What kills CMOS battery and how to replace it?

This article is going to explain what kills CMOS batteries and how to replace them.

What kills CMOS battery and how to replace it?

The CMOS battery (Complementary Metal Oxide Semiconductor) is a small, mainly button/coin cell battery that powers the little memory that holds information about the BIOS settings.

When the CMOS battery dies, BIOS resets all of its settings, including the date, hard drive settings, boot order, and so on, causing the OS to fail to launch properly in many cases. When this occurs, the only option is to replace the CMOS battery.


What destroys the CMOS battery?

CMOS batteries endure 3-10 years on average, and occasionally even longer.

The CMOS battery's drain current is relatively low, but it eventually empties the battery completely, causing the CMOS battery to die.

In addition, when compared to the temperature in a typical office or house, the temperature inside computers is frequently higher, which contributes to a higher self-discharge rate.

As a result of the persistent current drain and rising temperature, the CMOS battery eventually dies.


How to Replace CMOS Battery

If you are familiar with computers, the best course of action is to take your computer to a computer store/service and have the CMOS battery replaced for you - it will cost more than the battery itself, but it will be much less expensive than purchasing a new motherboard, memory modules, processor, and so on.

Back up the BIOS to a USB memory stick if your computer warns you about a low CMOS battery.

If you can't back up the BIOS but are getting warnings about a weak BIOS battery, it is theoretically possible to replace the CMOS battery while the computer/server is turned on, but this is not encouraged - if you do it, remember that everything you do is your responsibility.

To change the CMOS battery, perform these steps:

  1. If at all possible, make BIOS backup
  2. Shut down the computer;
  3. Unplug the power cord and hold down the On/Off button for 10-15 seconds.
  4. Open the computer without touching any of its internal components.
  5. Use the anti-static wrist strap band to ground yourself.


Common CMOS Battery Models

The CR2032 lithium non-rechargeable 3.0V Lithium Manganese Dioxide (Li-MnO2) battery is the most used CMOS battery, while other comparable batteries such as the CR2025, CR2020, and CR2016 are also used.

CR2032 and comparable batteries have a wide temperature range and a low self-discharge rate, allowing them to keep a charge for up to ten years, or even longer.

However, some devices, such as the BR2032, support the use of Carbon-Monofluoride Lithium batteries, which have a label that begins with the letter 'B.'