# 15v from 20pin and/or 24pin ATX Power Supply. Connecting PSU circuits in series

I have a portable 12v car battery charger, jumper, maintainer, and inverter with integrated USB ports, 12v car adapter slot, jumper clamps, emergency LED light, and a 3 prong 110v/60hz wall outlet. It is charged by a 15vDC input using a common cylindrical DC plug. I have a male connection that fits and is capable of supporting the current drawn by the unit. I however do not have an AC/DC conversion box for 15v.

I have USB ports but I have heard that you CANNOT chain USBs in series. I also have several desktop PSUs with 20/24 pin ATX, 6 pin PCIe, 4 pin IDE, 2 pin CPU, and SATA connections.

My question is, using the available connections, can +15v DC be achieved? If USB can be used in series, how? If not, can I use the PSUs?

I have 4 units to work with, one being 20 pin and 3 being 24 pin. I think Ihave 2 possible options using the PSUs. Wire 5v in series to get 15v. Would 3 PSUs be needed? I dont fully understand how the circuits connect internally. Would this simply be a matter of: GND|+5v -> GND|+10v -> GND|15v?

Alternatively I could use 9 sources of 3.3v in series to make 29.7v. I could then halve the voltage to make 14.85v. I am still unsure of the internal workings of a PSU, furthermore i do not know how to divide the voltage of a DV circuit. (probably my next google search)

I can also acquire if needed 19.5v and 9v adapters

Please forgive me for any errors. I would be happy to correct any issues in this post. I mean only to improve upon available content and enrich the community.

• To connect two power supplies in series, they must be isolated from each other. The power rails provided by an ATX PSU are not isolated. Dec 30, 2020 at 14:22
• @Hearth If i understand you correctly, your saying that since the ground is a shared connection for the entire unit, a series connection would all use the same ground and effectively result in a parallel connection. Dec 30, 2020 at 15:36
• No, a series connection would use all the same ground and result in a short circuit. Dec 30, 2020 at 15:36
• @Hearth I may have failed to clearly state: I have 4 separate PSUs. Would the use of separate units result in the necessary isolation to achieve a series connection? and would the psu be able to handle the increased voltage? EDIT: So the use of the same ground by 2 voltage sources connects the 2 sources together aswell, that being the problem correct? Dec 30, 2020 at 15:39
• The 0V output of an ATX PSU is, I believe, referenced to mains earth, so they still aren't isolated enough for this purpose. Dec 30, 2020 at 15:41