CMOS 502 Error driving me crazy.

[imDCStar]

Keep getting CMOS error 502.

1. With adapter only (battery disconnected) and battery connected. - CMOS Error 502.
2. On battery only. - CMOS Error 502.

When i press enter system simply off and cycle repeats. It started with a black screen before OMEN logo would show up after pressing power button. With time, the delay between black screen and omen logo increased to 3-4 minutes. I removed ssd and rams also and tested without them. Nothing changed. I flashed latest bios when it was working. 

Not sure if it is battery or else. Because if it is battery only, then it should have worked without battery connected and turned on with AC adapter only.

[Jerry_57]

Hi @imDCStar,

Welcome to the HP Support Community.
 

Thank you for posting your query. I will be glad to help you.
 

The CMOS 502 error combined with the boot delay, black screen before the OMEN logo, and repeated shutdown loop usually points to a BIOS/CMOS initialization issue, a failing battery, or a hardware problem affecting the system's power management.
 

Regarding your question: If the CMOS battery alone were the issue, the notebook would normally still boot with the AC adapter connected. Since the error occurs on both AC power and battery, the cause may be a corrupted BIOS state, a faulty main battery, or a motherboard/power circuit issue.
 

Try the following:

1. Perform a BIOS/CMOS reset:
   
   
   • Turn the notebook off.
      
   • Hold Windows + V, then press and hold the Power button for 2–3 seconds.
      
   • Release the Power button while continuing to hold Windows + V until the CMOS Reset screen or beeps appear.
      
2. Test with the internal battery disconnected:
   
   
   • Disconnect the internal battery from the motherboard.
      
   • Connect only the AC adapter and try to power on.
      
   • This helps determine whether the battery is causing the power issue.
      
3. Inspect the main battery:
   
   
   • A failed or shorted battery can prevent proper system initialization and repeatedly trigger the CMOS 502 error. If the battery is defective, replacement is recommended.

If the notebook still shows the CMOS 502 error after these steps, the issue is likely hardware-related (such as the motherboard or power management circuitry), and the notebook will require service.

I hope this helps.
 

Take care and have a good day.