Thinkpad T450s fails when second battery is inserted.

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  • VikingOy
    New Member
    • May 2020
    • 4
    • Norway

    #1

    Thinkpad T450s fails when second battery is inserted.

    Scenario1: No AC attached. Internal Battery (1) charged and connected. External Battery (2) removed = No issues! Boots into windows OK.

    Scenario2: Powered off. Insert external battery (fully charged). No AC connected. PC enter a never-ending boot loop.

    Scneario3: Powered off. Both batteries attached and charged (70-80%). Connect AC. Power on. Everything seems ok. Boots into windows. Runs just fine. Charging icon and battery status in windows taskbar looks good for both batteries. Both are confirmed taking charge as the percentage increase steadily. Device Manager reports everything OK.
    Then I pull the AC plug, and the PC immediately powers off - bang!

    Could it be a Windows driver issue? No. Exactly the same thing happens if I only enter into BIOS, and then pull the plug.

    Then I tried swapping both batteries from another Thinkpad (same model). The problem does not follow the batteries, but remain with my PC.

    Summary: if I just stay away from an external battery - everything works perfectly as normal, with or without AC connected. I can plug and unplug AC while in windows. Everything Ok.

    As soon as a second battery goes in - everything goes crazy like described above.

    Has anyone ever seen anything like this before?

    Does anyone have any good tips on how to dig to the bottom of this problem and find the solution?

    (I have tried all the obvious things like; Remove the internal battery and The CMOS RTC battery, and hold down the power button, and yes, BIOS is updated to the last version).

    It looks to me as if the PC is unable to be powered from the second battery. But why? The battery is brand new and it works ok in another PC (same model).
  • caspian
    Badcaps Legend
    • Oct 2015
    • 1589
    • Laptop

    #2
    Re: Thinkpad T450s fails when second battery is inserted.

    It seems an IC on the laptop's mainboard got defective. If it is possible, do not use the external battery.

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