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Two power supplies in parallel

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April 16, 2011 3:18:54 AM

I am thinking about adding new video board to my computer, a power hog of a video card and I know the present PS in the computer won't be able to carry the load. I have other PS's, none with enough power to power the load. Here's my question: could I add the second PS, both are for ATX motherboards, by doing a lot of cutting wires and soldering, so that both PS's would be connected to the motherboard, in parallel. I realize that the real answer would be to buy a more powerfull PS, but it would't physicaly fit in the space that the present (low power) PS. Would it be like connecting two battery's in parallel (no problem) or would the two PS's "fight" to maintain their voltage "set points"?
April 16, 2011 4:57:53 AM

It's rarely worth doing, especially since you get into crossload situations on the secondary PSU that put the voltage out of spec. Don't be cheap, it's not worth it.
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April 16, 2011 6:59:25 AM

It's not so much a matter of money, I just can't fit a higher powered PSM into the computer. Thanks for the reply.
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a b ) Power supply
April 16, 2011 7:53:14 AM

Then my friend, sell your PC and put the acquired funds towards a pc that will meet your requirements.
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a b ) Power supply
April 16, 2011 10:10:57 AM

Buy a new PSU to support whatever load you need.
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April 16, 2011 11:49:45 AM

Your just going to blow up your computer.. just find a psu that will fit or get a new case since its not a matter of money.
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a c 243 ) Power supply
April 16, 2011 3:01:21 PM

jsc said:
Using two inexpensive PSU's is not recommended, but ...

Using two cheap PSU's:
http://www.tomshardware.co.uk/forum/279908-12-motherboa...

Scary thread but
Therion_97 said:
the first psu had 20 pin atx cable, the second has 24-pin, and that 4 pin could separate and connect on the 4-pin slot which was left empty because first psu only had 20-pins, that way when i power up the pc both power supplys started to work

There's no way the secondary psu would start just by hooking up the 4 pin, unless the proper pins on the main connectors were jumped, and then feeding the MB from 2 completely different source's was no-no right off the bat.
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April 17, 2011 2:55:43 AM

Thanks for all who replied to my post. Thought it might be a bad idea, but now I know. Thanks again.
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a b ) Power supply
April 17, 2011 3:55:01 AM

To more directly answer your question
Your question " Would it be like connecting two batterys in parallel (no problem)"
Ans: No it is not the same, You can connect two batteries in Parallel as long as they have the same voltage (ie 12.6 volts for car Batterys. When you do this, if one battery is low say 12.2 volts, the 12.6 volt battery will charge the first and Eout will be equal. The current during this time is Very high. You NEVER paralell electronic PSs and it is for this same reason, if the voltage for one is slighlty >< the other, then one PS will either be a load or a source to the other psu. Almost similar to putting two AA batterys (1 a Nicad 1.25 V, and the Other a normal 1.55V) in parallel - end up with two bad batteries.

Can you use two PSUs in the same compute? Ans Yes. But you must insure that the circuits are isolated from one another. Ex. PSU1 +12 V to all Molex and PS2 to all pcI-e +12 V connectors = OK. Psu1 4 pin atx conector to !/2 of 8 Pin atx mb connector, Psu2 4 pin atx power to other half or if you have a GPU with 2 PCIe connectors and you connect PSU1 to one and PSU2 to the other= no-no.
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