combining power supplies

[Freakazo v2.1]

I have a 500W power supply and a 350W one, I would like to combine the two (maybe hold a little ceremony for their *marriage* ).

I have a 8800GT and will get a amd phenom 9750, so I want to get the most power to both of them. and bragging rights that I have 2 PSU's Dude!

The GFX card supply is simple, it has one of those 6pin connectors and I have a 2 molex connector to 6 pin connector so that easy.

But the supply for the CPU is kinda a problem, I want to combine the 2 mobo connectors. I have experience in some basic experience in electronics and got al the tools, so that isn't a issue (soldering wires together and using heat shrink tubing etc.)

I know that (for example) the 3.3V wires has a tolerance of 10%, so if one psu gives out 3.27 and the other 3.33 and I combine them, 1will there be any current that goes from the higher voltage one to the other wire (other psu)?2 will it be destructive to the other power supply?

My logic says that there will be current flowing threw, perhaps I'm wrong?
3.are there any other problems I haven't thought about?

I building my own custom case from scratch so space is definitely not a problem.

 

[killadoob]

there is no way to do this as far as i know apart from jump starting the one power supply everytime u bootup

doing it the way you want to could end up with alot of dead hardware

 

[The_Unbeliever]

You can look at buying a server case which can take two PSU's at a time and which you can swap out if one fails

A bit expensive, but worth it if you want to have it

 

[SilverNodashi]

I won't recommend this, especially not on the CPU. Mind you, the CPU is probably cheaper to replace than your VGA card

What EXACTLY do you want to achieve? Do you need more power? Then rather get a 1KW PSU Do you need redundancy? Well, your mobo, CPU, RAM, VGA will be your first point of failure then, not your PSU.

Or do you just want to combine then cause you have them? Take advice, don't pop something just cause you can

 

[howardb]

I already have 2 PSU's linked for simultaneous boot from motherboard - I used this guide to make my custom cable.

I made the harness myself from the steps in the link about 4 years ago. All the bits and pieces needed are available either from a local PC shop, hardware store or from eBay (got my ATX PSU extenders from there). Just remember to read the instructions thoroughly and check twice before actually cutting/plugging-in anything - you can't go wrong. Oh, and don't rush it - let the silicone dry properly...

In those last four years, I've had no problems at all with the dual-PSU cable, and my PC is running on 24/7 (with the occasional reboot after an XP update). Not too sure about using the latest PSU's as they are getting a bit complex, but my two z-450W aOpens are great... getting a couple of 700's soon...

Here are my PC specs, with pictures if wanted...

Be very carefull with the newer PSU's...

 

[killadoob]

u want 1.4kw to run a 7800gs?

makes no sense at all

both those power suppliers should run even a 9 series vga card

 

[Freakazo v2.1]

1:I won't recommend this, especially not on the CPU. Mind you, the CPU is probably cheaper to replace than your VGA card

What EXACTLY do you want to achieve? Do you need more power? Then rather get a 1KW PSU Do you need redundancy? Well, your mobo, CPU, RAM, VGA will be your first point of failure then, not your PSU.

Or do you just want to combine then cause you have them? Take advice, don't pop something just cause you can

Why don't you recommend it?

I want more power. Especially for future proofing it when I want to go to the sli route (dual 8800gt's and maybe tri later on )

I overclock so I calculated that I will need more power when running 2 8800gt's and when I get the phenom cpu

u want 1.4kw to run a 7800gs?

makes no sense at all

both those power suppliers should run even a 9 series vga card

There is no such thing as enough power

there is no way to do this as far as i know apart from jump starting the one power supply every time u bootup

doing it the way you want to could end up with alot of dead hardware

I will solder each wire to the corresponding wire on the other cable, thus when the power up signal is sent it will be sent to both the power supplies.

and I want both of the power supplies to give power to the cpu so that method of the combination of power supllies won't work for me since that way I will have one power supply to power other things like cdroms etc. I want it for the cpu.

 

[stefan9]

Here's a modding guide on how to do this. http://www.pcformat.co.za/modules.php?name=Forums&file=viewtopic&t=28649

I am not a modder so I take no responsibility for the end results of doing this.

 

[Brawler]

u want 1.4kw to run a 7800gs?

makes no sense at all

both those power suppliers should run even a 9 series vga card

maybe because of this?
3.5TB of HDD storage (2 Int. WD 500GB SATA, 6 Int. WD 250GB SATA, 2 Int. WD 250GB PATA, 2 Ext. Hitachi PATA 250GB

 

[BiteMe]

and I want both of the power supplies to give power to the cpu so that method of the combination of power supllies won't work for me since that way I will have one power supply to power other things like cdroms etc. I want it for the cpu.

why do you think you need both psu's for the cpu?

p.p.s. doing it your way will mean you are tying both grounds of the psu's together, i just wanna put my hand up now and let you know this is an instant recipe for causing k@k

voltage is actually potential difference, and this will vary for one psu to another, the potential difference is "as measured from ground" and the two psu's will have "ground" at slightly different values.

but pay more attention to my cpu question, i really am curious why you think this way

 

[bekdik]

Which voltages are supplying the greatest current? If, for insatance, the 5V supply is being overloaded, then I cannot see any advantage in separating the 12V supply, you would need to add a higher power 5V psu.

Maybe someone who understands electricity can explain.

 

[Freakazo v2.1]

if you have a 5v that can supply 5A and another psu wich can supply 2A and you combine them you will have a 7A supply (max A draw). My multimeter is flat now, so I can't check if there's a difference between GND and GND.

I would think that all voltages (in PSU's) are measured against earth (actual ground)

 

[bekdik]

if you have a 5v that can supply 5A and another psu wich can supply 2A and you combine them you will have a 7A supply (max A draw). My multimeter is flat now, so I can't check if there's a difference between GND and GND.

I would think that all voltages (in PSU's) are measured against earth (actual ground)

The link given by howardb above shows that 5V is supplied by one psu and 12v by the other psu.

I'm not sure that simply connecting the 2 psu in parallel would provide the sum of their respective ratings. Firstly the actual voltage relative to a common ground will differ as the supplies are not run by a common regulator. Next the internal impedance of the two psu's are different, so I would expect a current to flow from one to the other and I doubt that a psu is designed to sink a current source.

I suspect that the smoke following the flash will be a kind of milky blue bordering on black.

But I'm probably wrong.

 

[HavocXphere]

Soldering them together in parallel is not going to fly. What you could probably do is run some components off the one PSU and the mobo of the other. e.g. fans and drives of one and mobo connectors off the other.

To be honest the entire thing doesn't sound like a very inspired plan.

 

[bekdik]

got my hands on 2 250W power supply's, will just use jumper wires and connect each one together short the green and will record a video of the exact colour of the smoke

A true scientist

Suggest you put a piece of 5A fuse wire in series with each of the plus sides before you join them. You may limit some of the damage.

 

[Big Kriss]

Guys,If anything the two psu grounds need to be a reference to both psu`s.You cannot have the two separate and floating.You need a common ground or earth.
Two supplies rated at two different current(amps) outputs do not matter.
The voltage is the sticky one here..A supply will deliver ONLY what the device drawing current from it needs.So there is no "un balance" regarding the current in two supplies..
If the current draw exceeds the first psu output delivery the second psu can be relied upon to make up for the shortage though...this is after all the reason that we went with 2 psu`s in the first place.
The two most important criteria here are the volts that must be same and the common earth or ground as reference to both psu`s.

Another reference to this.
http://www.overclock.net/power-supplies/14455-multiple-power-supply-guide.html

 

[Freakazo v2.1]

Perhaps the easiest route would be to just use #1 psu gnd. The #2 would just give power to the other pins. I have 30something zener diodes (breakdown voltage of +5.6V and 13.~5V) so if there is any small leakage current they should stop it. But if the test of tomorrow goes wrong (smokes) I'll buy higher watt diodes.

There aren't really any articles about doing what I want done out there sadly

 

[kronoSX]

thats better,do that freakazo

 

[Freakazo v2.1]

The voltage difference between the 2 psu ground is 7.3V and that seems to be the global difference (3.3 5 and 12V).

Now I got a question, yes another one.
Will I be able to power my HDD from the two separate power supplies?

 

[sn3rd]

Well the best would be to think it through, take all the measurements you need, and then simulate it over and over again to make sure it does what you expect.