Lenovo T470P NM-B071P not charging, 20 volts on positive +ve battery terminal

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  • Zibbo
    Badcaps Veteran
    • Mar 2017
    • 201
    • Zimbabwe

    #1

    Lenovo T470P NM-B071P not charging, 20 volts on positive +ve battery terminal

    Lenovo T470P NM-B071P had no power. PQ2 and PQ11 were shorted, repaced them and laptop turned ON. Connected the battery and the motherboard turned off immediately and it won't charge, checked the voltages and found out that there is 20v on the positive battery terminal.
    Replaced battery charger IC PU101 and the two switching mosfets PQ101 and PQ102 and still same problem. Now I can't figure out how 20v is ending up on the battery terminals.
  • mon2
    Badcaps Legend
    • Dec 2019
    • 13848
    • Canada

    #2
    The high side battery charge or the battery enable MOSFET must be leaking. This leak is supplying the main power rail voltage unregulated onto the battery terminal. Remove all power. Measure the resistance across the MOSFET pins to confirm. If the resistance is not hundreds of k ohms, part may be defective.

    Comment

    • Zibbo
      Badcaps Veteran
      • Mar 2017
      • 201
      • Zimbabwe

      #3
      Originally posted by mon2
      The high side battery charge or the battery enable MOSFET must be leaking. This leak is supplying the main power rail voltage unregulated onto the battery terminal. Remove all power. Measure the resistance across the MOSFET pins to confirm. If the resistance is not hundreds of k ohms, part may be defective.
      Thanks but I have already replaced the high side mosfet PQ101

      Comment

      • mon2
        Badcaps Legend
        • Dec 2019
        • 13848
        • Canada

        #4
        Review if PD7 is leaking.

        PQ10 ok?

        Comment

        • Zibbo
          Badcaps Veteran
          • Mar 2017
          • 201
          • Zimbabwe

          #5
          Originally posted by mon2
          Review if PD7 is leaking.

          PQ10 ok?
          Both tested ok, I have also replaced them just to be sure.

          Edit: Thank you mon2 for your assistance, it was my fault. I had replaced PQ11 with a P-Channel mosfet instead of N-Channel. Sorry for wasting your time.
          Last edited by Zibbo; 12-27-2024, 12:48 PM.

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