A low CMOS battery refers to a situation where the battery that powers the complementary metal-oxide-semiconductor (CMOS) chip on a computer’s motherboard is running out of power or has already been depleted. The CMOS chip is responsible for storing the BIOS (Basic Input/Output System) settings and maintaining the system clock of a computer when it is powered off.
What is CMOS battery
The CMOS (Complementary Metal-Oxide-Semiconductor) battery is a small battery on the motherboard of a computer that provides power to the CMOS chip. The memory and real-time clock are powered by CR2032 lithium cell. The CMOS battery is about the size of a coin, or similar to the calculator battery.
Low CMOS battery signs
When the CMOS battery is low or failing, or even worst… dead, you may experience the following signs:
- Incorrect date and time: The most common sign of a low CMOS battery is that the computer consistently displays the wrong date and time, even after you have set them correctly.
- BIOS settings reset: The CMOS battery helps maintain the BIOS settings. If the battery is low or dying, the computer may forget or reset the BIOS settings to their default values. This could include settings related to boot order, hard drive configuration, and other hardware settings.
- Boot failures: When the CMOS battery is weak, it can lead to boot failures or difficulties starting up the computer. You may encounter error messages or find that the computer fails to recognize hardware devices during the boot process.
- CMOS checksum errors: A low CMOS battery can cause checksum errors during the startup process. You may see error messages like “CMOS Checksum Error” or “CMOS Battery Low” during boot-up.
- Unstable system behavior: A failing CMOS battery can lead to system instability. You may experience random crashes, freezes, or unexpected behavior while using the computer.
- Inability to save BIOS changes: When the CMOS battery is running low, you may not be able to save any changes you make to the BIOS settings. The settings may revert to their default values every time you restart the computer.
If you suspect that your CMOS battery is low, it is generally a good idea to replace it. CMOS batteries are typically inexpensive and can be found at most computer hardware stores. It’s important to follow the manufacturer’s instructions or consult a professional if you are unsure about replacing the battery yourself.
How to replace low CMOS battery
WARNING: Before working inside your computer chassis, ground yourself by touching the grounded metal case briefly to dissipate any built-up static electricity. Or, wear an anti-static wrist bracelet, if you have one.
To address a low CMOS battery situation, you can follow these steps:
- Shutdown your computer. Start by turning off your computer completely.
- Locate the CMOS battery: Open your computer case and look for a small coin-shaped battery on the motherboard. It is usually a silver or black battery, similar to a watch battery.
- Remove the battery: Gently remove the CMOS battery from its socket. You may need to use a small flathead screwdriver or your fingers to carefully pop it out.
- Wait for a few minutes: Leave the battery out of its socket for about 5 minutes. This allows the residual charge in the motherboard’s capacitors to dissipate.
- Replace the CMOS battery: Insert the battery back into its socket, ensuring the correct orientation. The positive side (+) should face up.
- Close the computer case: Put the computer case back together and secure it properly.
- Power on your computer: Turn on your computer and enter the BIOS setup by pressing the appropriate key during startup (usually indicated on the screen). The key may be Del, F2, F10, or Esc, depending on your computer’s manufacturer.
- Set the date and time: Once you’re in the BIOS setup, navigate to the date and time settings and adjust them accordingly. Save the changes and exit the BIOS.
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Final Thoughts
It’s essential to prioritize safety and seek professional assistance when dealing with computer hardware if you’re uncomfortable or unsure about the process. Computer components can be delicate and sensitive, and mishandling them can lead to damage or even personal injury. Professional technicians have the knowledge, skills, and experience to handle hardware-related tasks safely and effectively, ensuring that everything is properly installed, repaired, or upgraded. Don’t hesitate to reach out to a professional if you’re unsure about any aspect of working with computer hardware. It’s better to be safe and seek assistance rather than risk causing harm or further complications.