[SOLVED] Can I connect 2 3.3V and one 5v with ground for 12.8v?

[ZonalSilver]

I recently rewired my psu to adapt to my 14 pin mobo connector for my Lenovo mobo. I'm super tight on money and I am looking at a nice graphics card, but it requires a 6 pin power connector. I have the adapter, but I had to use the 12v wires from the molex connectors to power the mobo. I was wondering if I could connect other wires to make near 12v and connect those in place of the 12v wires on the molex connector so I can use the Graphics card I am getting.

My other question would be if I could take one of the 12v wires from my mobo and use it to power my Molex connector or if I could split one of the 12v wires to do that? Like splitting one 12v wire and sending one part into mobo and other into molex to power my GPU?

I don't have another PSU and I need to find a fix to use my GPU that I am getting, is there anything I can do to fix this?

BTW I am a decent pc tech and will understand most things, but I wanted to know if this could be done safely or provide a stable connection to my GPU

 

[kanewolf]

Most power supplies have very low amperage on the 3V and 5V supplies. You might get 12VDC but won't have enough amperage to do more than power some disks or fans...
Won't work for a graphics card. Buy a quality power supply that has PCIe BEFORE you buy a graphics card.

 

[ZonalSilver]

Most power supplies have very low amperage on the 3V and 5V supplies. You might get 12VDC but won't have enough amperage to do more than power some disks or fans...
Won't work for a graphics card. Buy a quality power supply that has PCIe BEFORE you buy a graphics card.

I just checked my PSU, I have 24A on 12v, 40A on 5v, and 32A on 3.3v

Will that be enough for a stable connection, I only have my mobo plugged into the PSU, 2 hard drives and my 40w GPu plugged into the mobo, drawing power from it. Plus 2 fans.

The PSU is a 550W, I just don't have the proper connectors for it to use, power isn't an issue with this PSU

 

[Azzyasi]

How exactly do you want to add those voltages?
You will short the psu if you try the series connection because the negative (ground) is the same for all voltages! So because of that the PSU can only give 3.3V, 5V and 12V and 7V (between 12V and 5V.. usable for slowing fans) or 8.7V (between 12V and 3.3V.. hard to do since 3.3 is present only in the 24pin and sata conectors)
You can add voltages in series only if you have distinct positive and negative (two batteries, two psu's, etc) and even with two psu (three in your case for 2x3.3V+5V) there is another serious problem on the AC part where the ground is shared and the whole case is grounded.. you would need isolation from the ground to make distinct positive and negative for each PSU.

So for your case, if you are absolutely confident that the PSU part can handle the 12V load, a new 6pin pci-e connector hooked on any 2 (better 3) yellow wires (12V) and 3 black ones from the psu will do the trick. Just take the wires from unused connectors like molex. Also you would need the actual pins and 6pin pcie connector, easily found on any adapter. or from a donor PSU.

If you have two cables with molex from the PSU (on separate cables up to the PSU) this will work https://www.amazon.co.uk/dp/B07CG59K9M/ref=psdc_407733031_t1_B008AS7660 (again if you are confident about the PSU wattage).

And by the way, what psu do you have? if it's dual-rail you must be careful to load the CPU on one rail and the GPU on the other rail.

 

[ZonalSilver]

How exactly do you want to add those voltages?
You will short the psu if you try the series connection because the negative (ground) is the same for all voltages! So because of that the PSU can only give 3.3V, 5V and 12V and 7V (between 12V and 5V.. usable for slowing fans) or 8.7V (between 12V and 3.3V.. hard to do since 3.3 is present only in the 24pin and sata conectors)
You can add voltages in series only if you have distinct positive and negative (two batteries, two psu's, etc) and even with two psu (three in your case for 2x3.3V+5V) there is another serious problem on the AC part where the ground is shared and the whole case is grounded.. you would need isolation from the ground to make distinct positive and negative for each PSU.

So for your case, if you are absolutely confident that the PSU part can handle the 12V load, a new 6pin pci-e connector hooked on any 2 (better 3) yellow wires (12V) and 3 black ones from the psu will do the trick. Just take the wires from unused connectors like molex. Also you would need the actual pins and 6pin pcie connector, easily found on any adapter. or from a donor PSU.

If you have two cables with molex from the PSU (on separate cables up to the PSU) this will work https://www.amazon.co.uk/dp/B07CG59K9M/ref=psdc_407733031_t1_B008AS7660 (again if you are confident about the PSU wattage).

And by the way, what psu do you have? if it's dual-rail you must be careful to load the CPU on one rail and the GPU on the other rail.

I have that part you listed from Amazon, which is what I am trying to use.

I want to connect like 2 3.3v and a 5v wire into one wire, then use that wire as my 12v, even though it would be 11.6v. Then proceed to use the molex connector's as the GPU's power.

I am basically trying to replace my 12v wire with others, and trying to add them up to make more.

So like if you add 2 AA batteries, you get 3v instead of 1.5v. Can I add several positive wires with 1 ground wire?

 

[ZonalSilver]

And I just found out, no. You cannot do what I was trying to do. It causes a short and forces your PSU to shut off. So I will have to find something else to do on my GPU

Thanks anyways guys

 

[Azzyasi]

I have that part you listed from Amazon, which is what I am trying to use.

I want to connect like 2 3.3v and a 5v wire into one wire, then use that wire as my 12v, even though it would be 11.6v. Then proceed to use the molex connector's as the GPU's power.

I am basically trying to replace my 12v wire with others, and trying to add them up to make more.

So like if you add 2 AA batteries, you get 3v instead of 1.5v. Can I add several positive wires with 1 ground wire?

NO YOU CAN'T ADD THOSE VOLTAGES!

The reason is the shared ground. You have the black wire in the psu that is common for all voltages. So to add voltages in series you need minus-plus-minus-plus-minus-plus and the ends will have the total voltage. Works fine for batteries since each have their own minus refference of potential. A PSU will have the same minus, so imagine all the minuses shorted by a wire. Clearly you will short circuit the psu on those voltages. As stated before in theory could work with separate psus where you get need to hook 5v from psu1 to ground of psu2, hook 3.3v from psu2 to ground of psu3 and finally hook your load between ground of PSU1 and +3.3V of PSU3. This is just theory since there is another danger of shared ground of the mains (the cases are all connected by the grounding in the mains outlet) that adds another level of complication. Even unearthed, the cases of each psu should never meet eachother since they are likely different potential.

In short: NO YOU CAN'T