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Dual power supply - does it work well
- Thread starter tomana
- Start date
Yes, more like 14A.
I just added a second PSU in with relay wired to the first PSU, I can post pictures if anyone likes.
It works well, resumes from sleep correctly. One PSU runs the motherboard and Video card. The second PSU runs all my fans, drives, and provides power to my 4870 over one of those old converters that takes two Molex's (drawn from seperate strings) and converts to one PCIe power connector.
I was having stability problems before, I think because my PSU was simply getting up in years. It's rock solid now in prime95 where it crashed before after just a few minutes, and I had some extra juice to add some more cooling fans in. Total price:
$0 - The second PSU was a freebie from an old Dell I got for free, 300 Watt ATX.
$2 - Relay from Radioshack
$0 - Extra wires from old broken stuff
$1 - Crimp connectors (because I'm lazy)
Simple Howto: http://www.directron.com/2powersupplies.html
$3 for boosting my PSU capacity by at least 250 watts. Not the most energy efficient solution, however.
EDIT: Actually might be pretty energy efficient, since I'm not using a newly manufactured PSU, saving energy used for transport and manufacture.
It works well, resumes from sleep correctly. One PSU runs the motherboard and Video card. The second PSU runs all my fans, drives, and provides power to my 4870 over one of those old converters that takes two Molex's (drawn from seperate strings) and converts to one PCIe power connector.
I was having stability problems before, I think because my PSU was simply getting up in years. It's rock solid now in prime95 where it crashed before after just a few minutes, and I had some extra juice to add some more cooling fans in. Total price:
$0 - The second PSU was a freebie from an old Dell I got for free, 300 Watt ATX.
$2 - Relay from Radioshack
$0 - Extra wires from old broken stuff
$1 - Crimp connectors (because I'm lazy)
Simple Howto: http://www.directron.com/2powersupplies.html
$3 for boosting my PSU capacity by at least 250 watts. Not the most energy efficient solution, however.
EDIT: Actually might be pretty energy efficient, since I'm not using a newly manufactured PSU, saving energy used for transport and manufacture.
Last edited:
Good point, but the voltage provided to the PCI-e supplemental connectors are standard, I do believe. So make sure the motherboard is being powered entirely by one PSU, but if you like you can power the GPU on the second PSU. Someone correct me if I'm wrong.
For kicks, I tried running this old Dell on a dual PSU setup using the adapter I'd built with both PSUs powering the motherboard, one doing the 20pin connector and PSU2 doing the extra 4 pin motherboard conector. The computer ran fine, but the second PSU never turned off(!), so all the fans and drives it was connected to just kept going even with the computer off. Also all the lights on the computer remained on when the computer was "off." So, yeah... that's probably not good.
Yes, obviously the PCI-E connectors use standard voltages. But that has nothing to do with using a second PSU.
Well, it does mean you can provide power to the GPU using a second power supply while powering the Mobo with PSU #1. That's pretty significant because the GPU is a big power draw. In one pop you can take off 100 watts of load from your primary PSU, no need to rewire all the fans and re-do cable routing like I did.
Up tonight. Take apart PSU #1 (the PSU seated in the normal PSU spot, where the SPDT (the rectangular one) power switch is accessible from the outside). Take the two leads from after the SPDT switch (or after the relay it runs to, if that's the case) and run that onto some low gauge (thick) wire. That wire then runs to the plug on the internal PSU (PSU #2). Now there's only one PSU to plug in and it's power switch also controls the second PSU.
Potential problem would be forgetting about the second PSU when moving from 120V to 220V country, and failing to change the voltage input switch on it. Solution: Only use auto-switching PSU for PSU #2.
I'll post some pics of this mod tonight after I do it since it is a bit more interesting. In class now.
that would be a problem with PSU #1 as well....unless you like fireworks.
Well, you really ought to be using a quality PSU with APFC so you don't have to deal with that problem altogether. A single good PSU is always a lot better than two crappy ones.
Yeah, but that one is visible so you'd ought to be able to remember that switch.
Agreed, if you're doing a new build. But since I already had a high quality Seasonic supplying all the expensive components (Mobo, CPU, Video card), there's no need to replace that when I all I need to power are fans and drives.
Done, now a single power switch controls both PSUs.
In this picture you see a wire splice on the internal AC line in the primary PSU (warranty already expired anyway)
The whole thing working!
Basically, the primary PSU has a power cord comming out of it with a PSU style plug on the other end. The second PSU is internally unmodified. You can see it suspended in the top of the case (behind the green cord).
One mistake I made at first, the relay needs to be connected to ground (black) and 12v (yellow) on the primary PSU. Then on the green and black on the secondary PSU. That way the relay is active when the 12v line is live. Obvious, but I managed to mix it up when not thinking what I was doing.
In this picture you see a wire splice on the internal AC line in the primary PSU (warranty already expired anyway)
The whole thing working!
Basically, the primary PSU has a power cord comming out of it with a PSU style plug on the other end. The second PSU is internally unmodified. You can see it suspended in the top of the case (behind the green cord).
One mistake I made at first, the relay needs to be connected to ground (black) and 12v (yellow) on the primary PSU. Then on the green and black on the secondary PSU. That way the relay is active when the 12v line is live. Obvious, but I managed to mix it up when not thinking what I was doing.
You should consider adding a diode across the relay, the inductive spike on turn-off could potentially be harmful to anything else attached to that particular psu's 12v rail.
As you already know, if the secondary psu encounters a fault it will shut down while the primary continues to run...not sure how that would turn out with suddenly unpowered gfx cards in a running system.
As you already know, if the secondary psu encounters a fault it will shut down while the primary continues to run...not sure how that would turn out with suddenly unpowered gfx cards in a running system.
- Joined
- Apr 7, 2006
- Messages
- 10,477
Why not just use something like this?
http://www.frozencpu.com/products/5637/cpa-167/Lian_Li_Dual_Power_Supply_Adapter_Cable.html
http://www.frozencpu.com/products/5637/cpa-167/Lian_Li_Dual_Power_Supply_Adapter_Cable.html
There's a bunch of little VRMs on the video card that handle any power conversion and stabilization needed. They actually are some of the major heat generators on that thing. Have to be careful with 3rd party heatsinks as some don't cool them well enough. The stock heatsink does fine.
Power comes via the PCIe slot, and the PCIe connectors. A PCIe slot is actually spec'd for quite a bit, in the realm of 75 watts, but companies are generally conservative and knock on external power before that point.
Power comes via the PCIe slot, and the PCIe connectors. A PCIe slot is actually spec'd for quite a bit, in the realm of 75 watts, but companies are generally conservative and knock on external power before that point.