CMOS Checksum is Invalid (Error 502) – Need help finding CMOS battery

[Ak23_]

Hi,

I am using HP Notebook - 15-da0299tu and I keep getting this message on startup:
“CMOS Checksum is Invalid (Error 502).”

I replaced my main laptop battery in December 2024, but the error still appears.

I tried to open the laptop to find the CMOS battery, but I could not locate it.
Does this model have a CMOS battery, or is it integrated on the motherboard?

Please tell me what I should do to fix this issue and how to reset or replace the CMOS if needed.

Thank you.

[Paul_Tikkanen]

Hi:

Your notebook does not have a CMOS/RTC battery.

The main battery also serves as the CMOS/RTC battery to maintain the BIOS and system clock settings.

Below is the link to the service manual.

HP 15 Laptop PC Maintenance and Service Guide

Chapter 3 has the list of parts.   You will not find a CMOS/RTC battery part number.

Chapter 6 has the component replacement procedures.  You will not find a procedure to remove or replace a CMOS/RTC battery.