years. I have a big brown truck, and whenever I want to send something to someone else, I just put it in a box, hop in the truck, and drive it over to them. I've even got a little portable touchpad for them to sign on, so it feels like the real thing.

TheFrood

I don't know...

[bravehamster]

..."rolling my own" world-wide shipping conglomerate sounds like a little too much work to save a few bucks on shipping. I'll just stick with Pullman Brown, thank you very much.

On the other hand, would I get to wear the little shorts? Chicks seem to dig those.

Why convert DC to AC to DC?

[cyberformer]

A major part of the description on the site (and the cost of a "real" UPS) is how to convert the DC output of a UPS to the AC power required by most PCs.

Of course, PCs don't actually use AC power: there's a big box in the back that converts all the AC input back to DC. So why not save some money and bypass this, by running the PC straight off the battery (like a laptop)?

Re:Why convert DC to AC to DC?

[steveha]

I have, for years, wished for a DC input on the PC's power supply, and a standard for UPSes that would plug in to that DC input.

Taking DC, converting to AC so the PC power supply is happy, then the power supply converts to DC... it would be nice if it could just be DC all the way.

The problem is that your monitor, modem, etc. all expect AC power. It's easiest just to make a UPS that provides standard AC power, and plug everything in.

Someday, I think we will have "smart" plugs. Wall power outlets will not be live by default; they will only serve power when a proper coded request goes in over a smart plug. The device will be able to tell the wall outlet what kind of power it wants, and the outlet will be able to tell the device what kinds of power it can offer. Then little kids will stick butter knives into wall outlets and not get fried; PCs and monitors will ask for +5 and +12 volts DC and get it; and UPSes will be able to feed +5 and +12 volts DC to those PCs and monitors.

Actually, if you have the complicated smart power system I envision, there will probably be a UPS integral to the system. When your home loses power, the smart power system would broadcast a "power interrupted" signal and devices like your refrigerator and your laser printer will power themselves down; your PC will run for about 5 minutes and then power itself down (unless you are there and override it) and medical devices will run indefinitely. Maybe only the DC devices in your home will be on the UPS by default?

steveha

Basically what I've got for my emergency radio

[Beryllium Sphere(tm)]

Coupla caveats:

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 .3 or .7 volts.

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:Expanding batteries

[El_Nofx]

When I did tech support for Gateway I got a guy who worked for APC, he had a UPS on his Fridge, his microwave, his TV, his stereo, and his pc but forgot to protect his phone line, Lightning struck by his house and took out his modem, along with his mobo. After he told me all that I laughed so hard he hung up, I wonder what ever happened to him, hehe

The Remains

[peterdaly]

Be careful with this stuff. Batteries can be nasty. At my previous job we had a "switch room" which housed out 50,000kva (yes "K"va) UPS. On the wall across from it were huge "grab the handle and yank" circuit breakers...which were covered in battery acid from the previous UPS.

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

http://auction.apc.com/

[MattRog]

Or, you could visit:
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:Do-it-yourself UPS? It's been done.

[Fulcrum of Evil]

I've even got a little portable touchpad for them to sign on, so it feels like the real thing.

If you really want it to feel like UPS Ground, shouldn't you kick the box around the back of the truck en route?

Some words of advice on UPSes

[NewtonsLaw]

I have two UPSes -- I used to have three but one died a horrible death for no apparent reason.

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.