Have you noticed your Windows 11 computer showing the wrong time or BIOS settings resetting after every restart? These could be signs of a failing CMOS battery. The CMOS battery is a small coin-cell battery on your motherboard that stores BIOS/UEFI settings — and when it starts to fail, your system may act strangely.
In this guide, we’ll walk you through how to check CMOS battery status on Windows 11, explain the warning signs of a weak battery, and show you step-by-step methods to confirm its health.
📝 Quick Summary (Key Takeaways)
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The CMOS battery stores BIOS/UEFI configuration and real-time clock.
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Symptoms of failure include wrong system time, boot errors, or BIOS resets.
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Windows 11 does not directly show CMOS battery health, but you can check status using BIOS, Command Prompt, Event Viewer, and third-party tools.
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If your CMOS battery is weak, replacing it is a quick and inexpensive fix.
What is a CMOS Battery and Why Does It Matter?
The CMOS (Complementary Metal-Oxide-Semiconductor) battery powers the BIOS/UEFI memory even when your PC is off.
Without it:
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System date and time reset after shutdown.
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BIOS settings like boot order or overclocking profiles are lost.
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Your computer may show “CMOS checksum error” at startup.
Signs That Your CMOS Battery is Failing
Here are the most common symptoms:
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Clock and date reset every time you reboot.
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BIOS settings return to default after shutdown.
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Random boot errors or inability to detect drives.
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Beeping sounds on startup (motherboard error codes).
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Slow boot or black screen before Windows loads.
Can You Check CMOS Battery Status in Windows 11?
Windows 11 does not have a direct “battery health” indicator for CMOS. However, you can check indirect signs using system tools.
Step-by-Step: How to Check CMOS Battery Status on Windows 11
1. Check System Time Accuracy
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Shut down your PC.
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Unplug it from power (and remove laptop battery if possible).
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Wait a few minutes to an hour.
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Restart your PC.
👉 If the time/date reset, your CMOS battery is weak.
2. Use BIOS/UEFI Setup
Most BIOS will show battery status.
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Restart your computer.
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Press the BIOS key (often F2, Del, or Esc) during startup.
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Look for CMOS Battery/RTC status under Hardware Monitor or Advanced Settings.
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If it shows Low, the battery needs replacement.
3. Check Event Viewer for CMOS Errors
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Press Win + R, type
eventvwr, and hit Enter. -
Go to Windows Logs > System.
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Look for warnings like:
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CMOS Checksum Error
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Real-time clock lost power
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4. Use Command Prompt to Detect RTC Issues
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Open Command Prompt as Administrator.
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Run:
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Compare the result with your system clock.
👉 If your system resets after shutdown, the CMOS battery may be the cause.
5. Third-Party Tools
Apps like HWMonitor, HWiNFO, or AIDA64 can sometimes show CMOS/RTC voltage levels.
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Healthy CMOS battery voltage = ~3V.
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Below 2.5V = time to replace.
Comparison of CMOS Battery Check Methods
| Method | Ease of Use | Accuracy | Best For |
|---|---|---|---|
| System Time Check | Easy | Medium | Beginners |
| BIOS/UEFI Check | Medium | High | Accurate diagnosis |
| Event Viewer | Medium | Medium | Detecting errors |
| Command Prompt | Easy | Low | Quick check |
| Third-Party Tools | Medium | High | Voltage monitoring |
How to Replace CMOS Battery (If Needed)
If your CMOS battery is failing:
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Shut down your PC and unplug it.
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Open the case (or back panel if a laptop).
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Locate the coin-cell battery (CR2032 in most PCs).
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Gently remove it and replace with a new one.
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Boot into BIOS and reconfigure settings.
⚠️ Tip: Take a photo of your BIOS settings before replacing to restore them easily.
Preventing CMOS Battery Issues
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Keep your PC connected to power — reduces battery strain.
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Replace CMOS battery every 3–5 years proactively.
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Store spare PCs/laptops with occasional power-on to maintain charge.
Conclusion
Checking CMOS battery status on Windows 11 isn’t as direct as checking a laptop’s main battery, but with BIOS tools, system checks, and third-party monitoring, you can easily confirm if it’s failing.
If you notice repeated clock resets, BIOS errors, or boot issues, it’s a strong sign that your CMOS battery needs replacement. Luckily, swapping it out is cheap, quick, and restores stability to your system.
FAQs About CMOS Battery on Windows 11
1. How long does a CMOS battery last?
Typically 3–5 years, depending on usage and system type.
2. What happens if I remove the CMOS battery?
Your BIOS resets to factory defaults, and system time/date will be lost.
3. Can I check CMOS battery status without opening my PC?
Yes — by using BIOS, Event Viewer, or system time checks.
4. Does Windows 11 show CMOS battery health directly?
No, Windows doesn’t provide a direct CMOS battery monitor.
5. What type of battery does most PCs use?
Most desktops and laptops use a CR2032 coin-cell battery.