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10v From 2 Usb Ports?


telot
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I'm a far cry from an electrical engineer, but I do work with 12v systems (solar/batts) on a daily basis. We wire 6V batteries in a series to get 12V. For an example of the concept, see this picture:

http://www.otherpower.com/images/series_wiring_diag.jpg

I'm wondering if I can do this same thing with USB power. I run my wifipineapple, which requires 5V, from a hacked USB cable no problem. Heres my deal, I have a 9-30V cellular router at my disposal that I'd like to use with my wifi pineapple in a mobile setup, completely contained with no power supply needed other than from the laptop. I have two USB ports available on the laptop - can I wire two hacked USB cables in series to produce 10V's reliably and without hurting the laptop? I'm 95% sure it'll be fine, but I just don't want to fry 2 out of the 3 USB ports...any EE's or CE's out there that can assure me I'll be just fine? Thanks very much!

telot

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I wouldn't take a chance on the return going back to one of the ports when its meant to go out power, now you are connecting to outputs together, my thoughts are you would see some sparks if you end up with positive touching a positive. Not sure how you ground something like that since its built into the cables and housing. I was reading somewhere that you could use a "bridge rectifier" if that is even a real term, to take two usb power outputs into the rectifire which would merge and make the 10v for you. Don't quote me on that, I read it on the "internet" so its "internet fact" but might not be real facts. Basically a distributer cap like in a car, but for electronics.

Edited by digip
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Connecting the +5V to the -5V on a USB port creates a short in the circuit of the motherboard and the power supply.

Thats what my fear was, that you would see sparks, or just a quick pop and then kills everything. They make special USB cables for devices that can use two ports for power, but not sure how they are made. I have one for an external HDD. I just don't think its giving the HDD 10v though. Just more sustained power and two channels for faster i/o.

Edited by digip
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I believe those usb cables for HDDs are for increasing the current, not the voltage. I could absolutely be wrong of course...Must seek out CE...

Thanks for the input guys!

telot

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I believe those usb cables for HDDs are for increasing the current, not the voltage. I could absolutely be wrong of course...Must seek out CE...

Thanks for the input guys!

telot

Correct sir. On motherboards that support above the specified 500mA of power on USB 2.0 ports the second USB connector is often not necessary. USB 3 has a higher power specification (can't remember what it is).

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