Signs of CMOS Battery Failure


The word CMOS is an acronym for “complementary metal oxide semiconductor”. The CMOS battery is a small, round battery that lets you store the day, time, and month on your computer. It allows you to shut your PC down for an extended period of time and still have the correct time and date in place when you use your PC again. More importantly, the CMOS battery stores the BIOS settings of your computer. The BIOS enables us to identify what hardware is on the system and what device drivers to use. When the CMOS battery is weak, the BIOS loses data and the computer can start to malfunction. Let’s take a look at a few signs of a CMOS battery failure.

  1. Incorrect computer date and time settings. Also, the date/time keep getting reset even after you fix them in the BIOS. This is the most common CMOS battery failure sign.
  2. Your PC occasionally turns off or doesn’t start.
  3. Drivers stop working.
  4. You may start to get errors while booting that say something like “CMOS checksum error” or “CMOS read error”.
  5. Some weird hardware issues such as your computer not being able to locate the mouse, keyboard, or printer.

Replacing a CMOS battery

The key to replacing your CMOS battery is making sure you purchase the correct battery. You will need to open up your PC to get to the battery. Make sure to unplug the computer before opening it up.

Next, remove the CMOS battery from the motherboard. It will look like the picture at the beginning of this post and will be in a holder on your motherboard. After you have the battery, you can either write down all the information listed on the battery, or you can just take the battery with you when looking to buy a new one. While at the store, try to find the closest possible match. Try to get a battery with the same voltage.

After you have purchased the battery, just snap it into your motherboard and you should be good to go. You will know right away if it worked based on the behavior of your date/time settings.

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