my laptop turns off at 80% of battery and restart with error 502

[martibrb]

Hello! My notebook hp pavilion x360 four months ago started to arrest when the battery was 50% and only when I charged it could restart but showed me this message: THE CMOS CHECKSUM IS INVALID…..CMOS RESET (502).

Now the notebook shuts off at 80% so it’s impossible for me to use it normally and I don’t know if buying a new battery could help or not (I already changed the battery one year ago and this one is not original). I tried to update/refresh BIOS but the system says to me it’s impossible and on the official site I can’t download my bios because the only available operating system is windows 10 while my notebook has windows 11.

 

(i’m not english sorry if I made mistakes)

[Garp_senchau]

@martibrb, Welcome to HP Support Community,

Thank you for posting your query; I’m here to help by guiding you through steps to resolve this issue

Hi! Thanks for your clear message—and no worries, your English is great, and I fully understand the situation. Let’s go step by step to figure out what’s happening with your HP Pavilion x360 and how to fix it.

Replace the CMOS Battery

This is a small coin-cell battery inside the laptop.

If you're comfortable opening the laptop, you can do this yourself.

Or, ask a technician to do it—it’s a low-cost repair that often fixes CMOS checksum problems.

Reset BIOS Settings

Try entering BIOS (usually by pressing F10 or ESC at startup).

Once inside BIOS:

Choose “Restore Defaults” or “Load Setup Defaults.”

Then Save & Exit.

This can sometimes fix odd power issues.

Also, refer to these guides for further troubleshooting steps: 

HP PCs - 500, 501, or 502 error displays on a black screen | HP® Support

HP Desktop PCs - Resolve BIOS ROM or CMOS checksum error | HP® Support

I hope this helps.

Please feel free to reply here if you have any questions or if you need further clarification on any of the steps. 

Take care and have a good day. 

Did we resolve the issue? If yes, please consider marking this post as "Accepted Solution" and click "Yes" to give us a helpful vote - your feedback keeps us going!

Regards,

[martibrb]

I tried to open my laptop but I didn't see the CMOS battery and then searching online I found out that my model doesn't have it (HP Pavilion x360 14-dh0023nl).

I tried to reset Bios settings  but it tells me "Unable to open bios signature file" and hp support assistant says that bios is updated. The official website doesn't give me software or driver because my laptop is updated to Win 11 and there it's available only Win10.

Day by day the laptop turns off at an higher percent of battery (2 months ago it turned off at 45-50% while today at 85%).

[Garp_senchau]

Hey @martibrb,

Thanks for reaching out! I suggest you reach out to the nearest HP Authorised service center for personalized assistance. They can provide one-on-one help to fix the problem.

Note: There might be a nominal charge for the service they provide.

HP® Service Center Locator - United States | HP® Support

Regards,