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Homemade battery power bank safe?

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  • 21-06-2015 9:31am
    #1
    dencal
    Registered Users Posts: 7 ✭


    My micro-usb port on my phone is no longer functioning. So instead of buying a new phone or waiting weeks for a cheap battery power bank to come in from China (stuck for cash), I was thinking of making my own.

    I have this Anker multi-port charger here:

    amazon.com/dp/B00VH8ZW02/?tag=stackoverfl08-20

    I noticed it is certified safe, but I'm not entirely sure what this implies:

    "Certified Safe: Anker's MultiProtect safety system ensures complete protection for you and your devices. Worldwide 100-240 volt AC input voltage."

    Now, if I was to plug a usb cable into this power source, snip it, and connect the appropriate wires to their respective +/- connections on the battery, will it charge up safely?

    Assuming I don't let the cables touch, and I do everything right etc.

    I saw this done on the internet but saw a comment saying that the battery will over-charge which is not healthy for the battery.

    But I was thinking maybe this Anker "intelligent" multi-port power source would eliminate this problem.

    What do you think? Thanks for any answers!

    (Really don't want to have to buy a new phone or battery bank)
    Tagged:


Comments

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    #2
    corglass
    Registered Users Posts: 1,113 ✭✭✭corglass


    Long story short, it won't work. You're missing the charging circuit when you directly connect a power supply to the battery. The charging circuit monitors the battery voltage and regulates the delivery current accordingly to safely and correctly charge the battery.

    Any direct connection may not (will not) be at the correct voltage and will delivery incorrect current profile, possibly blowing up battery if it doesn't have short circuit /thermal overload protection.


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    #3
    spideog7
    Registered Users Posts: 1,230 ✭✭✭spideog7


    No that will damage the battery and very likely cause it to explode (lithium cells burn violently).

    I don't see how "a cheap battery power bank" will work for you either, since they all use the USB port.

    What type of phone do you have? Is there a chance it has a built in wireless charger?


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    #4
    mawk
    Registered Users Posts: 2,738 ✭✭✭mawk


    Yeah you can. Ish.
    I do this kinda thing pretty frequently.
    A bench power supply is a big help though so you can see the current an voltage in real time and also limit the current.

    Imagine a battery like a water balloon and the power supply like a tap. If you over fill the balloon or use too high a pressure it will burst. But with lithium it's dramatic..

    I'd take an old Nokia charger or similar (3.7v whereas new USB ones are 5v) as it will be harder to explode the battery. Cut the head off that. Check polarity with a meter and note the correct wires and pads. +to+ - to -

    Then put the meter in current mode and put it in series with the charger wire. Press to the battery and look at the meter. If you're drawing over about 150ma I'd find a resistor to lower the input voltage until the battery doesn't take so much current.

    Charge slow and frequently check the temperature. When the voltage of the supply and the battery gets closer the current draw will slow.
    Don't leave it unattended. I did once and coated my kitchen with boiling paste from an overcharged nicad pack. Lithium would have been a fire.


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