How to identify CMOS Battery Failure

CMOS batteryCMOS stands for Complementary Metal Oxide Semiconductor and it is a technology used to build up microprocessors, microcontrollers and other digital logic circuits. The CMOS is usually powered by a CR2032 cell battery known as the CMOS battery. It stores the day, time and month on your PC and it keeps the correct details, even after you shut down your computer for an extended period of time. This ensures that you get the correct time and date when you use your PC again, but the main function of the CMOS battery is to store the BIOS settings of your computer.

The BIOS allows the system to recognize the hardware that is available and the device drivers that can be used. If there are performance issues with the CMOS battery, the BIOS doesn’t get all the data it requires and the computer would not work as it should. There are a few signs that will make you aware of CMOS battery failure, here is what you may come across with:

1. One of the indicators of CMOS battery failure is that your PC turns off or doesn’t start sometimes. If the drivers stop working, this could also be related to CMOS.
2. Getting “CMOS checksum error“, “CMOS read error” or other similar notifications while booting.
3. Hardware issues are also a sign of CMOS battery failure. You may also notice that your computer is having trouble to recognize the keyboard, the mouse or the printer.
4. If your computer has the incorrect date and time settings, it may be due to CMOS battery failure. Additionally, you may notice that the date/time is constantly being reset even after you have fixed these in the BIOS.

How to replace the CMOS battery

The majority of CMOS batteries would last up to 10 years (the lifetime of a motherboard), but in some cases it may need to be replaced before that. Once you have ascertained that there is a problem with the CMOS battery, you will need to remove it from the PC to replace it. In order to avoid further issues, it is important to make sure that the battery you get is the correct one. This will require you to open your PC (unplug it first) to take the battery out.

1. The CMOS is a small, round battery, similar to the ones used in some watches. You will find it in a holder on the motherboard.
2. After locating the battery, you can write down its details to make sure that you get the same type of CMOS, or bring it along with you when you go shopping for a new one. If you can’t find the exact same battery, try at least to get the closest match available with the same voltage.
3. When you have the battery, place it in the motherboard and start your PC. If the time/date settings are correct and the PC can locate the hardware, the CMOS should be working.

If you don’t feel comfortable opening your PC to remove the CMOS for fear of causing any damage or need help to identify the CMOS battery, you can bring it to a trusted PC repair shop for assistance.
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