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Hey everyone I am new here and new to working on electronics. With that being said I am trying to figure out if wireing 2 of the 12v wires with 18 amps would give me 24 volts with 36 amps? I am trying to use a computer power supply to run a vape mod that is designed to run at 8.4 volts and 30 amps. I just need to figure out this part so I know what resistors I need to get and calculate the wattage. Thanks for any help! I am really looking forward to trying to get this to work

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    \$\begingroup\$ Welcome to EE.SE. This question has been asked before, many times. The answer is NO. The reason is that all PC supplies have a common ground pour and an IC to watch for under/over voltage and current. They usually have a PFC supply of 300V to 340V DC to feed the main supply, and it will burn you-not just shock you. I have spare PC supplies myself and will make buck or boost converters to get what I want. I leave the power supply as it was built. \$\endgroup\$ – user105652 Apr 12 '18 at 5:07
  • \$\begingroup\$ Thanks. I will look into the boost. I have only cut the 12 v wires and hooked them to the vape curcit board. It turns on but says battery is to high. At least this way I know what I need to start looking at. \$\endgroup\$ – Timothy Bradley Apr 12 '18 at 5:15
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    \$\begingroup\$ Even if they had separate grounds you can double the voltage or the current, but not both. \$\endgroup\$ – Oldfart Apr 12 '18 at 5:41
  • \$\begingroup\$ I just need to double the current and reduce the voltage. I just got to figure out how to do that and I should be good \$\endgroup\$ – Timothy Bradley Apr 12 '18 at 6:52
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    \$\begingroup\$ I don't believe for one minute that your vape requires 8.4 volts and 30 amps - that's 252 watts of heat an inch or two from your face. It's gonna hurt. \$\endgroup\$ – Finbarr Apr 12 '18 at 12:03
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[Would] wireing 2 of the 12v wires with 18 amps would give me 24 volts with 36 amps?

No. It would give you 12V at 18A.

The multiple 12V wires on an ATX power supply are all connected together at the PSU end -- they're intended to be used together, as a single wire of that size would probably overheat if it carried the full output current itself. The ratings on the power supply are its overall capacity, not the capacity of a single wire.

I just need to figure out this part so I know what resistors I need to get and calculate the wattage.

That isn't going to work. First, resistive power dividers can only drop voltage, and even then can only do so consistently with a constant load, not with a dynamic load like your vaporiser. Second, dropping from 12V to 8.4V at 18A is 64W -- you'd be putting out a dangerous amount of heat in your voltage divider. The sizes of resistors you're probably familiar with are rated for 1/8 or 1/4 W.

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  • \$\begingroup\$ I am ordering bigger resistors to handle the wattage and also looking into a DC to DC adjustable voltage regulator. If that would help it. If it does I need to find a way to increase the watts and amps after the step down to 8.4 v \$\endgroup\$ – Timothy Bradley Apr 12 '18 at 7:42
  • \$\begingroup\$ Again, you are going about this the wrong way. \$\endgroup\$ – StainlessSteelRat Apr 12 '18 at 12:51

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