CMOS Error 502 - Laptop not booting without AC adapter

[SteveMiracolo]

Hello there!

I'm currently experiencing a problem with my Hp Pavilion 14. In the last two or three months, my notebook would turn off abruptly, and wouldn't turn back on without its AC adapter. Every time I turned the notebook back on, I'd see a CMOS Reset (502) error in the BIOS.

The Service Center I contacted told me that my specific model had no CMOS battery installed, and that the CMOS Reset error in this case meant that something was wrong with the notebook's motherboard.

Now, the notebook won't even start by itself - I always need to plug the AC adapter in before pressing the power button.

Is there anything I can do to solve this problem? Could it really be stemming from my notebook's motherboard?

[Huffer]

Since it is a closed battery system the main battery is also the CMOS/RTC battery so if the main battery goes dead, BIOS settings will not hold. 

Service Manual 

The laptop is of the age where you would expect the battery to be needing replacement.