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iphone 8 cannot read battery data

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  • iphone 8 cannot read battery data

    iPhone 8 not reading the battery
    1. battery verified(with known good board). motherboard issue?
    bad motherboard
    noticed Q3200 had been ripped off it's pads

    replaced Q3200
    still unable to read battery data
    Pin 2 of battery connector tests OL (should be 0.793)
    I took off the replacement Q3200 and "double diode"(probably was no need to)
    For the Q3200
    seated resistance
    1. GATE(pin 1) 0.308 known good 0.303
    2. SOURCE(pin 2) 0.445 known good 0.454
    DRAIN (pin 3) OL can't measure known good nothing's exposed but since the DRAIN connects directly to the battery pin I assume it should measure somewhere between 0.6 - 0.8
    If I were troubleshooting an open for a backlight cct I would start at the connector and work my way back in until the open disappeared. But that approach doesn't seem to work here.
    Attached Files

  • #2
    When you replace q3200 you should get 0.6-0.7ish at the battery connector. If you don’t, then q3200 is not on there or the pads are torn from the vias underneath.

    You can just run a jumper to close the open—connect the battery data line directly from the connector to the i2c0_sda line and forget about the mosfet. You can leave the mosfet gate open and just let the connection between battery and board be hard wired.


    • #3
      Note—when you hard wire this line the connector diode reading is something like 0.3, not 0.6


      • #4
        My attempts to address the initial problem of Q3200 OL

        where I worked see picture

        multiple attempts allowing the board to cool to comfortable to touch in between

        all components bordered were either dislogded and restored or dislodged, lost and replaced from a donor board

        DCPS 0mA B4 PTB

        DCPS PTB increments up to 110/120mA drops back repeats

        seated resistances(compared to known good)
        • Q3200
        • Q3201
        • battery header
        • R3201

        Conclusion: No short but something has gone bad as a result of my soldering efforts.
        (Note before my attempts to address Q3200 the phone did boot ok - it just had battery level misreads)

        What could I have done working in this area to explain the current behaviour on DC power supply?

        Attached Files
        Last edited by lots2learn; 09-18-2021, 01:58 AM.


        • #5
          It was Q3200. Its seated resistances may have been ok but the mosfet itself was shot. I replaced it with another 'cleaner' looking one from a donor board and now the phone boots fine and properly reads the battery level. (so long as I keep pressing on the battery connector which has now gone spongy!)


          • Jessa_the_Professa
            Jessa_the_Professa commented
            Editing a comment
            Great, you figured it out! You can just use a tweezer to pull the data pins out slightly from the inner middle plastic to rejuvenate the connector.

        • #6
          Looking at your photo, both of those mosfets are "rough" I would not use them. I would just jump the gas gauge lines across the mosfet and not worry about the mosfet gate and leave that open--I do that all the time when the pads are missing from this kind of pry damage. Why is your phone brain dead? It could be the mosfets which are now pulling down the gate line. It could also be overheating at the EEPROM within the trinity chip but I think that would have a longer boot loop.


          • Jessa_the_Professa
            Jessa_the_Professa commented
            Editing a comment
            Apologies--I had typed out this response yesterday but it doesn't appear to have posted on the thread due to a network error.