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Power Bank Improvement

Discussion in 'General Electronics Discussion' started by spencer_manzon, Dec 31, 2014.

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  1. spencer_manzon


    Jan 8, 2011
    Hello everybody,

    I have a project that aims to improve one of my power banks.
    Here is the progress of my project:

    IMG_20141231_004550 (Small).jpg

    Since the original PCB (the blue one) of the power bank only puts out 4.3V (which is out of spec for usb charging), I salvaged a PCB (the green one) from a USB charger powered by 2x AA batteries which puts out a nice 4.9-5.1 volt output.

    Now, this is where things get complicated.
    1.) I wanted to connect the new charger PCB (the green one) to the old charger PCB (the blue one) via USB (there were two ports, I removed one port). Since the bloody blue PCB could not supply the current needed by the green PCB (which is 500-600mA, tested with a USB Doctor (blue box)) because the blue PCB could only output about 250mA on its "2.1A port", I set off for Plan #2.
    2.) Now, I noticed that I could turn on and off the LED flashlight on the blue PCB. I could wire up the green PCB on that one (added bonus of an ON/OFF switch) but I am uncertain of the current that the LED driver could put out. So, I set off for Plan #3.
    3.) Plan #3 is where I am troubled. I am choosing to keep the bloody blue PCB for its charging capabilities for the battery pack but I am torn in wiring the green PCB. I was almost gonna wire it directly to the battery pack (the battery pack is in parallel and are li-ion cells) but I was worried for the cut-off voltage for the pack. I am assuming the cut-off circuitry is in the blue PCB because it shuts off when the battery is used up. Will it be safe to wire it up or do I need to buy one of these: ? By the way, the IC in the green board is a TD8228 which draws voltage as low as 2V.

    Thanks for reading my long post. Cheers! :woot:
  2. 73cat


    Dec 30, 2014
    It's look like good one, I will try to build 1 for my self..
    You are great men.
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