Most definitely the battery (or its connection to the board). The BIOS settings are stored in flash memory, so they are non-volatile and not affected by the loss of the battery backup.
Historically, the BIOS settings were indeed stored in battery-backed CMOS memory (which also maintained the current date and time) and these settings would be lost if the battery failed or was disconnected. When the storage of the BIOS and other firmware switched from EEPROM to flash memory, the storage of BIOS settings switched from CMOS to flash memory as well.
I am often asked why, if the CMOS memory is no longer used for BIOS settings, does the clearing of CMOS make a difference to BIOS operation. Well, pure and simple, the BIOS code contains bugs that retain dependencies on the CMOS contents. Sad to say, they have been looking for these bugs for years but have never been able to find them.
I suggest that you verify that the battery is properly connected to the board. If it appears to be, then the battery will need to be replaced...
Try to access the BIOS and set it to defaults, you can press F9 when you’re in the BIOS and the then press F10 to save all your changes and see how it goes after that.
Sorry for not getting back to you until now. Life has been hectic and obviously having the clock reset itself easily isn't a huge concern if my power hasn't gone out. I finally opened up my NUC today after updating to the latest BIOS. I looked at the CMOS battery and it is connected. Of course when I plug my NUC back in and power it on, I get a battery failure warning (same as before) and once again the clock has reset itself.
So I guess the battery is dead? I just find this strange. This NUC is less than a year old. Meanwhile my 7 year old desktop seems to be keeping time just fine.
Would a battery replacement be covered under warranty?
Unfortunately, I do not believe that Intel's offers support for replacing this separately. You likely have to replace the whole unit. Regardless, contact Intel Customer Support directly to arrange this. Sorry I cannot provide a link, I am away from home currently.
If you feel like you want to replace the battery you can follow the steps here:
This battery can be purchase from different authorized resellers.
Note: CR2032 batteries with a wire and Molex connector might not be locally available. Search the Internet for CR2032 with wire or CR2032 with connector to find an online retailer.
If you want to replace the whole unit for this failure you can contact support here: