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Connecting USB outlets in parallel for more current draw?

Discussion in 'General Electronics Discussion' started by seanspotatobusiness, Dec 13, 2014.

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  1. seanspotatobusiness

    seanspotatobusiness

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    Sep 11, 2012
    I want to use a lithium battery pack for a project. This one lets you draw up to 2.4 A, 2 A and 1 A from the different outlets. I would like to know whether I'd have any problem taking the power from each and connecting them in parallel so I could draw a maximum of 5.4 A (I'll avoid approaching the maximum).
     
  2. Anon_LG

    Anon_LG

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    117
    Jun 24, 2014
    There is not really enough information on the project to come to a conclusion, I would not recommend it. Why do you need to draw 5.4A? That is a lot of power, tell us what your project involves, unless it's an electric heater. The battery bank contains a lithium ion battery, they ARE NOT to be messed around with, they are very dangerous is misused. Describe your project and you can receive further help.
     
  3. seanspotatobusiness

    seanspotatobusiness

    193
    4
    Sep 11, 2012
    Yes, it's an electric heater (specifically in an item of clothing I'm making). The heating elements will be lengths of enamelled wire in the arms, legs and torso. The lengths will be calculated and measured to ensure current draw is not excessive.
     
  4. Arouse1973

    Arouse1973 Adam

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    1,087
    Dec 18, 2013
    A couple of points from me, but not knowing how these units work I am only surmising. If the outputs are current limited and not constant current you may run into problems.

    This is because if any of the individual outputs differ in voltage for some reason then you might find one output feeding back into the others, this could be eliminated by using diodes.But this wastes power and produces a system volt drop which may not be desirable.

    If feedback of current does happens it may damage the unit. Also if the demand on the 2 Amp port goes beyond what it is rated for then this will go into current limit. If the system uses fold-back limiting then the output could oscillate.

    The other point is the USB cable is not rated for such high current, so don't think about using a splitter and then running into one cable.

    The designer of the system may not of thought of this because it wasn't designed to work this way so they may not have any safety provisions in place. I haven't seen this done so I might be wrong .
    Adam
     
    Last edited: Dec 13, 2014
  5. Bluejets

    Bluejets

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    Oct 5, 2014
    Enamelled wire will esentially just be a dead short.
     
  6. BobK

    BobK

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    Jan 5, 2010
    Really, for any length?

    (100m of 30ga is 33.9 Ohms, not what I would call a "dead short")

    Bob
     
  7. Bluejets

    Bluejets

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    Oct 5, 2014
    Well then I guess the wearer will become an induction heated. o_O

    To be fair, there was no mention of any particular guage wire and in any case, not suitable as a "heater".

    Nichrome ..???

    and 5V/33.9R = 147mA = 0.7W
     
    Last edited: Dec 13, 2014
    davenn likes this.
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