SMPS related query, is this a right place?

[vawtwindy]

Dear members, its been long time for now, seriously, i was away from RE after building a 12V wind turbine based on Hugh book, and using the same for 3 months (without wind now it is just turning around as show piece), so added 250Watts X 4 solar panel to charge my batteries (3kva UPS 600Ah batteries) . Basically i use them for running my computers @ home (24/7).

Recent days i planned another ATX based compute,r AMD 42xx series processor(115Watts), 16GB ram(, 1TB single Hard drive, 10/100/1000 LAn, without additional devices. But one thought came in mind, how about connecting this machine to a direct DC instead of AC->DC converting SMPS(mostly i need to use 550Watts to 750Watts if it is AC->DC smps), for this i need to have regulated 3.3VDC, 5VDC and 12VDC. One way i am thinking is having rectifiers to deliver 12/5/3.3 VDC power, but how long can i use rectifiers?

Other ways are can i feed  DC power to SMPS itself? eliminating the transformers and connecting direct battery power? what are all the pro's and con's? if i have to do this what are the methods i need to start with? any documents, links?

Now the windy season starts here, on an average i will get 4.5m/s to 7m/s, so planning to add another 24 V wind mill, apart from this increasing the capacity of batteries is also in plan.

-VW

[mab]

certainly it is better to go direct from battery dc to load dc using a SMPS; I made a small convertor to drop the 24v from my battery to 19v for the laptop, but if you want 3.3/5/12/-5/-12 for a desktop, then you will need a more sophisticated SMPS.

an ATX psu should work from 240v dc as they rectify the ac anyway; I'm not so sure about 120 dc, as the ATX psu's I've modded use voltage doubling when set to 120v to charge the caps up to 340v dc.

Not sure I understand what you're saying about rectifiers

[Mary B]

DC to DC convertor is what you need.

[OperaHouse]

I do that sort of stuff all the time, but that is something I would consider not worth doing.  I would want some electrical isolation between the battery and the computer.  As said earlier, many of these supplies work fine on 240-340 DC.  I buy broken inverters.  Many of these have shorted FET in H bridge output.  Many of these I don't even repairing.  I just bring the DC out and run CFL, DVD, TV, etc on 140DC.

[vawtwindy]

thanks for your input dear mab, mary alana and OperaHouse

mab i am using only 24 V battery bank, as you and maryalana suggested let me start hunting for DC to DC converter stepup circuits. mab please ignore about the rectifier part as i was thinking. Opera House can you share few pictures pls? or some sort of circuit diagram.

Personal friend has shared link about google servers which is having DC battery connected along with the servers,  (Concept of laptop?) which is pretty impressive.  Let me scan google search engine for more knowledge on the same.

http://i.i.com.com/cnwk.1d/i/bto/20090401/GoogleServerLarge.jpg
http://asset3.cbsistatic.com/cnwk.1d/i/bto/20090401/Google_data_centers-1.jpg

--vw

[vawtwindy]

Google doc shows

We believe this energy-saving power supply technology can be applied to home computers, too. So we've been working with Intel and other partners to propose a
new power supply standard. The opportunity for savings is immense — we estimate that if deployed in 100 million PCs running for an average of eight hours per
day, this new standard would save 40 billion kilowatt-hours over three years,  or more than $5 billion at California's energy rates.

http://www.youtube.com/watch?v=xgRWURIxgbU

Please refer the attached image for std PSU vs modified google psu

[OperaHouse]

Nice pictures but NOTHING technical. You will be saving maybe 20% with single conversion which is nothing. Just hacking a bunch of power supplies together will probably use more power.

[vawtwindy]

Not able to trace more technical details on the Google PSU, but now they say 90% (as of 2009) usage, but normal PSU's are capable of using 50% to 60% only, Every single computer migrates to this kind of PSU might yield enourmous amount of saving's.

I referred this doc  http://www.flowdas.com/o/files/2009/10/PSU_white_paper.pdf

today i am planning to open a 450W standard PSU (might cost 8 to 10 USD).

[OperaHouse]

Maybe you should get your info from BING!  I read that white paper, Thought I was reading USA TODAY.  That is really stretching the facts.  Those extra voltages don't really take up extra power though removing them would allow extra copper in the transformer and extra space could eliminate a fan.  Cost saved from removed parts could be put to a more efficient design.  They cherry picked numbers to be dramatic.  Most supplies probably do better than 70%.  When it comes to supplies you will be fed a lot of carefully crafted lies. I was working with a KIS supply and looked up the smps chip.  They proudly state 94% eff but back in the lit it drops to 70% under certain conditions.  This is a sync rect.  Never would have believed it could drop that low.  Just about every China module states 97%.  Good luck with that.  Anyway the PC is dead and don't need to worry about that.  550-750W.....Are we talking about a toaster?  That will be fun finding a module that will do that.  CPU board better be a throwaway.  Things happen.

[Mary B]

Most SMPS are 85+% efficient with many over 90. That is the main draw of them is much higher efficiency and less heat.

[vawtwindy]

, OperaHouse,  pls refer this http://www.amazon.co.uk/550W-Gold-Silent-Power-Supply/dp/B000KND4M8, mary i do agree with dear OperaHouse, i feel most of the PSU's deliver max of 70%.

[Mary B]

That would be a very poorly designed SMPS at that efficiency level, it isn't that hard to optimize the magnetics for 90+% efficiency. I have done it on a 2kv ham radio supply that was home built.

[mab]

trouble is they're optimised for low cost, not efficiency; for e.g. they use schotkeys for the 5v & 3.3v (high current) outputs but at those voltages the only efficient option is syncronous rectification (which is easy, but costs a couple $ more).

[OperaHouse]

There are no power supply police.  I have a 600W Xantrex that will put out 5V @ 89A.  Those computer power supplies don't look anything like that inside.  Have you ever measured how much power the computer actually uses?  I haven't built a PC in a long time.  I suspect the numbers could be pretty low.  For that reason I can't garner any interest in this project.   I have a couple Vicor 28V DC converters that put out 5V at 20A.  9 inches of wire would make two of them share current pretty well.  Those qould cost you about $60 each on ebay.  12V would be a couple of 2596 converters.  A lot of expense for not much savings in power I suspect.