VivoBook Flip 14 - Battery installed, but not found

[RangerZ]

I have an ASUS TM420U-WS51T (VivoBook Flip 14)

The machine appears to boot normally and then after about 30 seconds turns off.  During boot, the battery indicator icon alternates between a charging indicator and then an empty battery with an X in it.  Once booted the Battery indicator does not show in the system tray nor is it available in Settings => Preferences.

Things I know or have tried

• In device Manager, the ACPI driver is not shown, but can be seen when hidden\non-present devices are enabled. It can be deleted and returns after next boot, but hidden.
• MyASUS in WinPE indicates the battery is not present. MyASUS in Windows does not offer a battery test.
• After opening the case and disconnecting the battery cable, the machine works normally.
• The BIOS is 2.04 but can not be updated without a battery present and a minimum charge value of 20%, though not likely relevant.
• I have run SFC /scannow and DISM Resotre health. After the former, the machine booted correctly, however after a Windows update it reverted to the prior behavior. I had one other situation where the hardware seemed to behave, but after disconnecting and reconnecting the power it did not.
• I have tried a hard reset with the power button (hold for 40+ seconds) with no improvement.
• The PC does NOT crash in the Windows RE environment, but does crash with a Win PE USB attached (Win10XPE).

The battery was running the device for about 6hrs IIRC. It then sat for some time (2-3 mos) and has been problematic since.

The boot behavior and indicators are NOT consistent, in my mind with a failed battery. This typically presents an icon that does not charge and the PC runs normally with power connected.

I am willing to replace the battery, but would like to first validate the battery as the issue.

Does anyone know where\how to purchase this part (ASUS B31N1911).

[Falcon_ASUS]

@RangerZ 
According to your description, it is indeed possible that the issue you are experiencing is caused by battery aging or a malfunction.
I would suggest you bring back your laptop to our service center for further confirmation.
The following is the contact information:
https://www.asus.com/support/service-center-location 
Also you can contact the local service center for help.
The following is the contact information:
https://www.asus.com/support/CallUs#
Sorry for any inconvenience it may be caused.

[RangerZ]

Thank you for your reply, but as expected, after talking to ASUS\Microcenter support, depot service on this item is not cost effective.

Other than replacing the battery for about $50, it makes little sense to spend money on this PC and even then it would be preferable to have some more concrete idea of the battery's health.

I was hoping that someone might know if the failure description above is a verified failure mode for the battery or if this failure path indicates other issues.

I was also hoping that there might be some information regarding the battery pin out that could be used for at least Go\No Go testing of the battery itself.                   

[Falcon_ASUS]

@RangerZ
I think I can currently provide you with the following for your reference:
[Notebook] Troubleshooting - How to fix the battery cannot provide power/be charged, or be fully cha... 
Sorry for any inconvenience it may be caused. 

[RangerZ]

Thanks for the ref, but I actually have been through this.

1 - AC adapter appears ok and runs computer correctly with battery unplugged
2 - Reset done, with no change in operation
3 - Unable to update the BIOS. PC indicates it cannot proceed with less than 20% battery power AND AC adapter connected.
4 - BIOS Reset - Done with and without battery connected.  No change in operation
5 - Battery Diagnostics - Battery not found so it will not proceed.
6 - I set show hidden devices and removed the ACPI Battery device and it reinstalled on next boot with no change in operation.
7 - Battery cannot be fully charged is not relevant as the battery cannot be found

Interestingly it does not appear there is a BIOS battery (coin cell) in the device.  While the PC does not reset itself to 1999 or such, it does seem to not track time when not connected to AC.  I expect the last time is written to NVRAM and, if the battery were available, would continue to track time. When running and online, Windows will correct the time. I guess the design saves a couple dollars and in general would work between the battery and Windows NTP and only should need correcting in the case of a failed(?) battery.

Any suggestions on obtaining an ASUS battery in the US? Microcenter will not sell me one unless they install it.