ASUS X54H laptop thinks it's always charging even with charger unplugged

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  • m1ch43lzm
    replied
    Boardview here
    https://www.badcaps.net/forum/troubl...-2-1-boardview

    From the datasheet of BQ24740 there's a voltage divider connected to pin 5, the output of it should be around 2.6V with charger plugged in
    ACDET Adapter detected voltage set input. Program the adapter detect threshold by connecting a resistor divider from
    adapter input to ACDET pin to AGND pin. Adapter voltage is detected if ACDET-pin voltage is greater than 2.4 V
    Measure both resistors circled in red (with power removed), the one in parallel with the cap goes to GND, the leftmost one the other end goes to the charger input, maybe one of them is out of spec
    Measure voltage at ACDET, marked with a blue line on the picture:
    1. Only battery connected
    2. Charger connected

    Unfortunately there's no schematic available and the "repair guide" is useless for this, you have to calculate the voltage divider with Voltage=19V and the measured resistor values
    The values from the typical application circuit of the BQ24740 may not match what ASUS used
    Keep one of the resistors, then calculate the bottom one with Out=2.6v, then match it to the closest 1% standard value

    EDIT: Actually the boardview has the values:
    PR8803: 330K
    PR8802 (parallel to the cap): 53.6K
    Attached Files

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    Last edited by m1ch43lzm; 06-24-2025, 07:16 PM.

    Leave a comment:


  • ASUS X54H laptop thinks it's always charging even with charger unplugged

    The charging indicator light on my ASUS X54H laptop is always on even when the charger is disconnected.
    Click image for larger version  Name:	charge light on with charger unplugged-.JPG.png Views:	0 Size:	6.46 MB ID:	3666753
    Windows also shows ''Plugged in'' when charger is not connected.
    Click image for larger version  Name:	Windows shows Plugged in with charger unplugged.jpg Views:	0 Size:	1.74 MB ID:	3666754
    This problem started year ago gradually, when unplugging the charger the charging light took several seconds to disappear, then minutes, and now almost always on even when unplugged for an entire day.
    Strangely, before sometimes immediately when plugging in the charger the charging light went away, and later came back with it connected.
    If I let battery run out and say it has 3% Windows will warn me to plug in the charger, and even if I do, the computer shuts down as if the charger isn't connected, even though the charge light is on!
    Sometimes the charging light flashes green and red alternatively which I think means some fault, but replugging the battery fixes it.
    As you see very weird behavior.

    The problem is the same whether the computer is turned on or off the charging light stays on.

    Some things I tried:
    In Device Manager uninstalling Microsoft ACPI-Compliant Control Method Battery and restarting.
    I measured RTC battery and it was a bit low 2.96V so I replaced it and it didn't help.
    I have two laptop batteries and the problem is the same on both.

    I think the problem is on the motherboard.
    How to troubleshoot it?

    Label on laptop bottom says
    MODEL: X54H
    MB Ver. X54HR
    but printed on motherboard K54LY REV 2.1

    Attached Files

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