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Power Bank phone charger

  1. Sep 10, 2016 #1
    Hello,
    I have built a portable power bank to charger my phone when necessary.
    But I have a problem with it. When I charger the power bank, it is charging only my battery pack which is NiMh, it is not charging my phone at the same time.Therefore, I wanna ask ,how I can make my system , so it charges my phone and battery when it is plugged to power supply.When the batteries in pack are full, they are charging my phone. So please let me know your opinions.The schematics is given in pic. IMG_20160910_111657.jpg
     
  2. jcsd
  3. Sep 10, 2016 #2

    davenn

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    I see a problem in the middle section ... do you see it ?


    Dave
     
  4. Sep 10, 2016 #3
    Nope I dont see it. Could you be more specific?
     
  5. Sep 10, 2016 #4

    davenn

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    5V and 2.5V on the same line ???????
     
  6. Sep 10, 2016 #5
    yes, the buck converter outputs 5v and it is connected to battery.Two battery gives out 2.5 volts.So when I measured the middle point, it showed 2.5v. What can we do about it?
     
  7. Sep 10, 2016 #6

    Bandit127

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    It looks to me like you are charging the NiMH batteries with 5V. I wouldn't...
     
  8. Sep 10, 2016 #7
    Yes I am charging with 5v .Why would not you do that?
     
  9. Sep 10, 2016 #8

    davenn

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    you shouldn't have 5V and 2.5V coming together at that point

    cuz you are likely to cook them
    there should be a separate line to a correct charger circuit for the NiMH's. The NiMH output voltage total should be 5V and then a separate switching circuit to switch between the 1st 5V supply and the battery pack before going to the phone the second 2.5 to 5V converter isn't needed
     
    Last edited: Sep 11, 2016
  10. Sep 11, 2016 #9
    What if I lower the 5v to 2.5v as the battery pack voltage and step it up to 5 v?
     
  11. Sep 11, 2016 #10

    davenn

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    that's a bit pointless cuz as I said in my last post you don't need the second converter, just a waste of space and resources
    increase your battery pack capacity to 5V is a much wiser move. I really don't see the point of a 2.5V battery pack
     
  12. Sep 13, 2016 #11

    CWatters

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    Read up on the charging requirements for NiMH cells before going any further.

    You aren't really meant to charge them from a constant voltage source. They should really be charged by a constant current source. Any kind of medium/fast charging also needs charge control (eg circuits to stop over charging when the battery is full). Overcharging a NiMH cell can sometimes cause them to overheat. That can cause the heat shrink insulation around the cell to split leading to short circuits and fire. Been there, done that.

    Sometimes it's easier, cheaper and safer to just to buy one.
     
  13. Sep 14, 2016 #12
    The way its wired now the buck converter is probably pushing too much current into the NiMH pack causing an overload. The buck converter goes into current limiting mode and that's why voltage drops to 2.5V. So you're using the boost converter because the buck converter is overloaded. That's a crazy thing to do. There should be a charging circuit on the 12V line for the NiMH pack and only the buck converter to power the phone.
     
  14. Sep 17, 2016 #13
    https://e.mail.ru/attachment/14741015700000000579/0;1 I added couple of batteries to make battery pack 4.8 v. But still it is not charging my phone. I even tried to charge my phone from a buck converter which outputs 5 v and connected to power supply. My phone was only getting 0.1A .But when I connect only battery pack it was sucking 0.6A .Why phone is taking only 0.1 A?
     
    Last edited: Sep 17, 2016
  15. Sep 17, 2016 #14
    This is the way I connected my phone and buck converter. Still cannot understand, why my phone is taking only 0.1 A.Please let me know your feedback. IMG_20160917_113911.jpg
     
  16. Sep 17, 2016 #15

    CWatters

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  17. Sep 17, 2016 #16

    davenn

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