Battery not detected on assembled Framework Laptop 13 with AMD 7840U

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I have assembled a Framework Laptop 13 from second hand parts, with the AMD 7840U Mainboard, the chassis, the input cover, the Chromebook Edition screen/camera/mic, and the 55 Wh battery. I didn’t get the speakers and the audio board because they are hard to find and I usually use a Bluetooth headset to listen to anything. Then I met the problem:

The battery is not detected in Windows 11, Linux (NixOS unstable) and even the BIOS update session (initiated from Windows, updating from 3.05 to 3.07). Also, it provides power, but does not charge, and I have already got an empty battery. I’m sure the pins are straight, not bent.
Edit: Not sure if the normal battery is being charged. Maybe it’s only unable to charge when the battery is completely empty.

On Linux, sudo dmesg | grep battery says:

[   10.361810] ACPI: battery: Slot [BAT1] (battery absent)

while the battery connector is physically in place.

Initially I thought it must be the problem of the battery, so I tested with another battery from a friend, but it was still not detected. (I removed the battery soon so that it wouldn’t become another dead brick.)

Then I had a look at the battery documentation, tested the pins of the battery connector, with the battery connected, and found that SYS_PRES is always low, even if the system is running. I wonder if this means something is wrong.

Also, I noticed that Framework Laptop 13 with AMD 7840U would come with the 61 Wh battery if purchased from frame.work directly as a whole. Does the Mainboard actually support the 55 Wh battery?

Currently the BIOS version is 3.07, updated using stanalone mode as the updater refused to update because the battery was not detected.

P.S. This is not a Linux-only issue, so I didn’t tag Linux.

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This is probably the mainboard failing to tell the battery that the system is connected/on.

I suspect this is a damaged mainboard. Can you test if there is a short between the SYS_PRES pin and GND or if the pin is just floating?

Of course.

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The pins doesn’t seem to be shorted, at least when the battery is not connected (I don’t think it is safe to test it with the battery connected). And I don’t know how to test whether it is floating…

By the way I’m actually not sure whether the battery is charging as I don’t have a way to figure it out. Maybe it is just not able to charge when the battery is completely empty.