USB 3.2 milliamps output?

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OK, so I'm modding a cooling tray with 2 140mm 12v fans, I'm going to use a voltage stepper to get the 12v, I read usb has a MA output of 500ma, the fans I'm using draw about 120ma. General rule of thumb is upping voltage drops the amps. I'm not familiar with the exact science or potential loses, or even if the MOBO would allow a little more juice.

Some dude on youtube did the same thing, but claimed the output at 12v with the stepper from a usb 3.2 still gave around 350ma. Does anyone know if this is true? I mean he shows the fans and connections and they work perfectly. as long as it's safe I don't mind, tbh if they end up running slower I can always just use a 2.1a quick charger to power it as they usually only draw what they need rather than what's on offer. Could also then add another fan for good measure too lol.

Edit: Just found this:

"
The original USB 1.0 spec (and the updated 1.1) allowed devices to draw up to 500mA from the port. USB operates at 5V, so that means a maximum of 2.5 watts.

USB 2.0 has the same power limit. But later there were add-ons to the spec for battery charging, allowing up to 1.5A (7.5W) while data transfer is going on, and up to 5A if not. Few USB 2.0 devices can deliver that much power. Also note that the Micro USB connector is only rated to carry 2.1A (10.5W), so that’s the maximum charge rate for a phone that uses 5V charging.

USB 3.0 increases the power limit to 900mA (4.5W). The battery charging spec from USB 2.0 can optionally be supported."

Is that accurate, cause if it is that kinda answers my question.
 
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When you change the voltage the power remains the same. There is conversion loss though which depends on the circuit you use. So if you have 2.5W in you have 2.5W out minus the conversion loss. So if he is gettting 4.2W out it stands to reason that he is probably putting about 5W in, so he must be running in the order of 1A out of that USB. I mean I am not sure of the losses, that's my guess, but if you look at the documentation for the converter it should tell you.
 
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@pp111 Converter hasn't arrived yet and there wasn't much detail in the listing. I have messaged the seller though.
USB 3.2 is a usual of 900ma, so as long as the losses aren't ridiculous, I imagine I should be able to run 2 fans quite easily. Famous last words and all...
 
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The usb power outpoot will depend from motherboard to motherbard
If you pull that amperage the 5V will become 4.7V and it will draw more amps so the problem becomes compounded
Do you have to run the fans at 100% ?
If you give them 10V they will draw less amps
And that will allow you to use 1 port
 
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