Using a split USB cable for extra power?

MarioJP

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Sep 2, 2009
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I've have heard of this before, and actually gone and bought one of these cable off ebay. It is a female to dual usb male cable basically. I want to be able to link 2 USB mobile packs for combined charging power. Will this work at all? Anything I should be aware of by doing this, Any cons pros?

Thanks.
 

LEDAdd1ct

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Hudson Valley
I can't comment on your specific application but I own a cable which can pull power
from two USB ports at once for my USB wifi radio.

It is supposed to prevent overloading one USB port.
 

MarioJP

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Sep 2, 2009
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The application for this is able to charge mobile devices. I want to increase charging effiency. Using a single mobile pack as it is just drains the internal cells before the device ever gets to 100 percent. I am guessing these mobile packs has a boost/regulator circuit to maintain 5v for USB charging. If I link 2 of these same USB packs together solve this problem?
 

MarioJP

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I forgot to mention that the usb charger runs off AA's. Using eneloops.
 

hiuintahs

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I've have heard of this before, and actually gone and bought one of these cable off ebay. It is a female to dual usb male cable basically. I want to be able to link 2 USB mobile packs for combined charging power. Will this work at all? Anything I should be aware of by doing this, Any cons pros?

Thanks.
It would work but you would need to isolate the outputs of the 2 USB mobile packs with p-channel mosfets configured in a "diode-or" configuration. Schottky diodes would also work but you'd lose power with the voltage drop across them. You wouldn't want to have one output fight the other output if they are regulated outputs. It's probably more hassle than it's worth and thus a bigger battery pack makes more sense. Also another thing to be aware of is the gauge of your USB cables. I prefer a minimum of 24awg gauge when drawing power. Most of the cheap data cables are 28awg for both data and power.
 

MarioJP

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Sep 2, 2009
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That is what I am discovering. I notice one usb charger would keep charging the device while the second one act as if nothing is plugged in which is causing balancing problems. Their voltage readings of the first and second pack cells are way off. The 4 cells on the first pack reads around 1.28v, and the second pack which are 4 cells reads 1.41v. So yea I am not liking where this is going. My theory was I thought the circuit inside these units would take care of this.
 
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