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What to do if Xiaomi Mi Power Bank 2S suddenly does not charge phone nor itself and the only indication is a faint battery level and LED flickering? This may be answer.
A kid complained about his USB power bank refusing to charge his phone nor itself. Upon connecting the cable and pressing the button the power bank responded with a faint random battery level LED flickering. There wasn’t any rattling inside nor noticeable physical damage. I wondered If the battery was too discharged. The only option left was disassembling the unit to see what happened.
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Mi power bank disassembling required a semi-soft and flat prying tool for back plate removal and Phillips #0 and Phillips #000 size screwdrivers. You can use a metal spudger to slide in the internal frame if needed. iFixit Essential Electronics Toolkit includes all of the essential tools.
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The nut driver in the photo isn’t usually required. I used it to press the bent aluminium case corner back into shape when the internals were pulled out.
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The top and bottom covers are fastened with double sided tape. Insert prying tool near the middle of the bottom cover where the model name is shown. Slide it around cover to loosen the tape.
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Remove the two screws at each corner with the Philips #0 screwdriver.
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Turn power bank with sockets to bottom direction. Slide and pull the internal frame out. If the internal frame is stuck, press several times in the middle of the case and along the case length. Jimmy knife or metal spudger can be used carefully to free the front side plate from outer case.
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The charge controller circuit board is fastened to the frame with two small screws and two pins at the sides. Remove the screws with the Philips #000 screwdriver. Carefully press fixing pins to release the board.
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Battery is glued to frame with weak glue. Use prying tool or spudger to loosen the battery from the frame.
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Remove the bent battery terminal metal piece from the controller board battery pad. If removal of the bent piece is not possible, then flatten the bend. Drop a solder blob over the pad.
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Put solder on end of battery terminal strip. Keep temperature between 250..270C degrees.
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Solder battery terminal to controller board pad.
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Assemble power bank back in reverse order. Install controller plate and battery back in frame.
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Insert the assembled internal frame into the outer case. Screw it back down with the two #0 screws. Set the cover back into place.
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Xiaomi Mi Power Bank 2S appeared easy for basic repairs. Glued parts are easy to remove and they stick back just fine. Internals are fixed by screws. Other Mi USB power banks from 2 line (2c, 2i) are built in same way.
Described USB power bank have good charging capacity and is easy for everyday use. Keep in mind that design is not rugged and battery terminals inside are thin metal strips. Try to avoid dropping it on hard surfaces. Kid admitted that he droped his power bank several times - hard to hide dents at outer case corners :)
Xiaomi Mi Power Bank 2S appeared easy for basic repairs. Glued parts are easy to remove and they stick back just fine. Internals are fixed by screws. Other Mi USB power banks from 2 line (2c, 2i) are built in same way.
Described USB power bank have good charging capacity and is easy for everyday use. Keep in mind that design is not rugged and battery terminals inside are thin metal strips. Try to avoid dropping it on hard surfaces. Kid admitted that he droped his power bank several times - hard to hide dents at outer case corners :)
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Pretty straight forward tutorial, I wish i had the tools to repair it, I have it since 2018, never really used it, and now when I tried to charge it , the lights blink for a sec and then nothing. I wish I could get a replacement for free but the warranty has expired since 2019. I will probably take it for recycling unless I find someone to give it to.
Lithium batteries self-discharge during a year or two. Few years without charging obviously left power bank with battery voltage so low that charging controller refuse to charge it - it have upper/lower voltage treshold and normally doesn't operate if voltage is too high or too low. There is no other way than disassembling and charging the battery from outer 3.4V voltage source with controlled current level - like laboratory power supply. When battery is charged to 3.4V in such way, original power bank controller will be able to charge it completely again.
