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I recently acquired some interesting server PSUs, and have been wondering whether I could put them to use. The problem is that they produce 48VDC, not 12VDC like most of us are used to. The even larger problem is that they are MASSIVE. Here are the specs:

18KW total (Yes, 18,000 watts) per enclosure, with each enclosure holding six actual hot-pluggable PSUs. The enclosure is divided into two banks of three PSUs, rated for 2950 watts each at 51.7 VDC.
200-240 VAC autoranging input at 50/60 HZ.
3 phase (aprox 75 amps total at 240 VAC)

Here, have a pic:

https://i.imgur.com/2JwMCl.jpg (https://i.imgur.com/2JwMC.jpg)

Wonder if a 48VDC to 12VDC PSU could maintain high efficiency and be useable to power mining rigs.
P.S., I already asked about this on an RC airplanes forum, but the max they can use is something like 32VDC and I can't find an appropriate buck converter anywhere. My next place to ask will be on an electric-car website....

A bucking converter of that size would probably end up costing you far more than what you paid for that server psu assuming you didn't pay all that much for it. (and I don't know where you'd get one) You'd probably be better off just selling that thing and buying some standard 12v power supplies.

Yeah that's what I figured. My next thought was to find out whether each rig could get a small converter, instead of having one huge one. So each rig would have its own PSU still, but the input would be 48VDC not 120VAC. Anyone know where I can get such things?

+1 i don't know what this is, but it looks awesome! 8)

are these from a SUN Sunfire based on ultraSPARC processors? I know SUN sold converters at one time...

Loving that ginormous gauge wires, Kokjo? Miner-porn right there.

No, its a power supply for HP/Compaq blade servers. Usually two such PSUs per rack, and three blade enclosures per PSU (six total).

Interesting but I agree it would be very costly to get 48VDC to 12VDC done right even w/ 1 per rig.

Now if you found a 6KW high efficiency 12VDC supply at a good price well that would be like finding a diamond.
I would run one baby supply for each rig and all the video cards powered by that monster.

Have a look into equipment for solar cell / off grid living. Some of those systems are 48VDC and such. They may have some converters for bring 48 or 72 V down to 12V. Probably still pricey though.

I had the same idea and found this. Quite cheap, 100 bucks for 2.1kw

https://www.google.com/search?q=Dell+NC003+power+supply&hl=en&safe=off&client=firefox-a&hs=I91&rls=org.mozilla:en-US:official&prmd=imvns&source=univ&tbm=shop&tbo=u&sa=X&ei=_wYsT4KxGtHJmAWqyInqDw&ved=0CEYQrQQ&biw=1366&bih=675

It is an used dell blade server PSU, rated 2100w with 12 volt 175A max. I don't know how many rails it has.

http://www.txcesssurplus.com/catalog/14299-dell-NC003-psu-label.jpg

Also not sure about its efficiency. And how to start this little monster is the problem. It has some kind of control board for hot plugging function, not just a dumb PSU

Oo look 12 volts!
I'll bet the RCGroups forum goers would be all over that. They aren't too worried about efficiency, they just want to charge their airplane batteries faster. ;D

Check out http://vicorpower.com/cms/home/product-selector?productCategory_filter=DC-DC%20Converters (http://vicorpower.com/cms/home/product-selector?productCategory_filter=DC-DC%20Converters).

Vicor DC/DC converters go up to 750W, and you could use multiple ones.

I have tons of Vicor AC/DC power supplies with 12V output and plan to use them for mining purposes later this year.

Those look cool, but lookit what I just found:

http://www.ebay.com/itm/290580661302

2700 watts, 91% efficiency, 220VAC input. The problem is that there is little to no info on specific specs, efficiency curves, pinouts, etc for these PSUs - can't seem to find them. Perhaps someone knows where to find this info from Dell? That is a PSU from a current-gen M1000e blade enclosure.

OK, I ended up getting a couple PSUs - the 2100 watt ancient old one, and a current-generation 2360 watt PSU. Links:

http://www.ebay.com/itm/360429090503
http://www.ebay.com/itm/320841281011

Some of both still available.

Also, for the 48v PSU at the start of the thread, I googled for hours and hours, and finally came up with a spec sheet - with pinouts! - located here:
http://www.powerconversion.com/support/document-search.php?document=datasheets/bulk/hps3kw.pdf&crc=a82414ca74abd2804175d11a6dcef3be3a5422a2

I need to find a multimeter and start poking around.

You might get away with a DC-DC Step up transformer to go from 48->120 or I suppose you could find a DC-DC Step down from 48-12.  I thinking the step down would be easier to source although a std PSU outputs 12v, 5.5V, and 3.3V which is going to either a) limit its uses or b) cause wiring headaches.  If you could find a 48-120 Step Up that might be the easiest bet.  What's the efficiency of that thing?  Methinks you're going to lose a lot of power to heat with something like this.

rjk i use this meter for a lot of things it works great
http://www.harborfreight.com/5-in-1-digital-multimeter-98674.html

I just found that these suckers can be linked in parallel. Jeez. 2x 18kw = 36KW, or 750 amps at 48 v.

The cool thing is, the little paralleling link is just 4 small wires to balance the power outputs between 2 racks. Wonder if I can attach a pot or something to tweek the voltage. I already opened the enclosure, and it should be trivial to convert it from 3-phase to single phase at 240VAC.

The conversion to 12v is not going to be worth it at these power levels - the better thing to do would be to see if I can get the power outputs down from 51.7 VDC to 50.4 VDC, and use it to charge 14 cell LiPo batteries. They would probably charge in like 2 minutes lol.

LiPo batteries have a max charge rate of a few C.  Charging them faster can damage them and lead to catastrophic failure.  The absolute fastest you're going to charge any LiPo battery is about 15 minutes at 4C charge rate.

Enigma

I sincerely hope you're not being serious. You are aware that lithium-* batteries require (http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries) strict current and voltage levels (http://www.powerstream.com/UPS-Battery.htm)?
You can't just throw more voltage/current at them to make the recharge faster - the protection circuit board won't allow that.
Circumventing the protection unit is a surefire way for a magnificent fireshow.

Nah, not had any experience with it, and probably won't bother. Will do a bit of research though, looks like something interesting to learn about. According to the spec sheet I found, the PSUs have +/- 5% voltage adjustment built in.

Sure you can, I charge lipo at more than a few C all the time.  Protection board, lol.  Like any large format lithium battery has an integrated BMS. 

Sounds like your thinking about laptop batteries.

Most non-consumer lithium ion/lithium polymer cells do not have a built in protection circuit, and they WILL take a charge at MANY C - This degrades the cell though.  In some cases, pretty seriously..

If you haven't witnessed the actual failure of a Lithium cell, consider yourself lucky.  They often fail in a spectacular way.