5W/5V Panel to Charge a 5V USB Power Bank?

Discussion in 'The Projects Forum' started by mystic, Sep 21, 2016.

  1. mystic

    Thread Starter New Member

    Sep 6, 2016
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    Would it be possible to have a 5V/5W solar panel charge a USB power bank (5V/1A USB power bank) using a module like this? My load is powered by USB, which would be directly connected to the USB power bank.

    My concern is that a solar panel, as I understand it, only gets to 5V when it is in very bright and ideal conditions. If it is not, the voltage will drop below 5 V and therefore it would be unable to charge the power bank. In addition, the module that I linked to accepts 5V and not less than 5V.

    Should I just try to find a buck-up module that can accept lower voltages and force the panel voltage to match 5V (or higher if that's better)?
     
  2. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    Does your power bank require a 12V input to its charger?
    According to the legend on the underside of that module it accepts between 3V and 6.5V
     
  3. mystic

    Thread Starter New Member

    Sep 6, 2016
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    USB power bank is straight USB-to-USB charging, which according to the USB specification's is 5V.

    I just saw that as well (3-6.5V). Then I would assume it should work then even if it the solar panel voltage drops below 5V.

    I read somewhere before that step-up modules are "not as useful/technically efficient" as step-down modules. But for these small voltages it shouldn't be a problem.
     
  4. #12

    Expert

    Nov 30, 2010
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    Your main problem is with the solar panel. The sunlight that hits the panel is not going to be constant. The best you can do is use a diode to make sure the current doesn't back up through the solar panel when the sunlight is bad.

    Here are some good Shottky diodes at 25 cents to 40 cents:
    http://www.mouser.com/Semiconductor...Z1yuobnnZ1yuoc7hZ1yuo73fZ1z0y4ci&Ns=Pricing|0
     
  5. mystic

    Thread Starter New Member

    Sep 6, 2016
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    Wouldn't the solar controller do this already? That is one of the functions (to prevent current backup).
     
  6. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    Which solar controller is this that just appeared?
     
  7. mystic

    Thread Starter New Member

    Sep 6, 2016
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    Sorry that I didn't mention this. Something like this.
     
  8. #12

    Expert

    Nov 30, 2010
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    You want to use a controller that only works with 5V and up (excess voltage) to fix a problem about a lack of enough voltage? That doesn't make sense.
     
  9. mystic

    Thread Starter New Member

    Sep 6, 2016
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    0
    My mistake. It looks like this controller doesn't accept lower voltages than 5V, just as you said.

    In such a case, it would be easier (and cheaper) just to use a diode like you mentioned. Would you be able to give me advice on how to choose the appropriate diode? The page you linked has over 10 pages.
     
  10. AlbertHall

    Well-Known Member

    Jun 4, 2014
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  11. #12

    Expert

    Nov 30, 2010
    16,247
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    That's right. Ten pages of diodes that are very generous in their specifications...hundreds that will work...none that won't work...for prices as low as 25 cents. You can print out all ten pages, throw a dart at them from 10 paces, and hit a diode that will work. What kind of help do you want?
     
  12. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,879
    371
    Interesting component selection technique, there.
     
    #12 likes this.
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