making a 9 volt battery charger

Discussion in 'The Projects Forum' started by gvfc2, Jun 28, 2011.

  1. gvfc2

    Thread Starter New Member

    Sep 14, 2010
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    I'm trying to see if a usb wall charger will charge a 9 volt battery and be able to charge a phone while its not plugged in to the wall. What I mean is when its plugged in it charges the 9v. When it isn't plugged in it charges the phone.I have a european usb charger I took apart and going to make it usable with us sockets. The circuit board number is 908-55 and it is from courier charger model #TJ-8908<ic>. Please help me
     
  2. Audioguru

    New Member

    Dec 20, 2007
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    896
    What chemistry is the 9V rechargeable battery? Ni-Cad or Ni-MH?
    Some are actually only 7.2V (six cells) and others are actually 8.4V (seven cells).

    USB is only 5.0V so it will not charge a 9V battery.
     
  3. wayneh

    Expert

    Sep 9, 2010
    12,127
    3,048
    And a typical 9v battery has many fewer amp-hours than you'll need to charge a modern cellphone battery.
     
  4. gvfc2

    Thread Starter New Member

    Sep 14, 2010
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    The 9v is nimh. What I was thinking was before the it goes to the usb have it branch off somewhere to have a charger for the battery which then will be connected to the usb to charge the phone at a flick of the switch. Forgot to add I already have a battery powered usb charger that's the simple thing that steps it down to 5v and max amp is 1amp. And I've kind of charged my phone. Its more like an extra battery. But I do have another one of those chips left over if I would need to use it
     
  5. Audioguru

    New Member

    Dec 20, 2007
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    What is the mAh rating of the little 9V battery and what is the mAh rating of the battery in the phone?
    The little 9V battery has much less capacity so it will not charge the phone much.
     
  6. gvfc2

    Thread Starter New Member

    Sep 14, 2010
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    The 9v is 200mah. The battery in the phone I don't really know. Ill have to take another look
     
  7. gvfc2

    Thread Starter New Member

    Sep 14, 2010
    11
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    The phones battery is 1500mah. I could get 2 9v batteries. The charger puts out enough to charge the phone with 2 batterys so all I need right now is a charging circuit for the 2 9v batteries. I should be able to figure out the rest
     
  8. Audioguru

    New Member

    Dec 20, 2007
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    The phone needs 1500mAh.
    One 9V battery is only 200mAh.
    Then you need 7.5 9V batteries to fully charge a dead phone battery only one time.
    You also need a 5V regulator to reduce the 7.2V to 8.4V from the 9V batteries to 5.0V.

    You need a charger IC to charge 9V Ni-MH batteries.
     
  9. iONic

    AAC Fanatic!

    Nov 16, 2007
    1,420
    68
    Thats a lot of investment to charge a cell phone battery, more than if you just purchase a second cell phone battery, and you won't have to wait hours to use your phone again.
     
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