Dual PSU power cost?

Jerahya · Sep 7, 2017

Basically I just realize my 500 watts PSU can't handle the whole system that I made the whole time that's why it freezes or shuts down without a warning. So I have a 750 watts PSU generic that I'm going to use on a PC and the 500 watts is going to power the GPU. Will the cost of my bill increase base on the both PSU running or it will consume just the same amount like I'm using a single PSU? It would be getting a better PSU but that would be next month so I'm going for an alternative? Anyone enlighten me?

Kasper Jorgensen · Sep 7, 2017

This is not something you should do. Don't mix 2 PSU on same system unless the whole system is designed to make use of more than 1 PSU.
Get a larger PSU and not some generic crap, get a proper quality one.

Jerahya · Sep 7, 2017

Kasper Jorgensen :

I do know that risk and doing so will either kill the GPU or the PC depending on who dies first. Its not my main rig so no biggie if it happens. I just want to know if using 2 PSU does increase my bill while I still have no decent PSU power it.

Kasper Jorgensen · Sep 7, 2017

No it will not use more than your computer use plus the wasted watts depending on efficiency.
Still I hope you know what you are doing, worst case can set your house on fire.

Jerahya · Sep 7, 2017

Kasper Jorgensen :

don't worry I've done this many times already just like what I did to my fist gaming PC. I'm just not sure about the bill wise. I never heard of anyone burning their system with this unless they connect 2 different PSU on the same GPU. It may kill GPU but that only happen at certain factor like powering the PSU for the GPU without powering the PC.

Kasper Jorgensen · Sep 7, 2017

The thing is that GPU is not only powered by the 6 or 8 pin connector, but also by the motherboard through the pcie slot. 75watts can be drawn through the pcie slot.

Jerahya · Sep 7, 2017

Kasper Jorgensen :

Took note of that. And the system will tell right away that it is running into some problems like voltage of one PSU drops and the other keeping a high one causing malfunctions and probably shut down or turn display off then kill the GPU without putting everything on fire or if I'm lucky it just throws a bluescreen telling me that it just won't work. Its an Emtek GPU anyways so no biggie if it dies.

cryoburner · Sep 7, 2017

What are your system's complete hardware specs? Most likely, one of those PSUs would offer plenty of power for the entire system, unless you're running multiple graphics cards (or the PSUs have major issues).

As for the cost, PSUs will only draw as much power as they need, so a 500 watt PSU powering 100 watts of equipment will only use 100 watts of power (plus another 10-20% that gets lost in the conversion process)

Kasper Jorgensen · Sep 7, 2017

Yeah didn't think of that, why not just use the 750w to power the whole system.

Jerahya · Sep 8, 2017

Kasper Jorgensen :

It doesn't have the 6 pins for the GPU plus it will probably be supplying 40-50% of the power.
Whole system works though. I just won't abuse it that much and limit the time that the kids uses it until PSU is replaced.

Gam3r01 · Sep 8, 2017

If it has zero PCIe cables then it likely is not a true 750w unit, its probably more in the range of 450w.
Not only is using two PSUs independently a bad idea (IF you ever had a reason to run two, there is a proper way to link them together), but you are also doubling the number of cheap units in the system.

I wouldnt do it.

Jerahya · Sep 8, 2017

Gam3r01 :

Anyways I did a bit more troubleshooting on the 500W PSU that I was actually using on the system before it started giving me problems. all 12V, 5V and 3.3V are perfectly fine except for the -12 which is just giving -11.27 V below 10% minimum tolerance. Where do you usually ask for help regarding fixing this type of hardware your self. I really want to go cheap on a system that I'm not going to use.

Kasper Jorgensen · Sep 8, 2017

There is probably nothing to fix. That is just how it is with cheap units. Nothing you can do about it other than getting a better quality unit.

TJ Hooker · Sep 8, 2017

Jerahya :

-12V is still within spec, and -12V rail is barely used (if at all) in modern PCs AFAIK. What are you using to measure voltage? Are you reading the voltage at low/no load? If so, that doesn't really tell you much.

Jerahya · Sep 9, 2017

TJ Hooker :

but doing a quick read 10% is the minimum tolerance for -12V which means it should be -11.8V is the acceptable voltage that the PC would run. Although all of the other PSU I have working that I also tested are also below the minimum tolerance of about -11.5V to 11.7V. Its just this one that the PC refuses to boot. When using the PSU will -11.27V PC turns on but no post no display. Although when Putting that PSU in the case it seams to ground the whole case reason for me to get a bit shocked on it. Maybe the PSU is shorting out somewhere since it works perfectly fine when using as a secondary PSU for the GPU. I connected both SPU to a single AVR so it anything fails AVR should shut the whole thing down. I hope. I'm using multimeter tester to measure each pins.

Kasper Jorgensen · Sep 9, 2017

It's a cheap unit and when used as only PSU you are stressing it to the limits and when that happens on cheap units all kind of things can happen because they lack all the basic protections.

Jerahya · Sep 9, 2017

Kasper Jorgensen :

if its something to spend on I wouldn't bother reusing some of the old stuffs I have. I didn't have to pay anything for it since its all used parts that I have from my old PCs I keep except for some games. If it works it works. My niece actually spent 2 hrs playing on it and so far it keeps on going.

TJ Hooker · Sep 9, 2017

@Jerahya err, you may want to check your math. -12 with +- 10% tolerance corresponds to -13.2 to -10.8 V. So again, your PSU is within spec. And again, if you're measuring voltage with little to no load, it's not going to tell you anything. To verify your PSU is performing properly you'd need to see if the rails are staying within spec at max (or close to max) load. Which isn't necessarily easy to do yourself.

turkey3_scratch · Sep 9, 2017

You still never listed your specs. Additionally, some more description on your problems could be helpful. So sometimes it freezes and other times it shuts down? When it shuts down does it turn back on? When it freezes what happens?

If I recall the -12V rail is absolutely never used in any modern day PCs, so it has zero relevance. Most PSUs don't even have -12V circuitry anymore if I recall, it's rare to even see a PSU with one, though if you have some old one it might.

Jerahya · Sep 9, 2017

turkey3_scratch :

Ow, I though no one cares what it was build out of.

Trust me it is an old build when I say an old one.
Its running a Q9300 quad core
4GB of ram
GTX 560
motherboard is old G41 so it will use the -12V rail I just don't know how much though.
and that't pretty much how low end the PC. Tried the PSU even on my actual gaming rig or my dad's PC it all turns on but no display, no beep. I wonder what causes it to no boot the PC.

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