HP Pavilion x360 15 shuts off at high battery, boots up with CMOS checksum issue

[FSchaef]

Recently, my computer has started shutting off with no warning while I'm using it, no matter what my battery charge is at. This seems to happen the most when it's not charging.It doesn't die immediately if I unplug the charger-- it seems to die at a random time after, but usually less than an hour. This has happened at different times with the battery at 30%, 40%, 50%, even 95%.

When I try to boot it up after, it displays the message "CMOS checksum invalid" on a black screen. If I hit enter to boot it from there, it'll get stuck in a boot loop, unless I plug it in to the charger. If it's plugged in to charge, it breaks the loop and boots up to a usable state (though it won't let me use my PIN to log in as usual).

I don't know what's happening. I just got a battery replacement one year ago, and I'm generally pretty good at not leaving my laptop charging at full 100% battery too long.

I ran the PC diagnostics, the BIOS is up to date. I even tried a manual BIOS update with drivers I downloaded from the HP website, and neither update worked. This model doesn't have a CMOS battery, as the CMOS chip is hooked up directly to the main computer battery. The main computer battery seems like it's working fine, but I haven't opened up the computer yet to check.

What on earth is going on? This is unacceptable and other HP support outlets have been absolutely no help so far.

[Max3Aj]

Hi @FSchaef, Welcome to HP Support Community. 

Thank you for posting your query, I will be glad to help you. 
It sounds like your HP Pavilion x360 15 is experiencing a power management or BIOS-related issue, potentially caused by a failing battery, corrupted BIOS settings, or a motherboard issue. Let's break down the symptoms and possible causes:

Key Symptoms:

1. Random shutdowns at high battery levels (but mostly when unplugged).
2. CMOS checksum error upon reboot.
3. Boot looping unless plugged in.
4. PIN login fails after reboot.
5. BIOS is already up to date, and a manual reflash didn’t help.

Possible Causes & Solutions

CMOS & Battery-Related Issues

• Since your laptop does not have a separate CMOS battery and instead uses the main battery for CMOS power, the main battery may not be supplying stable voltage to the CMOS chip.
• Even though the battery was replaced a year ago, it may have degraded or become faulty.
• Possible Fix:
  • Try running the laptop without the battery (if possible), only on AC power. If it runs fine, the battery may be the problem.
  • If possible, test with another battery or replace it.

Power Management & BIOS Corruption

• If your BIOS settings are not being retained (causing the checksum error), the CMOS chip might not be getting consistent power.
• The shutdowns could also be due to power delivery issues from the motherboard or battery management system.
• Possible Fix:
  • Perform a BIOS hard reset:
    1. Turn off the laptop.
    2. Disconnect the charger and battery.
    3. Press and hold the power button for 30-60 seconds.
    4. Reconnect the charger (without the battery) and turn it on.
  • Try resetting BIOS defaults:
    1. Enter BIOS by pressing F10 on boot.
    2. Select "Load Setup Defaults" (or "Reset to Default Settings").
    3. Save and exit.

Battery Calibration Issue

• The battery's calibration may be incorrect, causing the system to misinterpret the charge level and shut down unexpectedly.
• Possible Fix:
  • Fully drain the battery until the laptop shuts down.
  • Charge it to 100% while off.
  • Run HP’s Battery Calibration tool from HP PC Hardware Diagnostics (F2 on boot → Component Tests → Battery Test).

Hardware Issue (Motherboard or Power Delivery)

• If power circuits on the motherboard are faulty, the laptop may be unable to switch between battery and AC power properly.
• The CMOS checksum issue could indicate a deeper motherboard problem.
• Possible Fix:
  • Check the battery connector and cables inside the laptop.
  • If issues persist after testing with a new battery, motherboard repair/replacement may be required.

I hope this helps. 

Take care and have a good day. 

Please click “Accepted Solution” if you feel my post solved your issue, it will help others find the solution. Click the “Kudos/Thumbs Up" on the bottom right to say “Thanks” for helping! 

Max3Aj

HP Support