Laptop shuts down suddenly at 40% charge and upon plugging in shows CMOS Reset 502 everytime

[AnuragV]

Hi HP Community,

 I noticed that my laptop suddenly shuts down when the capacity is at around 40% .  

Upon pressing the power button, it does not startup. But once it is plugged in, the laptop starts upon pressing the power button.  There is a black screen showing the message ' CMOS checksum is invalid......... CMOS Reset (502)'. I press enter and the windows is up in few seconds. I check the battery , it's not discharged.  The time shown on my system is from when laptop went off. The time resets in few minutes . This is a recurring issue, for last 2 weeks.  I have had a recent update on my Windows 10 Notebook on 15th Aug. Thereafter , I noticed  I did not have this issue before the recent update.

Here is what I have done so far from my end to solve this:

• Opened the laptop base, unscrewed the battery and tried to locate the CMOS battery ( to replace it ), but could not find it.
• Entered the BIOS settings, loaded default BIOS , saved changes  and booted the laptop.
• Tried running Component Testing on Battery and Adapter , pressing F2 on BIOS windows --> Power --> Battery. There is no problem with the battery. Just needs some calibration , it seems ( I think because I installed a new one in Jan this year)
• Powered off the laptop, disconnected all power sources, pressed power button for about 15 secs. Then plugged in the adapter and started the laptop

[Sneha_01]

Hi @AnuragV,

Welcome to HP Support Community.

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

The issue you're experiencing with your laptop shutting down unexpectedly, showing the CMOS checksum error, and requiring power connection to start up points to a couple of potential problems. Here’s a detailed approach to diagnosing and resolving the issue:

1. Check CMOS Battery

Since you couldn't locate or replace the CMOS battery, let’s clarify some details:

• CMOS Battery Location: On many laptops, the CMOS battery is not easily accessible and is often embedded on the motherboard. It might require removing the motherboard or specific panels to access it.
• Battery Replacement: If you are comfortable, you could consult the laptop’s service manual for the exact location and replacement procedure of the CMOS battery.

2. Verify Battery Health

• Battery Calibration: Even though you tested the battery and it seems to work fine, calibrating the battery might help. To do this, fully charge the battery, then let it discharge completely until the laptop shuts down by itself, and then fully charge it again.

3. Check Power Supply and Battery Connection

• Verify Battery Connection: Ensure the battery is securely connected. Sometimes, a loose connection can cause issues.
• Inspect Power Adapter: Check if the power adapter and charging port are functioning correctly. Sometimes, issues with the power adapter can cause similar symptoms.

4. Perform a Hard Reset

You mentioned performing a reset, but it’s worth repeating to ensure all power-related issues are cleared:

• Power Drain: Disconnect all power sources, including the battery if possible. Press and hold the power button for 15-30 seconds to drain any residual power.
• Reconnect Power: Reconnect the power adapter and battery, then attempt to power on the laptop.

5. Update BIOS

• Check for BIOS Updates: Sometimes, a BIOS update can resolve issues related to power and CMOS settings. Visit the laptop manufacturer's website to see if there’s a BIOS update available for your model.
  • Apply Update: Follow the manufacturer’s instructions carefully when updating the BIOS.

6. Check for System and Software Issues

• System Files Check: Run a System File Checker scan to ensure system files are intact.
  • Open Command Prompt as an administrator and type sfc /scannow and press Enter.
• Review Recent Updates: If the problem started after a recent Windows update, it might be worth checking if uninstalling the update resolves the issue.
  • Uninstall Update: Go to Settings > Update & Security > Windows Update > View update history > Uninstall updates.

7. Inspect BIOS Settings

• Reset to Defaults: You’ve already done this, but double-check if the settings related to power management and CMOS are correctly set.
• Check for Advanced Settings: Look for settings related to battery management or power supply in the BIOS.

8. Test with Another Power Adapter

• Try a Different Adapter: If possible, test with another compatible power adapter to rule out issues with the current one.

I hope this helps.

Take care and have a good day.

Please mark this post as “Accepted Solution” if the issue is resolved and if you feel this reply was helpful click “Yes”.

Rachel571

HP Support

[AnuragV]

Hi @Rachel571,

Thank you so much for the suggestions.

I checked the maintenance and service guide for my laptop  and could not find CMOS battery as a major component   https://h10032.www1.hp.com/ctg/Manual/c06140017.pdf

I don't think my laptop has a CMOS battery . Looks like my internal battery is doing that job. Let me know if I'm wrong here. 

I did calculate the degradation on my new battery  - it's around 43 % after only 296 days of usage.  I did this after I noticed that laptop shuts down at 80% power as well. I wanted a suggestion if replacing the battery will make things right. 

I also performed BIOS reset 3 times, did a hard reset twice and also updated BIOS from F12 to F42 ( using HP support assistant) , but I'm still not able to find a way around this. I'm not able to uninstall updates for some reason. 

Thanks again for the suggestions.

[AnuragV · Accepted solution]

Changed the battery and everything is working fine now