ThinkPad T490s only starts with battery

Collapse
X
Collapse
 
  • Page of 1
  • Time
  • Show
Clear All
new posts
Previous template Next
  • rumpumpel1
    Senior Member
    • Jul 2019
    • 165
    • germany
    #1

    ThinkPad T490s only starts with battery

    I am testing a ThinkPad T490s with this setup: only the bare mainboard NM-B891 with a fan and the small Power-On daughterboard as well as with a USB-C monitor (no BIOS battery!).

    If I connect a battery, the mainboard starts up normally. After about 50 seconds the logo appears and after another 30 seconds the final message “... System configuration is invalid. Press Esc to continue or F1 to enter setup”.
    If I connect the power supply unit instead of the battery, a USB meter shows the usual fluctuating power consumption for approx. 30 seconds, then the mainboard switches off (power LED goes out). The USB-C monitor shows no image.

    If I connect the battery and power adapter, the Lenovo logo flashes briefly on the monitor after a while, but the final message does not appear as in the case of the battery. The USB meter only shows a few mA the whole time, so the battery is not being charged either.

    What could be the reason for this?


    schematisc and boardview can be found here:​
    Tags: None
    • mon2
      Badcaps Legend
      • Dec 2019
      • 14720
      • Canada
      #2
      What is the voltage showing on your USB-C meter? Is it 20V or stuck @ 5V?

      20V is required for a normal boot cycle. 5V is the power on default by the power delivery (PD) adapter.

        Comment

        • rumpumpel1
          Senior Member
          • Jul 2019
          • 165
          • germany
          #3
          The voltage is 20V.

            Comment

            Previous template Next

            Related Topics

            Collapse
            • Bowline
              Dell E6400 PT434 type Battery Charging Stuck at 1%. Battery Pinouts?
              by Bowline
              My question pertains to understanding the control circuity inside a Dell PT434 type battery used in Dell E6400, E6410 and other Dell notebooks?

              Does anyone have a circuit diagram for the inside of a Dell PT434 battery and/or a description of how the control lines work to control this battery?

              My reason for asking is I have a battery which I cannot get to charge beyond 1% in a Dell E6410 or E6400.
              The LED bar graph charge indicator on the battery shows one LED lighted when the info button is pressed.
              I have tried multiple different Dell power adapters. My Dell...
              06-11-2025, 10:13 AM
            • Genghis_Khan
              ThinkPad T470p – CMOS Checksum Error Persists After Main Battery Removal (even with new CMOS)
              by Genghis_Khan
              Hello everyone,

              I’m currently troubleshooting an issue on my Lenovo ThinkPad T470p (Type 20J6) and would really appreciate any insights or solutions.

              Issue summary:

              Whenever I remove the main laptop battery and AC adaptor, then place them back, the system gives a “CMOS checksum error” at next boot, and the BIOS clock resets to its default time/date.

              However, the RTC works fine as long as the main battery remains attached — even if the laptop is unplugged for hours. Same as I remove the battery while the AC is attached, RTC remains. Obviously,...
              11-11-2025, 11:51 AM
            • Spider28
              Thinkpad T490s No battery recognize
              by Spider28
              I just bought a new T490s battery. The Lenovo Diagnostic said no battery. Open check the battery socket from motherboard it shows no voltage should be 11-12V. The usb-c power adapter had 20v and the laptop came up with ac adapter plug in. What should I check next?
              02-16-2024, 07:33 PM
            • Grafnus
              Lenovo ThinkPad P15 Gen2 Battery Mosfet Replacement
              by Grafnus
              Hey there,

              first time posting here. I have been lurking a bit trying to find a solution but with little to no avail.

              So I have a Lenovo ThinkPad P15 Gen2. When I got it (for free) it was turning on but not charging because the battery was unplugged. When I plug the battery in, the Laptop won't boot at all.

              Specs:
              • Type: Lenovo ThinkPad P15 Gen2 20YQ-001KGE
              • CPU, GPU, RAM work fine (not involved in the Problem)

              So the first thought was to toss the battery and get a new one, as clearly the BMS is throwing errors or something.

              Now I noticed...
              08-06-2025, 11:54 AM
            • mkdj
              ASUS X571 no power : battery issue?
              by mkdj
              Hello everyone,

              Mark and model: ASUS X571
              Symptoms: not turning on. There is only the LED battery indicator working. The owner of the laptop told me this problem arrived one week after having changed the battery. He then managed to power on the laptop only once, and then it never powered on again.

              Tests already made:
              - Battery is charging when laptop is plugged in. The LED battery indicator turns white after a couple of hours of charge, indicating that battery is fully charged. However, laptop won't turn on anyway, with or without AC plug.
              - I have removed...
              07-14-2025, 09:16 AM
            • Loading...
            • No more items.
            Working...