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The easy part is getting batteries stacked, wired, charged.
Still easy is to power up 12V devices from that: I was thinking a zener diode, regulator, capacitor between battery back and 12V DC sources, so trickle charges can continue normal operation like no load was attached while beyond the regulator etc. is a 12V PSU with 12V devices. and when network electricity goes the trickle charger, 12V PSUs shutdown and 12V devices get powered from the battery pack with regulator +capacitor "cleaned" source.
Some kind surge protector + fuses might be still good idea tho.

The problem arises on how to switch between inverters and network electricity on 230V equipment?
How to "join" together multiple cheap inverters for single source of 230V instead of calculating how much to put behind each single inverter?
I've heard of switches sold for this usage for rack mounting, but i simply cannot find those "STS switches" for sale. Or would SPDT relays switch fast enough when outage occurs? Doesn't that cause spikes, and need something to smooth out the transition?

One problem tho remains at this location is how to clean the network electricity, as it's a bit flaky there, short sub second outages are known to happen there during storms and fuses to blow with no apparent reason occasionally. Network -> converter -> battery back -> inverter -> miners is just not a feasible option due to losses.

I'd like to see a UPS capable of sustaining a serious mining farm during a blackout. It would have like 50 car batteries lol :p. Imagine an electrical fire or some other mishap then! rofl

Single car battery is able to supply 720W for an hour, in theory. In practice more like 600W before voltage drops too low and due to the age of the battery.
5 for full 16A 230V circuit for an hour.

In other words, that single battery is sufficient for a single 4x7970 rig @ ~2Ghash... Or 1 hour for 10Ghash. Most power outages are solved within that time.

Plus the batteries are free :P

Capacitor?  Big ones? Lots of them?

The bad news is one capable of providing the necessary current during the transition are likely very very expensive.

220V, 220uF $900+  :(  More like $1 (I can't read).

http://search.digikey.com/us/en/products/SLP221M220A1P3/SLP221M220A1P3-ND/1882197

That seems to be a lot of 1000 or more.
I was more thinking like couple of these lil' puppies: http://www.sonicelectronix.com/item_21166_Power-Acoustik-PC1.5F.html

WOW that is cheap, was more like expecting 100€ a piece, just result on google :P

Well they make UPS capable of sustaining entire datacenters during power outages.  If you got enough $$$ you can get just about anything.

http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=SYA16K16PXR&total_watts=10000

Yeah that was my first thought from my younger years and car stereo (what a waste of money, lolz).  The issue is they are 24V DC.  Not sure how they would fit into your wiring. 

My thinking (and it may be wrong) is you need to do four things

a) buffer the 120V/240V feed from power grid <- cap goes here
b) detect input power drop and disconnect protected loads from mains to battery bank (cap in A will continue to power load until switch occurs)
c) have trickle charge system to have battery bank loaded at all times
d) have sufficient inverter capacity to convert DC to AC to power protected gear.

For part D I am thinking a small solar power inverter is likely ideal.  Right?  DC in -> 120V/240V AC out.  Can wire it right into a sub panel and connect it to a bank of protected circuits.

Oh yeah, the reason to add capacitors is just to smooth spikes out, batteries aren't exactly good at handling big current spikes.

The real question is how to handle transition from network power to inverters in case of power failure. That's the only thing i need to really solve still, rest is up for building and testing, see how well it works, or how poorly it works :)

for AC you can't exactly add capacitors so SPDT relays might not come into question...

And they are here 12V not 24V. Using capacitor for just 12V is not a problem at all btw.
You can always utilize one for lower voltage than it's rating is for, and it does not change the capacitance.

You can put caps on AC, but it is much more difficult to properly implement without them blowing up and stuff. They would be there to provide a way of transitioning between inverters, or from AC to inverter without causing massive brownouts and spikes.

I've got no experience of caps on AC, and would assume usage of them is freakishly complicated, seeing AC is a sinewave and a capacitor is meant to smooth out voltage fluctuation ...

The question really is then -> how big are the caps on high quality seasonic (and derivative) PSUs ... Some server PSUs have so huge capacitors they can take 5+ seconds of power outage without the system crashing ... Tho last PSU like that i've had the pleasure to use was built for 386 era server ... (The case+PSU alone weighted over 30kg ...)
most likely not big enough to sustain that kind of loads for the period it takes SPDTs to change and inverters to "gear up" for the output.

My understanding on capacitors is that disc types (solid state) work with AC

Electrolytic do as well, for instance think start/run caps on single-phase motors. In those applications, they are used to shift a single phase 90 degrees or so in order to start or run a motor.

I'd like a guide on actually building a UPS so I can make plans that suit the needs of my computers (2 at the moment).
My PC is used as the main mining/gaming rig.My MBP is used as a complementary miner/main filmmaking rig. Since my PC draws around ~285W from the wall (with HD6950 heavily OC'd/unlocked shaders) (PC Idles around 85W when doing nothing).

MBP uses about 90W (cpu full load for film editing,GPU for mining BTC) under full load.
Outlets use 240V in UK (so will need a converter as Apple's car/airplane lead doesn't charge my MBP,just powers it and if the machine is using more than 75W which it does,then the battery drains as well as just being powered by the car/airplane lead.)

I wonder what setup I'd need to sustain say nearly 400W (typical) or 550W (peak from my 2 computers) for around 2 hours (as that seems to be when most utilities manage to get thing sup and running again,in UK this can take longer in some parts)

take a traditional, used, otherwise functional but battery dead APC backups, replace the batteries with 2xcar batteries. Just make sure it's rated for atleast 700w load.
Easy for small load like that :)

FWIW, my electrician said he can get me a functioning (read used) 36Kw UPS for $4k. That would run my farm for at least a couple of hours before running out of juice.

Question is how often do you encounter power outages to make it worth buying this UPS. Also, how much would you make during those few hours.
Also, if you decide to buy it, make sure to check the state of the batteries.

You have hit the nail on the head. My power has gone out once in the last six months and it was for less than one hour. You are also correct that the lead time to make my money back on something like this is going to be years, not months. I also don't know what kind of maintenance you need to perform on something like this to keep it stable and running.

It is definitely more important that I have switched PDUs (* looks over at D&T) to keep rigs up than it is to keep them on when the lights go out.

I guess my main point is that your local electrician is always getting into stuff like this and will usually know of used data center equipment that is in good working condition so there is really no reason to build something like this yourself.

Should have a good update for you this evening.  The teaser is my prototype board is now switching 4 rigs  I got distracted with my sweating copper fittings on my new radiator.

I also agree about the need for UPS.  Large scale UPS isn't going to be cheap.  Even if you go the UPS circuitry for free (which is possible via salvage) just the batteries are going to be expensive.  I think I have had maybe 2 hours of power outages (likely less) in the last year combined.  Even at 20 GH/s thats what $5 in revenue.  If the UPS was free just getting 5 kVA of battery capacity would cost 100x that.  Break even in 1 century of mining time?  One would need a LOT of power outages for it to make sense and even if you did is the internet connection staying up during outages.  If not the mining farm has nowhere to submit work.

For $4K you can also buy a lot of generator back-up for your farm, at least 15kW with a 200 amp service entrance if you shop for a couple of moments, double that if you look at "functioning", or used.

Damn, I did not know there was that much juice in them car batteries. Since you seem to know a bit about this already would truck batteries be better?

Get a 48v forklift battery and rewire the cells for whatever voltage you need (it's just a conglomeration of 6v cells linked with bus bars).

Ofc, they are waaay heftier. But really what you want to look for is the $/Ah supplied, and just make sure they are capable to output 50% more than your required amperage, which is a non-issue unless the batteries are old.

It's quite easy maths really: 12V * 60Ah = 720Wh.

rjk: depends on type of batteries. And what type of battery is 6V per cell?

Sorry, my bad, not 6v. Standard lead-acid, 2.1v per cell. I don't know what I was thinking.

Just my two cents.  I have done this before for a BBS I used to run(bout 20 years ago).

You get a 1200 Pure sign(169USD) wave inverter put a good power strip to it and plug in the computer. Connect the Power inverter to 4 12 Sealed lead Acid batteries(bout 180USD). At least 20Ah batteries. Then hook a good "automatic on" computer controlled charger and plug that to the wall(must be rated for sealed or AGX batteries).  Do not use regular car batteries as they will vent fumes.  I know it works and its pretty easy. Just keep in mind you will be 10% down on efficency on the power inverter(you gain some by charger not running all the time but it is negligible). So it will cost you more that plugging into the wall. You can adjust the inverter size and battery array to higher loads also.

When in doubt, invert AC sign waves. Making it CA. It is much easier to power your farm with California power.

I'm sorry, but trolling was inevitable. Wouldn't you rather it be me than Randy?

That efficiency loss is why need to have something to switch.
HOWEVER, you could power your GPUs directly from the batteries, skipping the inverter step.
and then maybe utilizing a bunch of picoUPS: http://www.mini-box.com/picoUPS-120-12V-DC-micro-UPS-battery-backup
connected in parallel ... hmmph...

Run GPUs directly from batteries after regulators, where you have your 12V Gold/Platinum cert ATX PSUs supplying the main power, and a low voltage cutoff board, and picoPSUs supplying mobo power: http://www.mini-box.com/picoPSU-80
and splice in the loom 12V directly from battery pack, or use pci-e extenders where you splice-in from battery back, to ensure sufficient power.

Cost per system: 50$

hmmmph...

So drawing on this idea further.

Circuitry is something like:

WALL -> Trickle chargers -> Battery pack

WALL -> ATX PSUs -> Post Regulated Circuitry (Well call this power source circuitry or PSC)

Battery Pack  -> Regulators
                   -> Inverter


PSC  -> picoPSU Per motherboard
       -> GPU PCI-E connectors
       -> 12V to Mobo loom after picoPSU
       -> 12V to PCI-E extender
       -> Other 12V devices
       -> Tiny inverter for supporting 230V devices (ie. if router doesn't accept 12V, 230V Fans.)

Regulator circuitry is: Zener diode + Regulator per "lane", connecting in parallel to 2x1.5F caps.


Now tell me how friggin' dangerous is that setup :P

No PicoUPS even needed as pack is constantly being charged and 12V being supplied after the regulators. If utilizing PicoUPS then replace the regulator circuitry with them :)
ATX PSUs then connect to the bank of PicoUPS devices.

Hmmph... Time to build a proof of concept? ;D

Be sure to use some old hairdryer nvidia cards for load testing, not your expensive radeons. ;D

hahaha, was thinking ;D
I still got some half broken AGP GeForces lying around ;)
Also got plenty of prehistoric hardware for load testing :D

I guess adding several fuses, ie. 1 per card and zener diodes might be a good idea.

Has anyone enough electricity experience here and willing to tell me how to make the regulatory circuitry as efficient as possible?
and to make certain that a significant portion of the load does not come from the battery pack constantly?

Maybe utilizing picoUPS is not such a bad idea ;D

I haven't seen any that are more than 10 amps each, are you thinking of using several in parallel?

Yeap, a bunch of them.
Yes, it adds a lot of cost tho :/

Maybe one can reverse engineer from one of them and swap the components up for larger ones ;)