Wire Dual Power Supplies together to One Motherboard

I’ve been building a custom acrylic case for my pc and my current power supply isn’t cutting it will all the hardware that will be going into it. I’ve got two 350W PSU’s that I want to hookup to my one motherboard. How do I go about doing this?

And please no suggestions on getting a beefier PSU as I have already dremelled out the hole for the second supply :slight_smile:

These links may be helpful…




Hey thanks a lot, the last link was the easiest to follow. Got my two PSU’s up and running now! :slight_smile:

Some pictures would be nice :wink:

Wish granted. Sorry for the shakiness, was going fast. Please note I am also not done building the case so this is a work in progress. I started this acrylic case project about 2 weeks ago. It has room fro 8 optical drives and 6 hard drives (after I build the drivecage). I still need to cut the hole in the front add fans and lights etc. And add the other side panel. Then I will be done. I am also moving the yellow case out afterwards. It is just supporting the watercooler right now. The 2nd PSU is hard to see, but it’s beneath the motherboard.

I guess this can help those who have two lesser powered or two older power supplies, and avoid buying an expensive new one.

I myself an opting to try it on my b*tch machine!!!

I also think it’s a great tip for most people. I’ve known it for years but haven’t ever tried on my PSU myself. I was just not sure where to find the right wire. :slight_smile:

There are 300-watt PSU products with prices like US$5 or even lower. I have no idea whether wiring two of them will make it better than US$10 300-watt PSU. :slight_smile:

If you hook up the second unit via a 12V relay switch you can have the secondery unit power up when you turn your system on. I can’t remember where I got the how-to from but I’ll find it if you want to try this…

Both of mine do turn on when I boot the system, the second one runs my hard drives and water cooler right now.

Which method is that using ?. Did I see a method that combines the power of two PSU’s ?.

The third link is what I used, and the both turn on with the booting the pc.

WARNING connecting two power supplies together may cause serious damage to the power supplies and the equipment that they are connected to.

The master/slave setups illustrated in this thread should be okay. But, connecting two power supplies so that their regulated voltages are connected to each other, is BAD.

Background) Most power supplies use one circuit to power one transformer to make all of the various output voltages. Then, one output voltage (usually the +5Vdc) feeds back to tell the input side of the transformer what to do. The other output voltages are controlled by their relationship to the feedback voltage. (They come off the same transformer using different windings) [very over-simplified] So, the input side of the power supply regulates itself to make the regulated voltage come out right; and the other voltages drift according to what is happening to the regulated voltage.

Problem) If the two different power supply regulated voltages are connected to each other, they will make the power supplies unstable.

Lets say PSU 1 regulates it’s +5 line to +5.015 volts. Let’s say PSU 2 regulates it’s +5 line to +5.013 volts. If the two regulated voltages are spliced together, PSU 1 will pull all the load off PSU 2 by pushing the +5V to +5.015 vdc. It’s other voltages (+12V, -5 V, -12V and +3.3V) will go high. PSU 2 will reduce it’s output to bring the +5V down to +5.013 vdc. PSU 2’s other voltages will also go low. The motherboard and other devices will be caught in the middle of the conflict.

Real power supply sharing systems use extra circuits to prevent PSU 1 from affecting PSU 2 and vice versa.

So, link 3 is bad. Don’t do it. Your hardware will thank you.

Two power supplies that do not connect to each other (other than to turn on the slave PSU) are okay.

yuknow, I’ve been thinking about trying this ever since I read the post. I bought a couple of cheep psus from ebay and today have been prepairing to try to splice them together to make a psu for a nice new machine that I’m building. However there was this nagging doubt that it might not be such a good idea so I thought I’d visit here and see how that guy’s getting on who did the mod. Luckily for me you got here ‘sweetums’, with what sounds very much like good advice, and I can see that my worries were right.
You mentioned that this might be possible with the addition of a seporate circut though, do you know how, exactly ?.

I’ve tried to find out how multiple power supplies are isolated for a long time, but I have not found out how the pro’s do it. I work on similar power supplies every day, but my employer’s products are not made to be paralleled. I think it is kind of a trade secret thing.

I worked for one manufacturer who made his schematic diagrams hard to read on purpose AND copyrighted the screwy schematics to prevent people from duplicating his products. There are no real secrets in electronics.

If you can take something apart, then you can probably determine enough to duplicate it. But the cost of documenting how it is put together is usually enough to keep people from stealing “your” design.

…when you say that you have not found out how ‘the pros’ prepair their units so that they can be used in parralel. Who are we talking about here when you say ‘pros’ ? Also I don’t understand what you are trying to say in the last scentance of your post at all, what are you saying ?
Number .o08888|88880o.

Running the two psu’s independently of each other like I am, is ok. Trying to combine their power would be dumb. The only splicing is for 1: to allow the 2nd psu to operate without being attached to the motherboard, and 2: to have it boot up when you press the power button. I’ve been running the two psu’s together like this nearly 24/7 since this thread was created. It’s perfectly safe.

…this can be acheived by just grounding the power good and switching this unit on before boot. There isn’t any connecting of wires needed. :rolleyes:

No its not neccessary, unless you want to flip the power switch manually at boot up.

I think I have got a bit confused because in the third link, that you say you have used, it states;
"What if you could wire two 300’s together and make a 600 watt PS? "
and it goes on to explain how to, supposedly, do this.
I got confused by this as the wording seems to suggest that it is a how-to that will enable a person to make a combined watt power unit from two units, rather than a ‘how-to’ with instruction on how to add a slave power unit to your machine that can be used for farming out to your drives/cooling system/cathode lights.
Hopefully you can see why I might have made this mistake…
8 :slight_smile:

When I say pro’s, I mean the server grade hot-swap power supply manufacturers. ETASIS, 3Y and Delta.

When I was talking about stealing designs, I was explaining why it may be so hard to find info about paralleling “switched mode power supplies”, one of the popular generic names for this type of power conversion device.

It is almost impossible to design electronic assemblies that cannot be duplicated and relabeled. If electronics designer-manufacturer “A” designs a hot-swap power supply system that works and becomes popular; then then manufacturer “B” could make it cheaper and sell it for a profit, if he knew how.

Fortunately, for designer-manufacturer “A”; most manufacturers are too cheap, and profit margins are usually so small, to buy something, take it apart and reverse engineer their own product.

There may be reference material on how switched mode power supply paralleling circuits work, but I have not Googled it out yet. The only info that I remember finding is that there is a diode network based passive design and an active design. I have not seen anything beyond that.

End of Parallel SMPS design info search

Master-Slave setups should be fine. There should be no problems as long as “ground” is the only shared output. Problems cannot happen long as both power supplies are NOT directly connected to the same device.

IDE, and SCSI, cable connections between the drives and the motherboard, or controller card, should be okay for standard devices. Neither standard uses a direct power buss connection in the connector cables. (except ground, and I checked SATA too)

BUT, connecting one power supply to the motherboard ATX power connector AND connecting the OTHER power supply to the motherboard’s secondary connector is probably a BAD thing. Unless you have a motherboard that was designed (like some server mobo’s) to use two power supplies. By secondary I mean the ATX 12V connector or hard drive style connector that some mobo makers add to help people with old fashioned non-ATX12V power supplies.

So long, bye, I have enuff other things to do, I am gone until next time.