I bought this D54250WYK s/h and it had the 'CMOS time not set' message on boot up. Found the battery was flat but after replacement and date/time set up it was OK, until shutdown or restart.
I have updated BIOS to latest 54 (2019).
On shut down with power adapter still connected, it will start up again with CMOS and Windows showing time it was last shut down. i.e the RTS is not keeping track of time.
If shut down and power removed, on restart, BIOS will show time zero (2012), and windows will still boot up with the time it was shut down.
Not sure what's happening here, if RTS is not keeping time, why/how does Windows remember the last shut down time?
Bottom line is I need to have this NUC boot up with correct date/time.
Check the polarity of the new battery (compare to the old battery). There are cases (for example, the batteries fitting DELL laptops), the wires on the connector are inverted.